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BBUUIILLDDIINNGG MMAATTEERRIIAALLSS

AANNDD TTHHEE CCLLIIMMAATTEE::

CCOONNSSTTRRUUCCTTIINNGG AA NNEEWW FFUUTTUURREE

ISBN: 978-92-807-4064-6

Job number: DTI/2563/PA

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The views expressed in this publication are those of the

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omissions that may have been unwittingly made.

Cover photos: Pictures © Unsplash / Caroline Grondin;

Unsplash / Minh Trí; Pexels / Nothing Ahead; Pexels / Anete

Lusina; Pexels / Charles; Pexels / Littlehampton Bricks;

Pexels / DLKR; Unsplash / Heather Newsom; Unsplash /

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BUILDING MATERIALS AND THE CLIMATE: STATUS AND SOLUTIONS

Suggested citation:

United Nations Environment Programme (2023). Building

Materials and the Climate: Constructing a New Future.

Nairobi

Production:

United Nations Environment Programme

For more information, contact:

United Nations Environment Programme

Industry and Economy Division

Energy and Climate Branch

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BUILDING MATERIALS AND THE CLIMATE: CONSTRUCTING A NEW FUTURE

Acknowledgements

“Building Materials and the Climate: Constructing a New Future”

is the product of the generous dedication and extraordinary

investment of numerous individuals, whose knowledge,

expertise and insight helped shape this important body of

work. UNEP acknowledges the contributions made by many

governments, individuals and institutions to the preparation

and publication of this report. Special thanks are extended

to:

Research Team Members:

Rosemary Sarfo Mensah,CSIR-BRRI

Kingdom Ametepe, CSIR-BRRI

Alexandre Bouffard, McGill University

Jaione Aramburu-Stuart, University of Lima

Martha M. Pomasonco-Alvis, University of Lima

Seth Embry, Yale CEA

Dita Zakova, Ecolibri

Juan Skinner, Ecolibri

Reviewers (UNEP):

Sheila Aggarwal-Khan; Yun Cui; Jonathan Duwyn, Pauline

Guérécheau, Yutong Guo, Sophie Loran, Mona Mohammed,

Giorgia Patarnello, Mark Radka, Steven Stone

Reviewers:

Anna Zinecker, Programme for Energy Eciency in Buildings;

Adriana Salazar Ruiz, German Federal Ministry for Economic

Affairs and Climate Action;

Sharon Prince, Grace Farms Foundation;

Nora Rizzo, Grace Farms Foundation;

Paul Bradley, Lendlease Americas;

Ernest Dione, Ministry of Environment and Sustainable Deve-

lopment of Senegal;

Jérôme Bilodeau, Natural Resources Canada;

Cédric de Meeus, Holcim;

Ryan Robert, Holcim;

Donovan Storey, Reall;

Luca de Giovanetti, World Business Council For Sustainable

Development (WBCSD);

Veronica Contucci, WBCSD;

Foster Osae-Akonnor, Ghana Green Building Council;

Kisa Zehra, Royal Institution of Chartered Surveyors;

Sanjay Seth, The Energy and Resources Institute (TERI);

Dr. Rana Veer Pratap Singh, TERI;

Tom Sanya, University of Cape Town;

Elizabeth Wangeci Chege, SEforAll;

Adrian Jackson, formerly WorldGBC;

Oliver Rapf, Buildings Performance Institute Europe;

Ian Hamilton, University College London;

Zslot Toth, Buildings Performance Institute Europe;

Daniel Reißmann, German Environment Agency;

Tilly Lenartowicz, MASS Design Group;

Kelly Doran, MASS Design Group;

James Kitchin, MASS Design Group;

Megan Kalsman, Carbon Leadership Forum;

Meghan Lewis, Carbon Leadership Forum;

Wolfram Schmidt, German Federal Institute for Materials

Research and Testing;

Jason Vollen, AECOM;

Nora Rizzo, Grace Farms Foundation.

Production and launch support: UNEP Communications

Division

Editor: Lisa Matsny, Sharon Benzoni

Cover design and layout: David Andrade

Design and layout: KUDOS Design Collaboratory

Lead Authors:

Anna Dyson, Yale Center for Ecosystems + Architecture

(Yale CEA)

Naomi Keena, McGill University; Yale CEA

Mae-ling Lokko, Yale CEA; Willow Technologies

Barbara K. Reck, Yale School of the Environment

Christina Ciardullo, American Institute of Architects (AIA);

Yale CEA

Overall supervision:

Jonathan Duwyn, UNEP

Sophie Loran, UNEP

Mona Mohammed, UNEP

Contributing authors:

Mohamed Aly Etman, Yale CEA

Hind Wildman, Yale CEA

Frederick Wireko Manu, Council for Scientic and Industrial

Research-Ghana Building and Roads Research Institute

Alejandra Acevedo-De-los-Ríos, University of Lima; Univer-

sité catholique de Louvain

Marco Raugei, Oxford Brookes University

Eero Puurunen

Nzinga Mboup, Worola

Ibrahim Niang, Agence D’Architecture et de Recherche MBN

Daniel R. Rondinel-Oviedo, McGill University

Jaime M. Sarmiento-Pastor, University of Lima

Andrés M. Lira-Chirif, University of Lima

Aishwarya Iyer, Yale School of the Environment

Yuan Yao, Yale School of the Environment

Vicky Achnani, Yale CEA, Carnegie Mellon University

iii

This publication was nancially supported by the government

of Germany.

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BBUUIILLDDIINNGGMMAATTEERRIIAALLSSAANNDDTTHHEECCLLIIMMAATTEE::CCOONNSSTTRRUUCCTTIINNGGAANNEEWWFFUUTTUURREE©2023UnitedNationsEnvironmentProgrammeISBN:978-92-807-4064-6Jobnumber:DTI/2563/PAThispublicationmaybereproducedinwholeorinpartandinanyformforeducationalornon-profitserviceswithoutspecialpermissionfromthecopyrightholder,providedacknowledgementofthesourceismade.TheUnitedNationsEnvironmentProgrammewouldappreciatereceivingacopyofanypublicationthatusesthispublicationasasource.NouseofthispublicationmaybemadeforresaleoranyothercommercialpurposewhatsoeverwithoutpriorpermissioninwritingfromtheUnitedNationsEnvironmentProgramme.Applicationsforsuchpermission,withastatementofthepurposeandextentofthereproduction,shouldbeaddressedtounep-communication-director@un.org.DisclaimersThedesignationsemployedandthepresentationofthematerialinthispublicationdonotimplytheexpressionofanyopinionwhatsoeveronthepartoftheSecretariatoftheUnitedNationsconcerningthelegalstatusofanycountry,territoryorcityorareaoritsauthorities,orconcerningthedelimitationofitsfrontiersorboundaries.Mentionofacommercialcompanyorproductinthisdocu-mentdoesnotimplyendorsementbytheUnitedNationsEnvironmentProgrammeortheauthors.Theuseofinfor-mationfromthisdocumentforpublicityoradvertisingisnotpermitted.Trademarknamesandsymbolsareusedinaneditorialfashionwithnointentiononinfringementoftrademarkorcopyrightlaws.TheviewsexpressedinthispublicationarethoseoftheauthorsanddonotnecessarilyreflecttheviewsoftheUnitedNationsEnvironmentProgramme.Weregretanyerrorsoromissionsthatmayhavebeenunwittinglymade.©Maps,photosandillustrationsasspecifiedCoverphotos:Pictures©Unsplash/CarolineGrondin;Unsplash/MinhTrí;Pexels/NothingAhead;Pexels/AneteLusina;Pexels/Charles;Pexels/LittlehamptonBricks;Pexels/DLKR;Unsplash/HeatherNewsom;Unsplash/EugeneGolovesov;Pexels/AleksandarPasaricBUILDINGMATERIALSANDTHECLIMATE:STATUSANDSOLUTIONSSuggestedcitation:UnitedNationsEnvironmentProgramme(2023).BuildingMaterialsandtheClimate:ConstructingaNewFuture.NairobiProduction:UnitedNationsEnvironmentProgrammeFormoreinformation,contact:UnitedNationsEnvironmentProgrammeIndustryandEconomyDivisionEnergyandClimateBranch1RueMiollis,BuildingVII,75015,ParisFRANCETel:+33(0)144371450Fax:+33(0)144371474BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREAcknowledgements“BuildingMaterialsandtheClimate:ConstructingaNewFuture”istheproductofthegenerousdedicationandextraordinaryinvestmentofnumerousindividuals,whoseknowledge,expertiseandinsighthelpedshapethisimportantbodyofwork.UNEPacknowledgesthecontributionsmadebymanygovernments,individualsandinstitutionstothepreparationandpublicationofthisreport.Specialthanksareextendedto:ResearchTeamMembers:RosemarySarfoMensah,CSIR-BRRIKingdomAmetepe,CSIR-BRRIAlexandreBouffard,McGillUniversityJaioneAramburu-Stuart,UniversityofLimaMarthaM.Pomasonco-Alvis,UniversityofLimaSethEmbry,YaleCEADitaZakova,EcolibriJuanSkinner,EcolibriReviewers(UNEP):SheilaAggarwal-Khan;YijunCui;JonathanDuwyn,PaulineGuérécheau,YutongGuo,SophieLoran,MonaMohammed,GiorgiaPatarnello,MarkRadka,StevenStoneReviewers:AnnaZinecker,ProgrammeforEnergyEfficiencyinBuildings;AdrianaSalazarRuiz,GermanFederalMinistryforEconomicAffairsandClimateAction;SharonPrince,GraceFarmsFoundation;NoraRizzo,GraceFarmsFoundation;PaulBradley,LendleaseAmericas;ErnestDione,MinistryofEnvironmentandSustainableDeve-lopmentofSenegal;JérômeBilodeau,NaturalResourcesCanada;CédricdeMeeus,Holcim;RyanRobert,Holcim;DonovanStorey,Reall;LucadeGiovanetti,WorldBusinessCouncilForSustainableDevelopment(WBCSD);VeronicaContucci,WBCSD;FosterOsae-Akonnor,GhanaGreenBuildingCouncil;KisaZehra,RoyalInstitutionofCharteredSurveyors;SanjaySeth,TheEnergyandResourcesInstitute(TERI);Dr.RanaVeerPratapSingh,TERI;TomSanya,UniversityofCapeTown;ElizabethWangeciChege,SEforAll;AdrianJackson,formerlyWorldGBC;OliverRapf,BuildingsPerformanceInstituteEurope;IanHamilton,UniversityCollegeLondon;ZslotToth,BuildingsPerformanceInstituteEurope;DanielReißmann,GermanEnvironmentAgency;TillyLenartowicz,MASSDesignGroup;KellyDoran,MASSDesignGroup;JamesKitchin,MASSDesignGroup;MeganKalsman,CarbonLeadershipForum;MeghanLewis,CarbonLeadershipForum;WolframSchmidt,GermanFederalInstituteforMaterialsResearchandTesting;JasonVollen,AECOM;NoraRizzo,GraceFarmsFoundation.Productionandlaunchsupport:UNEPCommunicationsDivisionEditor:LisaMatsny,SharonBenzoniCoverdesignandlayout:DavidAndradeDesignandlayout:KUDOSDesignCollaboratoryLeadAuthors:AnnaDyson,YaleCenterforEcosystems+Architecture(YaleCEA)NaomiKeena,McGillUniversity;YaleCEAMae-lingLokko,YaleCEA;WillowTechnologiesBarbaraK.Reck,YaleSchooloftheEnvironmentChristinaCiardullo,AmericanInstituteofArchitects(AIA);YaleCEAOverallsupervision:JonathanDuwyn,UNEPSophieLoran,UNEPMonaMohammed,UNEPContributingauthors:MohamedAlyEtman,YaleCEAHindWildman,YaleCEAFrederickWirekoManu,CouncilforScientificandIndustrialResearch-GhanaBuildingandRoadsResearchInstituteAlejandraAcevedo-De-los-Ríos,UniversityofLima;Univer-sitécatholiquedeLouvainMarcoRaugei,OxfordBrookesUniversityEeroPuurunenNzingaMboup,WorofilaIbrahimNiang,AgenceD’ArchitectureetdeRechercheMBNDanielR.Rondinel-Oviedo,McGillUniversityJaimeM.Sarmiento-Pastor,UniversityofLimaAndrésM.Lira-Chirif,UniversityofLimaAishwaryaIyer,YaleSchooloftheEnvironmentYuanYao,YaleSchooloftheEnvironmentVickyAchnani,YaleCEA,CarnegieMellonUniversityiiiThispublicationwasfinanciallysupportedbythegovernmentofGermany.AcknowledgementsiiiAbbreviations&KeyTermsviFigures,TablesandBoxesviiEXECUTIVESUMMARYix1BUILDINGMATERIALSARESETTODOMINATECLIMATECHANGE1.1TheBuiltEnvironment’sImpactonGlobalCarbonEmissions11.2WeUsedtoBuildwithLow-CarbonMaterials21.3StructureoftheReport42DECARBONISATIONREQUIRESAWHOLELIFE-CYCLEAPPROACH2.1EmbodiedversusOperationalCarbonEmissionsinBuildings72.2EmbodiedEmissionsfromExtractingandProducingBuildingMaterials92.3EmbodiedEmissions:FromEnd-of-LifetoRe-UseandRecycling102.4ImplementingaWholeLife-CycleApproachtoBuildingMaterials112.5TheWholeLife-CycleApproach:PathwaysforDecision-Makers122.6StrategiesTowardsaBuildingMaterialsRevolution:“Avoid-Shift-Improve”143AVOIDWASTE,BUILD(WITH)LESSANDIMPROVECIRCULARITY3.1CircularDesignToolsandStrategiesforPlanningandDecision-Making173.2UpstreamDesignChoicesAreKeytoTacklingCarbonEarly173.3BuildingLessbyPrioritizingRenovationandUseofExistingBuildings183.4FocusingonEnd-of-Use,NotEnd-of-Life,toAvoidLandfill193.5DesignforDisassemblyandModularConstruction213.6(Re-)UseofSecondaryMaterials213.7RecyclingOnlyasaLastResort243.8CircularStrategiesinNewConstructiontoAvoidEmbodiedEmissions244SHIFTTOBIO-BASEDBUILDINGMATERIALS4.1ScalingRenewableBuildingMaterials:OpportunitiesandChallenges274.2TimberandWood284.3Bamboo344.3Biomass36CONTENTSivBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE5IMPROVECONVENTIONALBUILDINGMATERIALSANDPROCESSES5.1DecarbonizingConventionalBuildingMaterials415.2ConcreteandCement425.3Steel495.4Aluminium515.5PlasticsandPolymerComposites545.6Glass575.7MasonryandEarth-BasedMaterials606TOOLSFORASSESSINGCARBONIMPACTSACROSSTHEBUILDINGLIFECYCLE6.1MeasurementandDataAreImproving,ButTransparencyandVerificationAreNeeded656.2ExistingToolsforAssessingCarbonImpact656.3RecommendationsforFutureCarbonAssessmentTools676.4ToolsforGreenhouseGasAssessmentAreNeededforDistrict-ScalePlanning696.5GlobalStandardsandLabelsforEmissionTransparencyCanGalvanizetheMarket716.6ChallengesandNextSteps737POLICYRECOMMENDATIONSFORDECARBONIZINGMATERIALSINTHEGLOBALBUILDINGSECTOR7.1SetTheVision,LeadbyExampleandImproveMultilevelGovernance767.2MakeCarbonVisibleThroughImprovedDataAccessandQuality787.3Adaptnormsandstandardstoallowfortheuseofalternativeorlower-carbonbuildingmaterialsandconstructionpractices797.4Acceleratetheindustrytransition807.5Ensureajusttransition827.6Strengtheninternationalactionandcollaborationforcollectiveimpact848CONCLUSIONANDDISCUSSION86Bibliography92Annexes102Annexes1.Construction,RenovationandDemolitionWasteAnnexes2.“Re-inventing”CementIsCriticalAnnexes3.MaterialsFlowsforSteel,AluminiumandGlassAnnexes4.CountryCaseStudiesofthe“Avoid-Shift-Improve”StrategiesvBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREABBREVIATIONS°CDegreesCelsiusASEANAssociationofSoutheastAsianNationsBPIEBuildingsPerformanceInstituteEuropeBREEAMBuildingResearchEstablishmentEnvironmentalAssessmentMethodologyCCSCarboncaptureandstorageCO2CarbondioxideEJExajouleEPDEnvironmentalProductDeclarationEUEuropeanUnionG7GroupofSevenGDPGrossdomesticproductGlobalABCGlobalAllianceforBuildingsandConstructionGtGigatonHFCHydrofluorocarbonIEAInternationalEnergyAgencyISOInternationalOrganizationforStandardizationkWKilowatt-hourLEEDLeadershipinEnergyandEnvironmentalDesignm2SquaremetreNDCNationallyDeterminedContributionOECDOrganisationforEconomicCo-OperationandDevelopmentPEEBProgrammeforEnergyEfficiencyInBuildingsPVPhotovoltaicSDGSustainableDevelopmentGoalSDSSustainableDevelopmentScenarioTWhTerawatt-hourUNUnitedNationsUNEPUnitedNationsEnvironmentProgrammeUNFCCCUnitedNationsFrameworkConventiononClimateChangeWWattKEYTERMSBuildingsandconstruction:Alloftheactivitiesthatencompassthemakingofbuildings,includingtheconstructionofbothresidentialandcommercialbuildings.Thefiveprimarysectorsoftheconstructionindustryareresidential,commercial,heavycivil,industrialandenvironmentalconstruction.Builtenvironmentsector:Alloftheactivitiesthatencompassthemakingofenvironmentsforhumanoccupantsandactivities,includingtheconstructionofhomes,commercialbuildings,streets,highways,infrastructureandzoning.Builtenvironmentprocess:Alloftheactivities,processes,anddecisionsthatencompassthemakingofenvironmentsforhumanoccupantsandactivities,acrossthelifecycleofbuildingprojectsfromextractiontodesignconstructionandendoflife,includingtheconstructionofhomes,commercialbuildings,streets,highways,infrastructureandzoning.Carbondioxideequivalent:Anequalgreen-housegasemissionsquantitythatrepresentsthenumberofmetrictonsof(CO2)emissionswiththeequivalentglobalwarmingpotentialasanothergreenhousegas.Itiscommonlyused,sinceitistheprimarycomponentingreenhousegasemissionsthatresultfromtheuseoffossil-basedenergyandemissionsfrombiologicalmaterials,wasteandchemicalreactions.Carboncaptureandstorage:Inthecontextofbuildingsandconstruction,carboncapturereferstoactiveprocessesofremovingcarbonfromtheatmospherethroughprocessessuchasplantphotosynthesisandcarbonationincementitiousmaterials.Carbonstoragereferstohowcarboniskeptwithinthebuildingmaterialitselfovertime.Carbonloophole:Thegreenhousegasloopholethatiscreatedbyglobaltrade,wherebyproductionofmaterialsarerelocatedandemissionsallocatedtocontextswithlowerproductioncostsandhistoricemissionpatterns.Carbonoffsets:Instrumentsthatallowcompaniestodemonstratenetzerogreenhousegasemissionsbypayingforanactivityoutsideofitsorganizationthatverifiablyreducesgreenhousegasemissions.TheyaremeasuredinunitsofonemetrictonofCO2-equivalentemissions,andtheyhavean“additionality”requirement,whichmeansthattheymustcomefromaprocessthatisverifiedtobe“additional”towhatwouldhappenundertypical“business-as-usual”scenarios.Circulareconomy:Aneconomythatusesasystems-basedapproachinordertomaintainthelifespanand/orcirculationofmaterials,products,andservicesforaslongaspossible.“Circularity”isacommontermthatreferstoproductionprocessesandeconomicmodelsthatarerestorativeandregenerative,enablingresourcestomaintaintheirhighestvalue,firstlyby“avoiding”theirextractioninthefirstplacethrough“improving”designprocessestoeliminatewasteandmaterialoverconsumption,andsecondlyby“shifting”torenewableandrecycledmaterials(U.S.EnvironmentalProtectionAgency2023).DesignforFreedom:AmovementandinitiativebyGraceFarmstocreatearadicalparadigmshiftwithinthebuiltenvironmenttowardsethicallysourced,forcedlabour-freematerials.Embodiedcarbon:AtermcommonlyusedinthebuiltenvironmentindustriestodenotetheamountofCO2thatisemittedasaresultofalltheenergythatgoesintoamaterial’sproduction(extraction,manufacture)construction,maintenance,refurbishmentandend-of-use(demolition,incineration,landfill,etc.)acrossthelifecycleofthebuiltenvironmentprocess.Environmentalproductdeclaration(EPD):Adocumentthatismeanttotransparentlycommunicatetheenvironmentalperformance/impactofaproductormaterialacrossitslifecycle.Forcedlabour:Allworkorservicethatisextractedfromanypersonunderthethreatofapenaltyandforwhichthepersonhasnotofferedthemselfvoluntarily.GreenhouseGas(GHG)Protocol:AframeworkestablishedbytheWorldResourcesInstituteandtheWorldBusinessCouncilforSustainableDevelopmenttoassiststakeholdersacrossthebuiltenvironmentprocesssuchasgovernments,businesses,industryassociations,non-go-vernmentalorganizationsandotherentities,toidentify,measure,manageandreportthegreenhousegasemissionsthatresultfromtheiractivities,accordingtostandardguidelines.Life-cycleassessment:Aprocedurefortabulatingandreportingtheenvironmentalimpactofamaterial,productorserviceoveritslifetime.Thelife-cycleassessmentprocessincludesthefollowingprocedures:1)goalandscopedefinition,2)inventoryanalysis,3)impactassessmentand4)interpretation.Operationalcarbon:Emissionsgeneratedthroughthefunctionandmaintenanceofthebuilding.Scope1,2and3emissions:TheGHGProtocolclassifiesgreenhousegasemissionsintothreedifferentscopes:Scope1emissionsaredirectemissionsthatoccurfromasourcethatcanbecontrolledbyanorganization.Scope2emissionsrefertoindirectemissionsthatresultfromthegenerationofpurchasedenergy.Scope3emissionsareindirectemissionsthatoccurinthevaluechainofthereportingentity(company,municipality,community,etc.)includingbothupstreamanddownstreamemissions,butthatarenotinthecontrolofthereportingentity.Wholelife-cycleassessment:Amethodthatquantifiesthecarbonimpactofamaterialorprocessacrosstheentirebuildinglifecycle,fromembodiedtooperationalcarbonandendofuse.Wholelife-cycleassessmentrequiresrigorousstandardisedmethodologysothatthescopeandbenchmarksofassessmentscanbetransparentlycommunicatedandevaluated.viBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREFIGURES1.1Globalcarbonemissionsfromthebuiltenvironmentsector,bysource,2021P.11.2Globalmaterialflows,bytype,1945versus2015P.32.1EmbodiedandoperationalcarbonemissionsP.72.2ProjectedcontributionsfromembodiedandoperationalcarbonwithinthebuildingsectorP.72.3EmbodiedandoperationalcarbonemissionsoverthebuildinglifespanP.82.4ImpactofmaterialselectiononurbansurfacetemperaturesandtheurbanheatislandeffectP.92.5Projectedgreenhousegasemissionsfrombuildingmaterialsinabusiness-as-usualscenarioto206020P.102.6Scope1,2,and3carbonaccountingforamaterialproductP.112.7CarbonimpactsofmaterialsacrossthewholebuildinglifecycleP.122.8KeystakeholderswhoseparticipationiscriticaltothedecarbonisationofbuildingsatdifferentlifephasesP.132.9Decarbonizingbuildingsandconstruc-tionthroughtheAvoid-Shift-ImproveapproachP.142.10Transitioningbuildingmaterialstoalow-carbonfutureP.153.1OpportunitiestoreducecarbonateachphaseofthebuildinglifecycleP.173.2OpportunitiestoreducecarbonineachstageofprojectdevelopmentP.183.3RepresentativehousinginLimaandMontréalandtypicalmaterialsused,bymassandvolume,2019P.213.4Carbonimpactsofdifferentend-of-usestrategiesinLimaandMontréalP.224.1HistoricaldevelopmentofatmosphericcarbonpatternsP.274.2Globaltrendsinharvestedwoodproducts,1960-2018P.294.3Embodiedcarbonbalanceofcross-la-minatedtimberandforestbyproductsP.324.4CarbonemissionsandstorageforlaminatedbambooversusotherbuildingmaterialsP.354.5Comparisonoflife-cyclecarbondioxideemissionspersquaremetreforfourwallassemblytypesP.374.6Examplesofgreenbuildingenvelopesusinglivingbiomassandotherclimate-friendlyfeaturesP.384.7RelationshipbetweenembodiedandoperationalcarbonwithinlivingbiomassmaterialsystemsP.395.1Sharesoftotalgreenhousegasemissions,byindustrialsector(left)andmaterialclass(right)P.415.2Totalin-usecementstocks,byregion,1931-2014P.435.3DominanceofconcreteandcementintheembodiedemissionsofnewlyconstructedbuildingsP.435.4Evolutionarystagesofpercapitain-usecementstocks,bycountryP.445.5Potentialforregionstoleapfrogtowardsmorewealthandlesscarbon-intensivecementP.445.6Thewhole-systemspathwayresultsinemissionreductionthroughmoreefficientuseofcementandconcreteP.455.7Creationofhollow-coreconcreteslabsatBotswanaInnovationHubP.485.8ThetimedelayintherecyclingofmetalsP.505.9Globalaluminiumproduction(2000-2030)andembodiedenergy,bysourceP.535.10Sharesofprimaryandrecycledaluminiumsince1950,andprojectionsthrough2050P.535.11Totalplasticsproductionbyregion,1980-2060P.545.12EndusesofpolymersforthebuildingsandconstructionindustryP.555.13Life-cyclegreenhousegasemissionsfromtheplasticssector,2015P.565.14AdvancedglassfaçadesP.595.15Climatetypesandthepotentialforearth-basedbuildingsP.615.16ComparisonofthecarbonintensityandmechanicalperformanceofdifferentstabilisedearthmasonrytechnologiesP.615.17Compressedearthblockmasonrywallandon-sitemanufacturinginDakar,SenegalP.626.1MunicipalbuildingenergycodesneedtotransitiontoincludeembodiedenergyP.656.2TheClark’sCrow“ataglance”datatoolP.696.3Greenhousegasemissionspertotalfloorareafor19detailedplansassessedinHelsinki(50-yearassessmentperiod)P.707.1HumansarePartofaLivingEcoysteym:FrameworkforDignityacrossthebuiltenvironmentlifecycleP.85A.1Shareofconstruction,renovationanddemolitionwastesenttolandfillinselectedcountriesP.102A.2EmergingalternativecementitiousbindersP.103A.3Availabilityofalternativecementitiousbinders,byregionandtype,2018P.104A.4SteelmaterialflowsP.105A.5Globalflowsofaluminium,2007P.106A.6GlobalmaterialflowandendusesofglassP.106TABLES1.1Categorizationofbuildingsworldwidebasedondurabilityandotherfactors5.1SummaryofDecarbonisationStrategiesperMaterial6.1Commontoolsandstandardsusedtoassesslife-cycleemissions6.2Emergingmechanismstosupportwholelife-cycledecarbonisationofbuildingmaterials8.1Whodoeswhattodecarbonisematerials?BOXES1.1Theneedtoaddressthefullrangeofbuildingtypesgloballyindecarbonisa-tionefforts2.1Transitioningbuildingmaterialstoalow-carbonfuture3.1LimaandMontréal:Understandingthedecarbonisationpotentialofcircularend-of-usestrategies4.1Groundinggenderequityasadriverwithincirculareconomies4.2TakingpressureoffWestAfrica’stropicalforeststhroughtheuseofnon-timberbiomassresources4.3Thebenefitsofintegratinglivingbiomasssystemsinbuildings5.1On-sitepre-fabricationofmodularconcretecomponentsinBotswana5.2Emergingresearchonstoringcarbondioxideinconcrete5.3GreeningthemasonryvaluechaininWestAfrica6.1DataHomebase:AwebapplicationvisualizingCanada’shousingcharacte-risticstofosteracirculareconomy6.2Finland’s“At-a-glance”AVAtoolforgreenhousegasassessmentattheneighbourhoodlevel6.3NetzeroconstructionatLendleaseAmericas7.1GlobalABCRoadmapsforBuildingsandConstructionviiBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREBUILDINGMATERIALSANDTHECLIMATEExecutiveSummaryBuildingMaterialsAreSettoDominateClimateChangeUrbanisationisrisingandpolicyactionisurgentlyneededtoshiftbuildingmateriallifecyclestowardsregenerativemethods.Thebuiltenvironmentsectorisbyfarthelargestemitterofgreenhousegases,responsibleforatleast37percentoftheglobalemissions.Yetithasreceivedonlyasmallfractionofclimate-focuseddevelopmentfunding,comparedtoothersectors.Untilnow,mostoftheprogressinthesectorhasbeenmadeonreducingthe“operationalcarbon”ofabuilding–theemissionscreatedfromheating,coolingandlighting,whichareprojectedtodecreasefrom75percentto50percentofthesectorinthenextfewdecades.However,solutionsforreducingthe“embodied”carbonemissionsfromthedesign,productionanddeploymentofbuildingmaterialssuchascement,steel,andaluminiumhavelaggedfarbehind.Thereasonsforthisarecomplexandmanyactorsareinvolved.Therefore,theincentivesfordecarbonisationneedtosimultaneouslyenabledecisionmakers,fromproducerstoconsumersacrosstheglobalmaterialsupplychains,inbothinformalandformalbuildingsectors.Thisreporthighlightstheurgentneedtodevelopnewmodelsforcooperationonthedecarbonisationofbuildingmaterials,iftheworldistoreachitsgoalsfornetzeroemissionsfromthebuiltenvironmentsectorbythemid-century.Thereportfocusesonthreeurgentpathwaysthatmustbefacilitatedbysupportingstakeholdersacrossthelifecycleofthebuiltenvironmentsectorinordertodecarbonise:AVOIDtheextractionandproductionofrawmate-rialsbygalvanisingacirculareconomy,whichrequiresbuildingwithlessmaterialsthroughbetterdata-drivendesign,whilereusingbuildingsandrecycledmaterialswhereverfeasible.SHIFTtoregenerativematerialpracticeswhereverpossiblebyusingethically-producedlowcarbonearth-andbio-basedbuildingmaterials(suchassustainablysourcedbricks,timber,bamboo,agriculturalandforestdetritus)wheneverpossible.IMPROVEmethodstoradicallydecarboniseconventionalmaterialssuchasconcrete,steelandaluminium,andonlyusethesenon-renewable,carbon-intensive,extrac-tivematerialswhenabsolutelynecessary.©SwinertonixBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREReducingembodiedcarboninbuildingmaterialstonetzeroisachievableby2060,ifwepromotethedevelopmentanduseofbestavailabletechnologiesfordecarbonisingconven-tionalmaterials,combinedwithamajorpushtoadvancetheincreaseduseofregenerative,circularbiomaterialsfromforestandagriculturestreams.Oneofthemostimportantopportunitiesforsynergisticpotentialtodecarbonisethesectorlieswiththeabilitytolinktheproductionofbuildingmaterialswiththemanagementofcarboncyclesofforestsandagriculturallands.Thiswouldproducecompoundingbenefits,fromreducingtheriskofforestfires,toincreasingtheproductivityofforestedandagriculturallandtracksthroughrejuvenationandresponsiblereforestation.Increasedinvestmentisneededtoredirectglobalbiomassresiduesintocostcompetitiveconstructionproductssuchascementitiousbinders,bricks,panelsandstructuralcomponents.Compoun-dingbenefitsincludethecapacitytostorecarbonwithinbuil-dingmaterialsandproducts,therebyreducingclimatechangeemissionsfromdecayingmatter,forestfiresandtheburningofcropwaste.Further,majorcarbonsequestrationbenefitscouldcomefromnewcooperativeapproachesbetweenbuildersandforestmanagerstoincreasethebiodiversityofforeststhroughtheselectionoffunctionalattributesforbuildingmaterialsaccordingtospecies.Policiestosupportmaterialproducersandusersacrossthebuildinglifecyclerangefromland-usemanagementtocarboncertifications.However,theeffectsofmaterialselectiononecosystemsneedtobebetterincorporatedintoassessments.Globalco-operationiscriticaltowardsensuringajusttransi-tiontoethicaldecarbonisation.Stakeholdersinthebuildingprocessmusthaveaccesstoreliabledataontheprovenanceofmaterialstoensurethatcarbontaxesandotherregulationsarenotgreenwashingmaterialproductsthathavebeenmadewithunfairlabour,oraredetrimentaltolocalbiodiversityandthelifequalityandexpectancyofregionalpopulations.Acrossdifferentregionsandclimates,methodswillvaryinimplementingthethreemaindecarbonisationprinciplesdiscussedinthisreport:“Avoiding”emissionsthroughcircu-larity,“Shifting”tosustainablematerials,and“Improving”theproductionofextractivematerials.Patternsinglobalmaterialflowscenariospointtowardstwokeydifferences:indeve-lopedcountries,thefocuswillbeonrenovationoftheexistingandageingbuildingstock,whereasindevelopingcountries,theneedfornewconstructionisevidentinthefaceofrapidurbanisation.©denis-lorain/unsplashINACIRCULARECONOMYBUILDINGSWILLBECOMEMATERIALBANKSFORFUTURECONSTRUCTIONxBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE1.AVOIDWaste,Build(with)LessandImproveCircularityThereareopportunitiesforcirculardesign,recyclingandre-useateachphaseofthebuildinglifecycle.Thepotentialtoreduceandavoidembodiedcarbonisgreatestduringtheplanninganddesignphases,reinforcingtheimpor-tanceoftakingawholebuildinglife-cycleapproachincirculareconomydesign.Inacirculareconomy,wherewasteiseliminated,extendingabuilding’slifeisthemostvaluableandleast-wastefuloption–withrenovationgenerating50-75percentfeweremissionsthannewconstruction.Newconstruc-tioncanincorporatecirculardesignstrategies–promoting“designfordisassembly”–thatresultinatleast10-50percentdecreaseingreenhousegasemissions.Earlydesignchoicesgreatlyimpacttheabilitytoreuseorrecyclematerialslaterinthebuildingcycle.Transitioningtoacirculareconomyisoneoftheessentialpathstowardsreducingcarbonemissionsinbuildings.Criti-cally,itrequiresrethinkinghowbuildingsaredesigned.Designdecision-makingduringeachphaseofabuilding’slifecycleoffersopportunitiestoreduceembodiedcarbon.Informalconstructionsectorstendtoalreadyexcelatacircularityandreuse,howeverinformalsectors,keycirculareconomydesignstrategiesincludecomputer-aideddesignoptimisa-tionforlessmaterialusage,selectingmaterialsthatreducenon-renewablematerialextraction,designingformaterialandcomponentreuse,andextendingthelifeofbuildingsand/ormaterialsthroughpropermaintenance.Despitegrowingawareness,mostcontemporarymaterialcyclescontinuetobemorelinearthancircular.Asaresult,non-renewable,energy-intensivematerialsstillsupplythemajorityofdemand.Sofar,recycledmaterialsarenotavailableinsufficientquantitiesandqualities,andthegapbetweensupplyanddemandforrecyclablesisgrowinginmostsectors.Anewsupply-and-demandmodelisneeded,withnewenterprisesthatallowforthecarefuldismantlingofbuildingsandforthestoring,preparationandmaintenanceofsecond-cyclematerialsforresalethatwillenablecirculareconomieswhileprovidingjobopportunities.Facilitatingaccesstoreliableinformationandverificationiskey.Decision-makersmustsupporteffortsbystakeholdersacrossthebuildingindustryastheyseektodecarbonisematerials.Thecurrentfragmentationoftheindustryisunder-miningdecarbonisationefforts–withinsufficientcoopera-tionamongmanufacturers,architects,engineers,buildersandrecyclers.Effortsbyindividualstakeholderstoimprovedecarbonisationoutcomeswillnotsucceedunlesstheyaresupportedbypolicyandfinanceacrossthedifferentphasesofthebuildingprocess.Forexample,effortsbydesignersandcommunitiestousemorerecycledmaterialsareoftenstymiedbythegrowinggapbetweensupplyanddemand.Yetthisgapcannotbeclosedwithouttheadoptionofbuildingcodesthatrequiredesignerstospecify“circular”componentsmadewithre-usable,renewablematerials.Evensmallimprovementstosynergisticallysupportbothproducersandusersthroughpolicyandfinancewouldbepreferabletoisolatedactions.AvoidNewExtractionbyEnablingaCircularMaterialEconomyThatPrioritisesReuseandRecyclingIndevelopedeconomies,itiscriticaltoimproveindustrymethodsacrossstakeholders,fromdesigners,tocommuni-tiesandtocommittorepurposingthemassivequantitiesoffailingreinforcedconcretefrom20th-centuryinfrastructurethatisnearingtheendofitsfirstlife,sothatitcanbetrans-formedintomaterial“banks”fornewconstructiontoslowthepaceofnon-renewablematerialextraction.Todoso,farmoreinvestmentisrequiredforresearchanddevelopmentofdesignandsecondarymanufacturingmethodswithequipmenttorecoverandprocessconstruction,renovationanddemolitionmaterials.Governmentincentives,awarenesscampaigns,andlegalandregulatoryframeworkshaveshowntobeeffectivetoincentiviseapproachesforre-useandrecycling.Recyclingsystemsforbuildingmaterialstendtorequiresimilarkindsofsupportacrosscountries,includingpromotingmarketsforre-usableproducts,providingincentivesforthecreationofre-usecentresanddevelopingspecialisedcontractors.Duetotheinterdependentnatureofthebuiltenvironmentsector,inwhichmanymaterialsmaybeusedacrossbuildingsystemsandtypes,farmoreinvestmentisrequiredformeasuresthatensurecooperationacrosssectorsandborders.THREEPRINCIPLESFORENACTINGMATERIALDECARBONISATIONxiBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE2.SHIFTtoBio-BasedBuildingMaterialsInnovatingbeyondbusiness-as-usualforestry:materialsthataretrulyrenewablerequireregenerativeapproachestoresourcemanagementthatincentivizebiodiversity.Inpursuingthesecondpathwaytodecarbonisation,therearetransformativeopportunitiestodevelopecologicallysoundmethodsformanagingthecarboncycleofregionalforestsandagriculturallands,withimportantco-benefitstoconsider,aswellasrisks.Bio-basedmaterialsmayrepresentourbesthopeforradicaldecarbonisationthroughtheresponsiblemanagementofcarboncycles.Theshifttowardsproperlymanagedbio-basedmaterialscouldleadtocompoundedemissionsavingsinthesectorofupto40percentby2060inmanyregions,evenwhencomparedtosavingsfromlow-carbonconcreteandsteel.However,envisioningandimplementingalarge-scaletransi-tiontocircularandbio-basedmaterialsinthebuiltenviron-mentcarriessubstantialrisksifthechangestothebroaderecological,socialandeconomiccontextarenotplannedforandhandledverycarefully.Decarbonisationofbuildingscreatesrisksofunintendedconsequencestotheecosys-temsthatunderpintheproductiontosupplythealternativebio-basedmaterials.Itcanalsoleadtotheperpetuationorexacerbationofunjustlabourpractices,andtoinequitableshiftsineconomicgainsandlossesasindustriestransition.Renewable,bio-basedbuildingmaterialshaveauniquecapacitytodrivereductionsinatmosphericcarbon,iftheyaresustainablysourcedandmanaged.Currently,woodistheleadingscalablebiomaterial,andpatternsoftimberproductionanduseofferbothopportunitiesandchallenges.Therisingdemandfortimbercouldacceleratemarketsforupcyclingby-productsfromforestsandagriculture,addingthemassivepotentialbenefitsofreducingforestfiresandgreatlyexpandingthecarbonsequestrationpotentialofbothforestsandurbanareasbyupto70percentincertainregions.However,akeyprerequisiteisthatintersectoralapproachestorenewableresourceandlandmanagementareurgentlyrequiredtotransitionawayfromthehighcarbonimpactsofmuch“business-as-usual”forestryandagriculture.Keyrecommendationsforbio-basedmaterialsincludestandardisationofperformance,integrationintobuildingcodes,broadindustryupskilling,marketingandfinancialincentivisation,andregulatedcooperationinsustainableland-usetechniques:1.MandatetheUseofLivingSystemsandBiomasstoProtectUrbanClimatesPerhapsthemostimpactfulpolicyforchangingtheimpactofurbanmaterialsonclimatechangeistomandatetheuseofvegetatedsurfacestocoverapercentageofexposedShutoMorioka/EyeEmCollectionviaGettyImagesNEWCOOPERATIVEMODELSBETWEENTHEBUILDING,FORESTRY,ANDAGRICULTURALINDUSTRIESCOULDLEADTOAREVOLUTIONINTHECARBONCYCLEMANAGEMENTOFREGIONALECOYSTEMSxiiBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREconcreteorasphalt,whereverpossible.Thishasthecombinedimpactofnaturallykeepingbuildingscool,reducingenergyconsumption,aswellasabsorbingstormwatertoreduceflooding,replenishwatertablesandurbanbiodiversity.2.PromotetheTransitiontoLow-CarbonMaterialsDecarbonisationofthecementsectorandothermajoremit-tersisbeingenhancedbyreplacingtraditionalmethodswithhybridbio-basedmaterialsandotherlow-carbonmaterials.However,theseemergingmethodsarenotyetcostcompeti-tive,andwidespreadbiasesremainthatprotectentrenchedmethods.Thus,scalinguprequiressubstantialinvestmentinresearchanddevelopmentofbothmajorandemergingprodu-cers,alongsideincentivesand/orenforceablebuildingcodes.3.ShiftPublicPerceptionsregardingTraditionalVernacularMaterialsWhyhasitbeensodifficulttodecarbonisebuildingmaterials,andwhatcanbedoneaboutit?Peoplehavenotalwaysbuiltwithcarbon-intensivematerialsandtheirfutureuseisnotinevitable.Beforethemiddleofthe20thcentury,thevastmajorityofculturesbuiltlargebuildingsandcitiesoutofindigenousearthen,stoneandbio-basedmaterials–suchastimber,cane,thatchandbamboo.However,duringthelastcentury,withevergreateraccesstofossilfuels,theglobalextractionandproductionofcarbon-intensive,mineral-basedmaterials(suchasconcreteandsteel)explodedandbecamewidelyassociatedwiththeimageofmodernprogress,strengthandexpediency.Yetmanycontemporarybuildingstructuresandmaterialsonlygivetheillusionofdurability,astheywere“designedforobsolescence”.Buildingassemblieswithlimitedlifespansarenowdestinedforlandfillsatdemolition,astheyhavebeenprocuredthroughcomplexsupplychainsandarenotdesignedforeasydisassemblyorre-use.Anexampleisthevastnumberoffailingconcretestructureswithsteelandglassfaçadesacrossthedevelopedworldthatneedtobereplacedjustafewdecadesaftertheywerebuilt.Meanwhile,stone,woodandevenmassivemudbuildingshavebeenmaintainedforcenturieswiththeirstructuresintact.Thisreportoutlineskeypoliciesandtoolsthatcanbeadoptedbymultiplestakeholdersatdifferentphasesofthebuildingprocessthatlookbeyondoperationalenergyandthatfaci-litatetheradicalaccelerationofbuildingdecarbonisation,whilealsobolsteringthehealthofbothhumanpopulationsandbiodiverseecosystems.4.HarnessingtechnologytoimprovematerialswhilerecapturingtheintelligenceofthepastContemporarymaterialsdonotinherentlylackdurability.However,itispossibletoachievemuchbetterperformancefromcontemporarymaterialsandbuildingsbyharnessingdataandtechnologytorevolutionisethemeansandmethodsofdesignandconstruction.Toreachnetzeroemissionsinthebuiltenvironmentsector,thebuildingmaterialsofthefuturewillneedtobeprocuredfromrenewableorreusablesustai-nablesourceswhereverpossible.Ifrawmaterialextractionmusttakeplace,thendramaticallyimprovedmethodsfordecarbonisationmustbeimplementedbytransitioningtorenewableelectrificationofallprocesses,andcomplementedbycarboncaptureandstoragemethodsthatrequiresubs-tantialsupportforresearchanddevelopmentinordertodemonstratescalability.TimberandWoodFuturescaleupoftimberrequirescarefulmanagementofthecarboncycleofforestsandagriculturallandsinordertoincreasetheirnetproductivityforbothcarbonsequestration,foodandmaterialproduction.Thebuiltenvironmentuses38percentoftheworld’swoodproducts.Increasingly,masstimberisbecominganattrac-tivealternativetocarbon-intensiveconcreteandsteelduetoitspotentialforscalability,sustainability,strengthandflexibilityinmid-riseurbanbuildings.Advancesintimberbuildingmaterialtechnologiesaremakingitpossibletoshifttowardslarge-scalestructuraltimberproducts,providedthatthetimberindustriescontinuetoinnovateandareregulatedforsustainablepractices.Ensuringthatthevastmajorityoftimberissourcedfromsustainableforestrywillbecrucialformakingthisatrulysustainabletransition,avoidingpitfallssuchaslaxregulations,particularlyinemergingeconomies.Itiscriticaltoprioritisethedevelopmentofafforestationpractices,particularlyinnaturalforestsoftropicalcountries,whereloggingratesfaroutpaceeffectivereplanting.“Circulartimber”includestheincreaseduseofforestby-products.Bothclear-cuts(decayinglogsandresiduesfromlogging)andoff-cutsfromwoodmanufacturinghavepotentialforrecons-titutedwoodproducts.BambooScalingfast-growingbambooshowsmajorpromisebutrequiresinnovationincarbon-neutralbinders.Bambooisafast-growingrenewableresourcethathaswitnessedsignificantadvancesasascalablebuildingmaterialinthelasttwodecades.Progressinengineeredbamboohasdemonstratedstructuralperformancesimilartothatofcross-laminatedtimberandsteel.However,thevariabilityinspeciesacrossregionsrequiresinvestmentsinfurtherdeve-lopmentoflow-costandlow-carbonconstructionmethods,standardsandcertificationstogaintheconfidenceofindustryforlarge-scaleapplications.Aswithallengineeredbio-basedmaterials,incentivesurgentlyneedtoprioritiseprogressin“greenchemistry”todevelopnon-toxicbindersandglues.Aswithtimber,thesustainablescalingofthesupplyofbambooiscritical,withregulationsinplacethatavoidclear-cuttingofforestswhilegainingaccesstoland,andalsoensuretranspa-rencyofsustainablepracticesthroughoutthesupplychain.xiiiBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREBiomassTherecuperationofby-productsfromforestryandagriculturehassynergisticbenefitsofreducingforestfiresandcropburning.Non-timberlignocellulosicmaterialsgeneratedfromforestry,agricultureandbiomassresiduesrepresentanuntappedbutpotentiallymassivelocalsupplychainforbuildingmaterials,fromsourcesthatcurrentlygotowasteandcontributesubs-tantiallytogreenhousegasemissionsthatalsoaffectair,landandwaterqualityacrossregions.However,majorinvestmentsarerequired.Ifscaleduptoreducetheuseofpetrochemicaland/ortimber-basedbuildingmaterials,fast-growingligno-cellulosicmaterialscouldsignificantlylowertheprojectedpeakinglobalcarbondioxideemissions.Whatisawholelife-cycleapproach,andwhyisitcriticalfordecarbonisationofthesector?Thereportemphasisestheneedtotakeawhole-lifecycleapproachwhenassessingstrategiestodecarboniseemis-sionsfromthebuiltenvironment.Awholelife-cycleapproachisradicallydifferentfromalinearapproachasitincorporatestheprinciplesofacirculareconomy.Itrequiresconsiderationoftheenvironmentalimpactsofmaterialchoicesbeforethematerialsareevenextracted,andthenagainateachphaseofthebuildinglifecycle,fromextractiontoprocessing,installa-tion,useanddemolition.Thismeansthinkingabouthowthechoiceofmaterialsimpactseverythingfromthefunctioningofregionalecosystems,humanhealthandwellbeing,totheamountofheatingorcoolingneeded–andhow,attheendoftheiruse,thesematerialscanprovidea“bank”ofresourcestothenbere-used.Whentakingsuchanapproach,theworkofthegeo-biospheretoproducespecificlocalnaturalresourcesisvaluedasarenewableresource.Therefore,theuseofbio-basedandrenewablematerialssuchastimber,bambooandbiomassproductsmustbesupportedwithregulationstoprotecttheecosystemsthatsustainthoseresources,withcarefulconsi-derationofregionallyspecific,sustainablelanduseandforestmanagement.Wholelife-cyclethinkingrequiressensitivitytothecontext–tolocalculturesandclimates.Ashifttolowcarbonearth-andbio-basedbuildingmaterialsisoftentechnologicallypossiblebutsociallydifficulttoimplement,asmanyculturesconsiderconcreteandsteeltobe“modern”materialsofchoice.Yetthereisgreatpotentialtoshifttolow-carbonmaterialsduetoadvancesinengineeredtimber,bambooandbiomassassubstitutesforsteelandconcrete.3.IMPROVENon-RenewableBuildingMaterialsandProcessesSupplyofreusedandrecycledmaterialswillneedtocatchupwithgrowingdemand.Formaterialproducers,someofthehighest-prioritypathwaystodecarbonisearebyimprovingtheprocessingofconventionalmaterialssuchasconcrete,steel,aluminium,plastics,glassandbricks.Keytoalleffortswillbeelectrifyinganddecarbonisingtheenergythatisusedtoproduceandmaintainmaterials,buildingsandurbaninfrastructureacrosstheirlifecycle.Mostmaterialeconomiescontinuetobepredominantlylinear,ratherthancircular.Asaresult,virginandnon-renewablematerials,thatareenergy-intensivetoproduce,stillprovidethemajorityoftoday’smaterialdemand,whilerecyclablesarenotavailableinsufficientquantitiesandqualities.Reducingrawmaterialextractionandharvestingthroughrecyclingandre-usemayalsomitigatesocialillssuchasforcedlabourupstreaminthesupplychain.FacilitatetheDecarbonisationofConventionalNon-RenewableMaterialsCement,steelandaluminiumarethethreelargestsourcesofembodiedcarboninthebuildingsector.Thelowesthangingfruitistofacilitateand/ormandatetheadoptionbyindustryaswellasenergyinfrastructureplannersofalreadydevelopedbestavailabletechnologiesfordecarbonisation,andtomaxi-misetheuseofcleanenergyinmanufacturingprocesses.Cement/ConcreteCementcanbedecarbonisedbyreducingtheclin-ker-to-cementratio,increasingtheshareofcementalternatives,shiftingtoelectrickilnspoweredbyadecarbonisedelectricgridsuppliedwithrenewableenergy,whilepotentiallystrengtheningconcretethroughcarboncaptureandutilisationduringmanu-facturing.Concreteisthemost-usedmaterialinthebuildingsector,andtheprocessingofcement,thebindingagentinconcrete,contributes7percentofglobalcarbonemissions.Becauseconcretehasadevelopedsupplychainandinfrastructure,itdominatestheindustryevenwhereotherlower-carbonmaterialscouldsuffice.Concreteusehasgrown10-foldinthepast65years,comparedwitha3-foldincreaseinsteelandnear-stagnantgrowthintimber.Currently,lessthan1percentofconcreteismadefromrecycledmaterials,soincentivizingtheproductionoffactory-producedmodularconcretethatisdesignedforre-useshouldbeprioritised.xivBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREAsmuchas25percentofemissionsfromcementandconcretecanbereadilysavedbyadaptingbuildingcodesandbyeducatingarchitects,engineersandbuilderstousethebestavailabletechnologies.Substitutingcementandconcretewithbio-basedand/orearth-basedbuildingmaterialsisalsokey.Thehighestprioritiesfordecarbonizingcementproductionare:reducingtheclinker-to-cementratio;electrifyingproductionwithrenewableenergysources;scalinginnovativebutnascenttechnologies(carboncaptureandstorage,bindersmadefromalternativematerials);andincreasing(ormandating)pre-fabricationofcircularunitsthatcanbedisassembledandre-usedforfuturebuilding.SteelInprimarysteelproduction,ashiftfromblastfurnacetodirectreducedirontechnology,coupledwithelectricarcfurnacespoweredbyrenewableenergysources,offersthegreatestemissionreductionpotential,togetherwithincreasingrecyclingefficien-ciesandcarboncaptureandstorage.Steelisthesecondmostabundantmaterialusedinbuildings,andembodiedemissionsfromtheironandsteelindustryrepresent7.2percentofglobalgreenhousegasemissions.Avoidingrawmaterialextractionbypromotingsteelreuseandrecyclingisthehighestpriority,sinceproducingsteelfromscrapsavesaround60-80percentenergy.However,thereisagrowinggapbetweensupplyanddemandforbothreusablesteelcomponentsandscrapmaterialforrecycling.ShiftingfromblastfurnacestodirectreducedirontechnologycouldreducetheCO2emissionsfromprimarysteelproduction61-97percentoverthenext15-20years,farexceedingtheemissionsavingsfrommovingtobestavailabletechnologies(26percent),particularlyifcoupledwithashifttorenewableelectri-citysources.Othereffectivemeasuresincludereducingsteeldemandthroughextendingbuildinglifetimes,andsubstitutionwithcircularbio-basedmaterialssuchasengineeredtimberandbamboo.AluminiumAluminiumproductionishighlyenergyintensive,andwithelectricitybeingitsdominantenergysource,decarbonizingtheelectricitygridhasthelargestpotentialinthissector.Around27percentofallaluminiumproducedisusedinbuildingsandconstruction.Aluminiumproductionishighlyenergyintensivewhenproducedfromores,whereasproducingaluminiumfromscrapcanreducetheenergydemandby70-90percent.In2019,only34percentofaluminiumwasproducedfromoldandnewscrapduetotherapidgrowthindemandandthelonglifetimesofaluminiumproducts.By2060,aluminiumproductioncouldbemostlybasedonscrap,andproductioncouldbeelectrifiedusingrenewableenergysources.Theintegrationofaluminiuminbuildingsystemsisskyrocketing,anddecarbonizingaluminiumwillrequirenear-zero-emissiontechnologiesforrefiningandsmelting.PlasticsIncreasingplasticsrecyclingrequiresimprovementsincollection,sorting,andthepredominantmechanicalrecycling,plusmajoradvancesinchemicalrecycling.Plasticsareubiquitousmaterialswithhighgrowthratesandlowrecyclingratesoflessthan10percent.Mostgreenhousegasemissionsstemfromprimaryresinproduction(61percent),followedbyconversionprocesses(30percent)andend-of-lifeprocessing(9percent).Plasticsaccountedfor3.4percentofglobalgreenhousegasemissionsin2019,andin2015,16percentofplasticsintheUnitedStatesofAmericawereusedinbuildingsandconstruction.Plasticsareusedinapplicationsfromplum-bingpipestowindowframes,insulation,lining,buildingtextilesandpackaging.Ashifttowardsimprovedmethodsofplasticsrecycling,complementedbynovelbio-basedandbiodegradableplasticswhereverpossible,requiresmajorsupportforadvancesinplasticsproductionandrecycling.GlassThehighestinitialpriorityforglassshouldbedecarbonizingproductionandenablingwindowglassrecycling.Theuseofglasscouldcontinueinsimilarquantitiesastoday,orevenincreaseasareplacementmaterial,providedthatthereisgreatersupportforlocallyproducedandrecycledsources,andthattheimproperdesignofglassfaçadesdoesnotincreasecoolingrequirementsduringbuildingmain-tenanceduetoincreasedsolarheatgain.Conversely,thetransparencyofglasswillcontinuetobecriticalforon-sitesolarenergycollectiontechnologiesforroofsandfaçades,suchasdaylightharvesting,solarhotwatercollectionandpurification,andsolar-to-electricsystems.Increasingre-useandrecyclingwillrequiremuchstricterlegislation.Optionsfordecarbonizingglassproductionincludeswitchingtheenergysource,electrificationofallprocesses,processintensifica-tionandwasteheatrecovery.Inrenovationanddeconstruc-tion,off-sitewindowdisassemblyavoidscontaminationandallowsforglassrecycling.Earth-basedMasonryHighqualityearth-basedmasonryhaspotentialtoreplaceconcreteinmanylow-riseapplicationsbutneedsdevelopmentandregulation.Diverseearthmasonrymaterialsmadefromclay-richsoilandnaturalfibres,thataredriedinthesunorfired,havebeenusedformuchofhumanhistoryandareoftenre-used.However,xvBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREConcreteSteelAluminiumPlasticGlassTABLE0.1SUMMARYOFDECARBONISATIONSTRATEGIESPERMATERIALNON-RENEWABLEMATERIALS>Improvequarryrehabilitationandbiodiversityrestorationoflandscapes.>Reducetheclinker-to-cementratiowithalternativematerials.>Userecycledaggregates.>Electrifykilnsanduserenewableelectricitysources.>Integratecarboncaptureandstoragetoprovideadditionalstrength.>Minimizewastewithcomputationaldesign-for-disassemblyandre-use.>Minimizeon-sitewasteandemissionsthroughpre-fabrication.>Educatebuildingdesignprofessionalsinmaterialefficiency,optimization.>Developstandardsandbuildingcodesthatrequiremodularconcrete.>Incentivizerenovationoverdemolitionandbuildingcodesforrecycled.>Shiftfromblastfurnacestodirectreducediron(DRI)technology.>Electrifyallsteelproductionmethodswithrenewableenergysources.>Reducesteelusethroughacombinationofmaterialefficiencymeasures.>Avoidusingnewsteelbysubstitutingwithre-used(best)andrecycledmaterials.>Shifttolow-carbonalternativessuchasbio-basedmaterialsifpossible.>Adaptbuildingcodestoavoidoverspecificationandoptimizestructures.>Designwithpre-fabricatedelementsfordisassemblyandre-use.>Includematerialefficiencytraininginthecurriculaofarchitectsandengineers.>Ensurethatstakeholdersacrossthevaluechainusethesamemetrics.>Improverecyclingmethodstoenabletherecoveryanduseofmoresteel.>Reducedemandfornewaluminiumbypromotingre-useandrecycling.>Useelectricityfromrenewablesources(includinghydropower).>Imposestrictregulationstodesignforthecircularityofcomponentparts.>Standardizealuminumalloys/componentsforre-use.>Avoidoverspecificationanduseofprimarysourcematerial.>Electrifyheavyconstructionandtransportequipment.>Specifyhigh-performancebuildingenvelopes.>Maximizerecyclingandinvestinalloy-specificsortingandrecycling.>Certifydisassembledandre-usedcomponents.>Avoidtheproductionofnon-recyclableproductsthatharmthebiosphere.>Reducetheuseofplasticsinbuildingmaterials,wherefeasible.>Usebio-basedandbio-degradableplasticsproducedwithrenewableenergy.>Designfordisassemblyandre-use.>Standardizethechemicalcompositionsofpolymersforeaseofrecycling.>Increasetransparencyand/orstandardizechemicalcompositions.>Tracematerialusagetokeeptrackofavailablestock.>Increasemateriallifewithlow-carbonmaintenancepractices.>Investinmuchgreatercollection,sorting,andmechanicalrecyclingtoavoidproductionofnewplastic,complimentedbyimprovedchemicalrecycling.>Avoidnewdemandbyextendinglifetimesofbuildingsandcomponents.>Incentivizeandsupportlocallyproducedandrecycledglasssources.>Improveresearchonefficientmeltingtechniquestoavoidemissions.>Shiftglassproductiontobestavailabletechnologiesandrecycling.>Electrifyproduction,construction,andtransportwithrenewableenergy.>Useprocessintensificationandwasteheatrecovery.>Designstandardcomponentsandfaçadesurfacingforrecycling,re-use.>Designglassfaçadesthatminimizeheatabsorptionandreflectionandinsteadcapturesolarenergyforheating,cooling,waterandlighting.xviBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREMasonryTimberandWoodBambooBiomassLivingMaterialsTRANSITIONALRENEWABLEMATERIALS>Regulatequarryclosuretorestorenaturallandscapes.>Usestructuralandfacingbricktoincreaselongevityandreducemaintenance.>Replacehigh-carboncementbinderswithlower-carbonalternativebinders.>Usecement/mortaralternatives,suchasflyashwasteandsewagesludgeash.>Designmasonryunitsfordisassemblyandre-use.>Incentivizelocal,low-carbonearthmasonrymaking.>Educatedesignprofessionalsinmethodstoenhancethelongevityofnon-stabilizedearthmasonry.>Incentivizerenovationoverdemolition.>Incentivizeforestlandsownerstodevelopsustainablemanagementandbiodiversity.>Improvethedesignofforestbyproducts,toimprovecircularityintimber.>Improvecollectionratesof“clear-cuts”fromloggingpracticesandoff-cutsfromwoodmanufacturingforwoodproducts.>Improvewoodmanufacturingtocapturelossfromtimberprocessing.>Promoteandincentivizetheuseandre-useofstructuralmasstimber.>Trainandupskillconstructionactorsindesign-for-disassemblywood.>Updatebuildingcodestomandatereliablycertifiedproducts.>Incentivizetheresearchanddevelopmentofnon-toxicgluesandbinders.>Increasepolicysupportforcommercialenterprisestransitioningtohighlyproductiveandsustainablebambooforestmanagement.>Improvebambooplantpropagationmethods.>Transitionbamboomanufacturingtoon-siterenewableenergy.>Promotematerialefficiencybydevelopingstructuralstandardsfordifferentregionalspeciesandcirculardesign.>Incentivizetheuseofnon-toxicchemicalsandglues.>Integrateand/oradaptbamboostandardsforlocalbuildingcodes.>Educatearchitecture,engineeringandconstructionprofessionals.>Integrateintersectoralbiodiversebiomasssupplychainmanagement.>Incentivizeandinvestintechnologiesandbioadhesives.>Redirectbiomasstowardshigher-valueend-of-useproducts.>Createfinancialincentivesforthecaptureofbiomassbuildingmaterials.>Educateandtrainbuiltenvironmentprofessionalsindesign.>Educatestakeholdersoneffectivemaintenanceofproducts.>Educatefinanceandinsurancecompaniestoincentivizeadoption.>Implementmarketingandeducationprogrammes.>Trainandupskillmaterialrecoverymanagementtoimprovere-userates.>Understandnativeecologicalsystemsandcontextbeforeintroducingnewlivingbiomassmaterial;Usenativespeciesandorganicfertilizer.>Adaptdistrict-scalecarbonincentivesforimpactstourbanheatislandandstormwaterinfrastructure.>Designwithlow-carbonmaterialsubstructures,growingmedia,passivesolarenergy,andharvestedrainwaterforirrigation.>Provideavenuesforcircularcompostandwasteby-productrecovery.>Minimizematerialusethroughtheoptimizationofstructures.>Minimizeweightofmaterialsbyusinglesswaterandsoil.xviiBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREincreasinglymasonrybrickshaveadoptedtheuseofhigh-carboncementbindersandhightemperaturefiringtoaddressmechanicalandmoistureperformance.Iflocallymadewithlow-carbonbinders,additivesandprocessingmethods,earthmasonrycanregainitsroleasaviablebuildingmaterialformanyregionsandapplications.Emergingeconomieshaveacriticaloppor-tunitytoleapfrogoverthecarbon-intensivebuildingmethodsofdevelopedregionsEmergingeconomiesareinthemidstofanunprecedentedglobalconstructionboom,andthewindowfortransformingbuildingmaterialsandmethodsisnarrowing.Astheworldeconomyexpandsandaslivingstandardsrise,theglobaluseofrawmaterialsisprojectedtonearlydoubleby2060,underabusiness-as-usualscenario.Floorspaceworldwideissettodoubleby2060,andeveryfivedaystheworldconstructsenoughnewbuildingstoaddanothercitythesizeofParis.However,ashumanitycontinuestobuildmorerapidlythaneverinthequesttosecurecomfortandwell-being,thereisanimportantopportunityfordevelopingcountriestoleapfrogovertheunsustainablebuildingtechnologiesofthelastcentury,ifbindingcommitmentsaremadetoensurethecooperationofessentialstakeholdersacrossthesupplychains,fromproducersandgrowers,todesigners,buildersandowners.StrategiestoAlignStakeholdersAcrosstheWholeLifeCycletoEnsureGlobalCooperationonDecarbonisationThebuiltenvironmentsectorhasthepotentialtorapidlydecarboniseifsynergisticmeasuresaretakentosupportdiversestakeholdersacrossthelifecycleofmaterials–alifecyclethatspansacrossinternationalsupplychains.Rapiddecarbonisationofbuildingmaterialswillnotbepossiblewithoutsimultaneouslysupportingmaterialproducersanduserssuchasmanufacturers,architects,developers,communitiesandbuildingoccupants,tomakethedecisiontodecarbonise.Duetothecomplexityofthisinterconnectedsector,regulationandsynergisticenforcementisrequiredacrossallphasesofthebuildinglifecycle,fromextractionthroughend-of-use.Novelownershipmodelsthatreconcilethecurrently‘split’incentivesbetweenproducers,builders,ownersandoccu-pantsshouldbeencouragedinordertoenhancecooperativemodelsincreatingcirculareconomies,especiallyforhighvalueextractedmaterialssuchasnon-renewablemetals.Thecreationofnovelfutureownershipmodelsshouldbeencouragedwithinvestment.Forexample,aswithrenewableenergyandvegetationsystems,productionandconstructionconsortiumscould‘lease’and/ormaintainfacadesorotherhighvalueaddedmaterialcomponentsandmaintainthemthroughoutabuildinglifecycle,inordertoincentivisetheirongoingproductivity,longevityand/orreuseofmaterialsat‘end-of-life’.1.ImproveandIncreaseAccesstoReliable,TransparentDataCommonmetricsandconsistentassessmentprocessesallowdecision-makerstoaccuratelyweighthetrade-offsamongalternativedecarbonisationpathwaysandinformeffortstosetstandardsandtradepolicy.However,toolstovisualiseandassessdataneedtobemoreaccessible,transparentandverifiabletoallstakeholders.Wholelife-cycleassessmentscombineembodiedcarbonwithanticipatedoperationalcarbon,buttheimpactsonglobalecosystemsremainwidelyunder-estimated.Awiderrangeoftoolsareemergingtohelpdecision-makersgaineasieraccesstotherightdatatoassessthecarbonimpactsoftheirbuildingmaterialchoices;however,toolsandaccesstotransparentqualitydataneedstobeprioritised,withtheburdenofincludingsmalleractorssharedbyformalanddevelopedsectors.Withtherightaccessandtraining,readilyavailabletoolsformanaging,visualisingandcommunicatingthedatabehinddecisionscanbegame-changing.Toolsandframeworkscouldenablecomparisonoftheprosandconsofdifferentbuildingmaterialsintermsoftheirembodied,operationalandend-of-lifeclimategreenhousegasemissions.Datamanagementandvisualisationtoolsareemergingthatoffer“at-a-glance”scenariostosupportdecision-makinginrealtime.However,aswithenvironmentalassessmentsandcertifi-cationsacrossallsectors,theverifiabilityandconsistencyofdataremainsahugechallenge.Thesignificantrangeinthequalityandquantityofdataandcertificationprocessesacrossallmaterialsectors,eventhemostdevelopedones,resultsinuncertaintyonthepartofmaterialspecifiers,especiallyamongstdisadvantagedsmalleractors.Moreover,thechallengeacrossallglobalsectors,frominformaltoformalconstruction,istogettherightdatatotherightstakeholdersattheconsequentialstagesofdecision-making.Forthelatter,thereispotentialtobetterharnessbuildinginformationmodelsfromthedesignandconstructionphases,inordertobettertracktheimpactofmaterialdecisionsonthelifecycle.2.IncreaseInclusionandEnsureFairnessinCertificationandLabellingStandardsRisingpublicinterestinenvironmentallysoundconstructionpracticeshasledtoafloodofself-declaredenvironmentalclaimsfrommaterialproducers,withlimitedtraceabilityxviiiBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE0.1MunicipalbuildingenergycodesneedtotransitiontoincludeembodiedenergyVariousrequirementsandchallengesarenecessaryforsuchatransition.Source:AdaptedfromAmericanCouncilforanEnergy-EfficientEconomy2021..REGULATIONANDMARKETDEMANDBuildingspeciﬁcations,standardsandcodescanbeeffectivepolicyapproachestoacceleratetheshifttolow-emodied-carbonbuildingsbyinﬂuencinggeneralpracticeinthebuildingindustryandincreasingmarketdemand.BENCHMARKNoconsensusexistsonhowtobenchmarkorbaselinethelife-cycleembodiedcarbonofabuilding.Guidelinesareneededtoevaluatethetrade-offsbetweenembodiedandoperationalcarbon.DATAExistingdataandpoliciesareatthemateriallevelandfocusonmanufacturingprocesses.Moredataareneededonthedurabilityandresilienceofmaterialsanditsimpactonembodiedcarbon.CAPACITYManufacturers,constructioncompaniesandtradesneedtobuildtheircapacitytoparticipateindatacollectionandreporting.BUSINESSCASEBusinesscasesneedtobedevelopedformanufacturerstointegratebuildingdecarbonizationwithindustrialdecarbonization.Istheworldreadyforembodiedenergybuildingcodes?–generatingscepticismandbacklash.Internationalcoopera-tionisrequiredtoregulatefaircertification,verificationandlabellingfortradeacrossbordersandregions.Fortruedecar-bonisationofglobalmaterialflows,itisnecessarytoclosea“carbonloophole”thatdisadvantagesproducersfacingstrictpollutioncontrols.Inturn,itiscriticaltohelpsmallerprodu-cers,especiallyinemergingeconomies,toachievecertifica-tion,astheyareoftenunfairlypenalisedwithcross-bordercarbontaxesbecausetheycannotafford,orlackaccessto,faircertificationprocesses.3.EnforcePerformance-BasedBuildingCodesWiththegrowingadoptionoflow-cost,digitisedtrackingmethodsandaccesstodemand-sidemetricssuchasenergyandwateruse,performance-basedbuildingcodeshaveagreaterchancetoconnecttoarangeofstakeholdersacrosssectors,astheyseetheimpactoftheirchoicesaffecttheirfinancesandwellbeing.However,severalkeyimpedimentsstillneedtobeaddressedforwidespreadinclusionofembodiedcarboninbuildingcodes,alongsidetheimpactsofmaterialchoicesonglobalecosystemsandtheworkofthegeo-biosphere.4.EmpowercitiesandmunicipalitiesasdriversofchangetoImplementDecarbonisationattheDistrictLevelGovernmentsmustimprovemultilevelgovernanceframeworksandmechanismstobetterimplementandenforcebuildingsandconstructionregulationswhichsupportwholelifecycleapproachesandlowcarbonmaterialefficiencystrategies.Citiesmustbeempoweredtoimplementandenforcedecar-bonisationpoliciesincollaborationwithnationalandsub-na-tionalgovernmentinstitutionsaspartoftheirlocalactionplansforbuildingsandconstruction.Theyneedtopromotesustainableenergysolutionsandencouragepassivedesign,circularity,nature-basedandneighbourhoodlevelsolutions,incentivizingbuildingsandconstructionindustrystakehol-dersaschangeagents.Aschampionsforimplementingandenforcingclimatepoliciesandtargets,citiesareuniquelyplacedtocatalysethistransitionthroughtheirjurisdictionoverlanduse,authorityoverhousingprogrammes,roleinimplementingnationalpoliciesandbuildingcodes,andtheirroleincoordinatingwithlocalutilitiesandstakeholders.Thepublicsectorisofteninthebestpositiontoimplementdecarbonisationplansatlocalordistrictscale.Itcanhavemaximumimpactfornewdevelopment,sincestrategiesforxixBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREFigure0.2HumansarePartofLivingEcosystems:FrameworkfordignityacrossthebuiltenvironmentlifecycleSource:PartiallyadaptedfromInstituteforHumanRightsandBusiness(2022).LANDUSEDueprocessinlandacquisition,respectforindigenousandculturalrights,reducerawmaterialextraction,facilitatingurban-ruralcooperationandenforcingsustainableforestry,agricultural,andafforestationpractices,ensuresafeandfairworkingconditions.PLANNING+FINANCEInvestinnewmaterials,bestavailabletechnologies,andfacilitatecooperationtoincentiviseajust,circular,andbioeconomyacrossthelifecycle.Facilitatecooperationbetweenthebuilding,agrictulral,andforestrysectors.DESIGNPrioritisebuildingmaterials,interiorspacesandurbaninfrastrcturewhichsupportecosystemsdiversity,humanphysicalandmentalhealth,Inclusion,andaccessibility.CONSTRUCTIONConstructionworkers’rights,buldingsafety,responsiblesourcingofmaterials.Prioritisetheuseofmaterialswithcertiﬁcationofbothenvironmentallysustainableandfairlaborproductionpractices.MANAGEMENT+USEProvideopportunitiestoincreasethevalueandrightsofmaintenanceworkersandoccupantsbyreevaluatingtheimporanceofmaintainingmaterialsandlivingsystemsinacircularmaterialeocnomy.CIRCULARITYResponsibledisposal,re-useandreyclingofbuildingmaterials,approachtovacantlandandprojectlegacy.Promotebuildingre-use.HUMANDIGNITY+BIODIVERSITYACCOUNTABILITYPARTICIPATIONNON-DISCRIMINATIONDATATRANSPARENCYxxBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREindividualbuildingscanbeintegratedinsynergywiththedesignofsustainable,electrifiedgridsforthemanagementofenergy,water,wasteandtransport.Policiesandambitioustargetsfromlocalandnationalgovernmentsestablishleadingprecedentsforintegrateddecarbonisationacrossmultiplescalesofinfrastructureandbuildings.Thisisonlypossibleifmaterialchoicesandurbanplanningavoiddrivingupcoolingdemandsthroughthecreationofurbanheatislandsandinsteadlowerstheoveralloperationalcarbonofcitiesbymandatingbiomassmaterialsandothercoolsurfaces.5.HarnessPublicProcurementtoSupportDecarbonisationofMaterialsInmanyemergingeconomies,thepublicsectorcanplayacriticalleadingroleindemonstratingandenablingbuildingmaterialdecarbonisationthroughitsprocurementpowers.However,policygoalsfordecarbonisationmustbeformallylinkedtothepurchasingofmaterialsplanningphaseswithrigorouswholelife-cycleassessmentstoserveasexamplesforeffectivesolutionsacrossspecificlocalclimatetypesandbuildingtraditions.6.TackleGenderBiasinBothFormalandInformalBuildingSectorsGenderbiasisprevalentacrossthedifferentphasesofthebuiltenvironmentprocess.Inmanyformalsectors,thetwoprincipalissuestoactonare:1)closingthelargegenderpaygapsthatpersistacrossthearchitecture,engineeringandconstructionindustries,and2)addressingtheoverwhelmingdominanceofmeninseniordecision-makingandadminis-trativeroles.Acrossinformalsectors,theurgentprioritiesshouldbe:1)enforcingnationalandmunicipalregulationsforsafetyandimprovedworkingconditionsatconstructionsites,and2)promotingskilldevelopmentamongcasuallabourtoenablethetransitiontofairerandmoreconsistentlabourconditions.3)Intheshifttowardsbio-basedmaterials,criticalattentionshouldbeplacedonprotectingecosystemsandworkersfromtoxicityandenvironmentaldegradationfromunsoundagriculturalandforestrypractices.Inthecontextofmanyemergingeconomieswithapreponde-ranceofsemi-formalandinformalconstruction,governmentalprogrammesandpoliciesneedtoexpandwomen’saccesstonewtechnologies,marketinginformationandtrainingtosustaintheirparticipationontheground.Giventhatwomenfacebarrierstoaccessingcreditandloans,financialinstitu-tionsneedtoserviceanddesignloancollateralsystemsthataresuitabletoindividualsandwomencollectives.EnsuringReliableDataInordertogalvanisethemarketandtoenabledesigners,buil-dingowners,andcommunitiestomaketherightdecisions,toolstosupportthedecarbonisationofbuildingmaterialsrequiremorerapidprogress.Thesetoolsmustbesupportedbyaccesstobetterqualitydataandtransparentauditsconductedbyqualifiedthird-partyreviewers.Moresynergycouldbeleveragedincombiningthecertificationoffairlabourandenvironmentalpractices/workingconditions.Intheinformalsectors,stakeholderstypicallyhaveneithertheaccesstodatanorthemeanstoconductanalysesorcertifica-tion,thusgreatlydisadvantagingbothproducersandbuildersinemergingeconomiesfromdecarbonizingtheiroutput,forbothlocalandexportmarkets.Significantinvestmentintheresearchanddevelopmentofmethodsandstandardsisrequired,towardsbettermodelsofcoordinationacrossproducers,designers,builders,andcommunities,andwithregulationoffaircertificationandlabelling.Thebiggestchallengetothesemeasuresisthecomplexityandlackoftransparencyofinternationalsupplychainsforbuildingmaterials.Furthermore,therearesubs-tantialrisksthatneedtobeavoidedintheshifttobio-basedmaterials.Thebiodiversityandwellbeingofregionsmustbeimprovednotdegraded,withindigenouspopulations,womenandchildrenbeingmostat-riskofexploitationandtoxicexposuresintheagricultureandforestryindustries,potentiallycompoundingtheexistinggenderinequitiesintheconventionalbuildingsectors.Conversely,multiplestudiesshowthatthepresenceofwomenindecision-makingposi-tionsiscorrelativewithacommunalandcooperativefocusonsustainableresourcemanagementinmanyregions.Thevariabilityofclimates,agriculturalpracticesandspeciesaddstothecomplexityoffaircertificationandglobaltrade.Hence,internationalcooperationacrossbordersisessentialtowardsensuringajusttransitionwithregenerativeenvironmentalandlabourconditions.Thus,internationalcooperationiscriticaltosupportfaircerti-ficationandlabelling.Suchpoliciescanbesynergisticwithimprovingstrategiestodecarbonisetheembodiedenergyofmaterialswithintheformalsectorsacrosstheglobe,asthesearethesectorsthatareproducingthemajorityofcarbonemissionsinthebuiltenvironmenttoday.Thus,theresponsi-bilityforseedinganewmarketplaceandgalvanisingafuturenetzeroeconomyforthebuiltenvironmentsectorshouldbespreadacrossproducersandconsumerswithintheformalglobalbuildingsectors,bothpublicandprivate.xxiBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE1.SettheVision,LeadbyExampleandImproveMulti-LevelGovernance>Developnationalandsub-nationalroadmapsandactionplansandinstitutionalisingcoordinationmechanismstofacilitatecollaborationbetweenactorsandensurethatthesearenotaffectedbyshort-termspoliticalcycles.>Empowercitiesandmunicipalitiesasdriversofregionalchangebyunde2.MakeCarbonVisiblethroughImprovedDataAccessandQuality>Promoteclearandconsistentstandardsforcarbonlabelling.ProductsshouldbecertifiedwithinternationalstandardssuchastheGHGProtocolProductStandard,ISO14067orPAS2050,withmoresupportforenforcingfairregulation.>Mandatethelifecycleassessment(LCA)ofthecarbonimpactofbuildingmaterialsandfundresearchtodeter-minebestpracticesforlife-cycleanalysisofecosystemimpacts.>Purchase,provideorsubsidisedataneededforassess-mentsforkeystakeholders.>Dramaticallyincreasethesupportforongoingtooldevelopmentanduseforstakeholdersacrossthesupplychaintobeabletomakerapidandreliabledesignandprocurementdecisions.>Encouragedigitalisationandthedevelopmentofbuildingpassportstoassistinstandardisingdatatobetraceable,transparent,andverifiable.>Fundresearchtofurtherdevelopdatabanks.3.Adaptnormsandstandardstoallowfortheuseofcircular,alternativeorlower-carbon,bio-basedbuildingmaterialsandconstructionpractices>Introducing/strengtheningperformance-basedbuildingcodesthatincludeembodiedcarbon,mandatingthetran-sitiontolowcarbon(andrenewable,ifpossible)materials.>Acceleratetheindustrytransitionbysupportingtherapiddecarbonisationofconventionalmaterials,throughelec-trificationwithrenewablesanddramaticallyincreasingtheR&Dbudgetsandpublic-privatepartnershipstowardsinnovationofcircular,decarbonisationandcarboncaptu-ringtechnologies.Insummation,wholesaledecarbonisationofbuildingmate-rialswillnotbepossiblewithoutsupportingandregulatingsynergisticmeasuresacrossthesupplychainandlifecycleofthedifferentmaterialsectors,fromextractionthroughend-of-useandcircularreuse.Policymakersmustengageactorsacrosstheentirevaluechaintowardsthethreemaindecarbonisationprinciplesdiscussedinthisreport:1)Avoidmaterialoveruseandnewmaterialextractionbybuilding(with)less,activelyseekingwaysofreusingandrecyclingbuildingsandmaterials;2)Shifttosustainablyproducedlowcarbonrenewablebuildingmaterialssuchasearthandbiobasedmaterialswheneverpossible;3)Improvemethodstodecarbonisecarbon-intensiveconventionalmaterialssuchasconcrete,steelandaluminium,andonlyusethemwhennecessary.Acrossregions,implementationmethodswillvaryaspatternsinmaterialflowscenariosdiffer.Inhighlydeve-lopedregions,incentivesneedtofocusontherenovationofexistingandageingbuildingstock,whereasindevelopingregionswithrapidruraltourbanmigration,andrampanthousinginsecurity,thereisanopportunitytoradicallyre-inventnewconstructiontechniquesandleapfrogoverpriormodernpracticesbyreconnectingwithexisting,localclimate-specificbuildingknowledgeandvernaculartradi-tions,whiledramaticallyimprovingconventionalmaterialproduction,andshiftingtosustainablysourcedbiomaterialswhereverpossible.Todrivemarkettransformationandstakeholderaction,governmentsshouldtakeactionto:TOUNBLOCKRESISTANCE,POLICYMAKERSMUSTENGAGEACTORSACROSSTHEVALUECHAINPOLICYRECOMMENTATIONSFORDECARBONISINGMATERIALSINTHEGLOBALBUILDINGSECTORxxiiBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE4.IncentiviseCircularEconomyApproachesforRe-UseandRecycling>Incentivisebuildingdesignsthatlastaslongaspossibleand,wherepossible,incorporatedesignfordisassemblyandmodularconstructiontofacilitateend-of-liferecy-cling.>Adoptrenovationpoliciesthatencouragethediversionofend-of-lifematerialforrecoveryandrecycling,promoteregulationandmeasuringofwholebuildinglife-cyclecarbonemissions,incorporatedesignfordisassembly,andprovidequalitylong-lastingmaterialassembliesinretrofitsolutions.>Promotetheconsiderationofend-of-usestrategiesduringmaterialspecificationinthedesignofnewbuil-dingsandrenovationsolutionstoavoidwasteandasso-ciatedemissionslaterinthebuildinglife.>Incentiviseamarketplaceformaterialre-useanddevelopstandardstoensurethequalityandefficacyfortheiruse,inordertoprovideassurancetoactorsinthebuildingsector.5.PromotetheTransitiontoLow-Carbon,BiodiverseMaterials>Adoptboth“push”and“pull”marketapproachestoscaleupsustainablebio-basedbuildingmaterials,bypushingtocreateconsumerdemandbysupportinglow-carbonbuildingmaterialenterprisesatthelocalandbioregionalleveltodevelopandmarketnewproducts,whilstcultiva-tingbroadpublicinterestandeducationthroughpowerfuladvertisingandpubliceducationcampaigns.>Accelerateinternationalandlocalregulatoryframeworkstonormaliseindustryadoptionofbio-basedmaterials,includingbystandardisingmaterialperformancecriteria,integratingthesematerialsintobuildingcodesandtrainingstakeholdersinthemainstreamconstructionindustry.>Dramaticallyreducetheriskofregionalforestfiresandincreasethecarbonsequesteringproductivityofregionalforestsandagriculturallandsbyfacilitatingeducationandinvestmentinenterprisesfocusedoncollection,cleanincinerationandupcyclingofforest,agriculturalandbiomassresourcestowardsintegrationintobinders,finishesandstructuralproducts.6.EnsureaJustTransitionThetransitiontobio-basedandcircularmaterialecono-miesmayexacerbatetheserisksacrossthesupplychain,especiallyininformaleconomieswherebuildingcodesareextremelydifficulttoenforce.Therefore,itiscrucialthatgovernmentsseizetheopportunityofcouplingsocialandenvironmentaljusticewithfairandvisiblelabellingandcerti-ficationprocessestoraiseawarenessamongconsumers,sincethetwoissuescombinedmayultimatelyhavegreatermarket‘pull’thaneitherissuelabelledseparately.>Engagestakeholdersacrossthesupplychainbyfundingjusttransitionprograms,labellingandcertification.>Anticipateandfundproblemareasforajusttransition,particularlyinconventionalhigh-carbonmaterialsectors.>Highlightandencouragetheresolutionofexistinginequi-ties.>PromotethewidespreaduseofJustTransitionplanningToolkitssuchasbyClimateInvestmentFundsandDesignforFreedom.>Supportindustrytosecureworkersandtheircommuni-tiesaffectedbydownscalingofconventionalprocessesandencouragesynergieswithnewopportunitiesandreplacementmethodsthatarebiobasedorcircular.>Encourageinclusiveandtransparentplanning.>Strengtheninternationalactionandcollaborationforcollectiveimpacts.>Incentivisegenderinclusioningovernmentcontractsandprioritiseprojectapprovalsforcompaniesthatpromotewomentoleadershippositions.>Enforcenationalandmunicipalregulationsforsafetyandimprovedworkingconditionsatconstructionsites..7.StrengthenInternationalActionandCollaborationforCollectiveImpact>Promoteclearandconsistentstandardsforcarbonlabel-ling.>EnsurethatregulationandenforcementofdomesticcarbonlabellingmatchesISOstandards.>Establishaninternationalstandardscommitteeforcarbonimpactlabellingofbuildingmaterialstoaddressdiscrepanciesinmethodsandqualityandcreatepathwaystowardsenforceableregulation.>Closethe“carbonloophole”incarbonoffsetsbydeve-lopingaslidingscaleofrelevance,wherebytheprocessxxiiimostcloselyassociatedwiththeactualdecarbonisationofmaterialprocessesgetsthemostcredit.>Developtrademechanismstosupportemergingecono-mies.>Ensureafairplayingfieldforlow-carbonbuildingmate-rialsthroughinternationalandmultilateralengagement.Inconclusion,thebuiltenvironmentsectormustlearntodesignwithnature-basedprocessesifitistodecarbonise.Thismeansreducingtheburdensonthegeobiospherefrom“extracted”,toxic,non-renewablematerials,andincreasingregenerative,renewableandcircularmaterials.However,allmaterialsectorsneedtobeincludedandpoliciescancreatesynergisticopportunitiesforbothconventionalandemer-gingindustries.Forexample,decarbonisationofthecementsectorandothermajoremitterscanbeenhancedbyshiftingtobio-basedbindersandotherlow-carbonreplacements.However,manyoftheseemergingdecarbonisationmethodsareoftennotyetcostcompetitive,andwidespreadbiasesremainthatprotectentrenchedmethods.Sustainablyscalingupimplementationcannotbeenforcedwithoutsubstantialinvestmentinresearchanddevelopmentalong-sideincentivesand/orenforceablebuildingcodes.Althoughtheshiftfromextractingtogrowingbuildingmaterialspresentsmajoropportunities,therearesubstantialdangersofanunregulatedshifttowardsbiomaterialsbackfiringandcausingunmitigatedenvironmentaldegradation.Thus,internationalcooperationiscritical.Policiescanbesynergisticwithimprovingstrategiestodecarbonisetheembodiedenergyofmaterialswithintheformalsectorsacrosstheglobe,asthesearethesectorsthatareconsu-mingandproducingthemajorityofcarbonemissionsinthebuiltenvironmenttoday.Attheinternationalclimatelevel,actionisrequiredforcountriestoaddressembodiedcarbonintheirNationallyDeterminedContributions(NDCs)towardsreducingemissionsundertheParisAgreement,andthenextstepstowardsensuringfirmcommitmentsneedtobelegis-latedthroughenforceablebuildingenergycodes.Despitethemassivecontributiontoglobalemissionsfromembodiedcarbonwithinbuildingmaterials,ithaspreviouslybeenunder-addressedinstrategiestoreducebuildingemissions.Thus,theresponsibilityforgalvanisingafuturenetzeroeconomyforthebuiltenvironmentsectorshouldbespreadacrossproducersandconsumerswithintheformalglobalbuildingsector,bothpublicandprivate,inordertobolsterthetransitiontoaclean,just,renewable,circularbuildingmaterialseconomy.NEWECONOMICMODELSAREREQUIREDTHATENHANCECOOPERATIONANDREPAIRSPLITINCENTIVESACROSSSTAKEHOLDERSxxivBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREPOLICYMAKERSFINANCIALINVESTORS+DEVELOPERSMANUFACTURERS,BUILDERS+WASTEMANAGERSARCHITECTS,ENGINEERS+OCCUPANTSWORKOFTHEGEO-BIOSPHERE>Policiestoreduceextractionofnon-renewablematerials>Facilitateinnovationinbiodiverse,circularforestryandagriculture>Useeconomicpracticesthatvaluenaturalcapitalandbiodiversity>Committogenderequity+fairlabouracrossprojectlifecycles>Avoidunsustainableland-usepatterns,soildegradationandforestrypracticesinsourcingbothconventionalandbio-basedmaterials>Considerthesourceandrecoveryrateofnon-renewableandrenewablematerialswhendesigningmaterialsDESIGN>Enforceperformance-basedbuildingcodes>Developfairgreencertificationsandtransparentlabelling>Incentivizetoolsfordata-drivendesign>Investindesignofrecycled,re-usedandbio-basedmaterialsandcomponents>Investinaccessibledatavisualizationframeworks>Committothedevelopmentofcircularcomponents>Developmaterialstooptimizerecyclability>Developbio-basedalternatives>Designforlongerlife>Increaseeducationindecarbonisationstrategies>Computation/design/optimizationoflocalmaterialsforre-usePRODUCTION>Electrifythegrid>Mandaterecyclingandbestavailabletechnologies(BAT)>Mandateforestandmaterialmanagement>Improvecertifications>Investininnovationforlow-carbonmaterialsandbinders>Investinnewlow-carbonmethods>InvestinBATequipment>Upgradeplants>Avoidprimarymaterials>Circularmanufacturingandcompositesforre-use>Committofairlabour>Workwithproducerstospecifycircularmaterials>Designdevelopmentofalternativebio-basedmaterialsandcomponentsCONSTRUCTION>Mandategreencertifications>Mandatethird-partyverificationofsiteprocessesandemissions>Incentivizeoff-sitecircularmanufacturing>Increaseenergy-efficientfinancing>Improvefinancingforrefurbishmentandrenovationofexistingbuildingsandmaterials>Committofairlabour>Tracematerialuse>Electrifyallequipmentwithrenewableenergy>Requireenergyefficiency>Improvetraining>Committofairlabour>Manageon-sitewastethroughpre-fabrication>Improvemanagementofon-siteconstructionwithcirculardesignUSE>Adoptbuildingenergycodesthatmandatematerialssupportinghigh-performanceenvelopestoreduceoperationalcarbon>Incentivizerenovationovernewconstruction>Developfinancialtoolstoincentivizelowcarbonmaterialselectionbyreconizingenergyandcostpay-backperiods>Supportbuildingownersandoccupantstoselectlow-carbonalternativesthroughsupplychaindevelopment>Increasemateriallifewithlow-carbonmaintenancepractices>SelectmaterialsthatreduceoperationalcarbonENDOFUSE>Certifypre-usedcomponents>Buildingcodestomandatere-use>Plancitiestoincorporatetransferplants>Regulatedemolition>Provideeconomicincentivestoavoiddemolitionbyrefurbishingbuildings,increasingre-useandrecycling>Improverecoveryandon-sitesortingofmaterials>Standardizematerialstoimproverecycling>Designfordissasemblyandre-Use>IncreasecontinuingeducationforstudentsandprofessionalsinnovelcircularmaterialstrategiesTABLE0.2BUILDINGLIFECYCLEPHASESWHODOESWHATTODECARBONISEMATERIALS?xxvBUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE1Urbanisationisrisingandsoisthedemandforbuildingmaterialstoconstructglobalcities.BUILDINGMATERIALSAreSettoDominateClimateChange1.1TheBuiltEnvironment’sImpactonGlobalCarbonEmissionsThebuiltenvironmentsectorcontributes37%ofenergy-relatedcarbonemissions.Thebuiltenvironmentsectorisoneofthelargestcontribu-torstoclimatechange,responsibleformorethanathird(37percent)ofglobalenergy-relatedcarbonemissions(UnitedNationsEnvironmentProgramme[UNEP]2022,seeFigure1.1).Yetthebuiltenvironmenthasreceivedonlyasmallfractionofclimate-focusedfundingforresearchanddeve-lopmentcomparedtoothersectors.Althoughinvestmentsintheenergyefficiencyofbuildingoperationsincreased16percentamongGroupofSeven(G7)countriesin2021(ibid.),suchcommitmentspaleincomparisontowhatisrequiredtodecarbonisethebuiltenvironment.Asthelargestglobalindustrialisedsector,constructionalsohaswidespreadsocialimpacts;itisatthehighestriskofforcedlabour,withlaxenvironmentalandlabourregulationstendingtocoincide(GraceFarmsFoundation2022).Asbothpopulationandwealthcontinuetogrowglobally,humanityisbuildingmorethaneverinaquesttosecurecomfortandwell-being.Floorspaceworldwideissettodoubleby2060,andeveryfivedaystheworldaddsenoughnewbuildingstototalthesizeofParis(UNEnvironmentProgramme[UNEP]andInternationalEnergyAgency[IEA]2017).Accordingtoa2019reportfromtheOrganisationforEconomicCo-operationandDevelopment(OECD),theglobalconsumptionofrawmaterialswillnearlydoubleby2060astheworldeconomyexpandsandlivingstandardsrise,doublingtheenvironmentaloverloadingbeingexperiencedtoday.TheOECDprojectsthatifwecontinue“business-as-usual”practices,thebiggestincreaseinresourceuseby2060willbeinextractiveminerals,particularlyindevelopingeconomies(OECD2019).Thesemegatrendsarealsoinfluencedbyrapidurbanisation.In2020,the124countriesthatdominatethedevelopingworldwerehometo81percentoftheworld’spopulation,andthisshareisprojectedtoreach87percentbytheendofthecentury(RoserandRodés-Guirao2013;UnitedNationsDepartmentofEconomicandSocialAffairs2020;WorldBankn.d.).Muchofthisfuturepopulationgrowthwilloccurincities.TheWorldBankestimatesthattomeettherapidincreaseinurbanpopulations,300millionadditionalhouseswillneedtobeconstructedby2030(WorldBank2022a).Enablingthisglobalbuildingboomrequiresanewagendafordecarbonisationtomeetresidentialneedsofdevelopingcountrieswhiledecarbonizingthefullrangeofbuildingtypesglobally,fromformaltoinformal(seeBox1.1).Intheabsenceofurgentaction,thecarbonemissionsofcommonconstructionmaterialssuchasconcrete,steelandaluminiumareprojectedtogrowtoincreasinglydangerouslevels.Althoughdevelopedcountrieshavehistoricallycontributedthevastmajorityofglobalcarbonemissions,theworld’stop10greenhousegas-emittingcountriesnowincluderapidlydevelopingcountriessuchasChina,IndiaandIran(IslamicRepublicof)(Nejatetal.2015).Evenwiththeimplementationofwidelyacceptedinterventions,emissionsfromthebuiltenvironmentsectorareprojectedtogofarbeyondwhatisallowabletokeepglobaltemperaturerisewithin1.5degreesCelsius,thetargetsetunderthe2015ParisAgreementonclimatechange(Caoetal.2021).Thisreportoutlinesconcretepathwaystoreversetheseprojections,andeventoreachnetzeroemissionsinthebuiltenvironmentsectorbymid-century,throughthepromotionofbestavailabletechnologiesforconventionalmaterials,combinedwithamajorpushtoadvancecircularrecyclingandbio-basedmaterialsfromforestandagriculturestreams.1.1Globalcarbonemissionsfromthebuiltenvironmentsector,bysource,2021Thebuiltenvironmentsectorisresponsibleformorethanathirdofglobalenergy-relatedcarbonemissions.AdaptedfromUNEP2022.255075100GlobalshareofbuildingsandconstructionoperationalandprocessCO2emissions,20212050BusinessasUsualProjection2021ProjectedContributionsfromEmbodiedandOperationalCarbonwithintheBuildingSectorFrom2021to2050withBusinessasUsualProjections75%25%51%49%37%TransportOtherIndustryOther6`%11%3%8%6%InfrastructureandotherConstructionIndustry3%ofBuildingSectorCarbonEMBODIEDOPERATIONALResidential(Direct)Residential(Indirect)Non-Residential(Direct)Non-Residential(Indirect)EstimatedEmissionsforBricksandGlassBuildingConstructionIndustryConcrete,Aluminium,Steel©AscentXmedia/iStockphoto1BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREBy2030,3billionpeopleworldwideareexpectedtorequireaccesstoadequate,affordableandcomfor-tablehousing(UnitedNationsn.d.).Muchofthisdemandwillbeintherapidlyurbanizingdevelopingworld.However,mostglobalstudiesonhousinggrowthto-datehavefocusedonformalbuildings,includingsingle-family,multi-familyandhigh-risetypesfoundindevelopedcountries(Marinovaetal.2020).Recently,agrowingliteratureisdetailingtheadditionaldiversityofbuildingsindevelopingcountries(Pikholz1997;deWetetal.2011;MalikandBardhan2018;Mehrotra,Bardhan,andRamamritham2018;Nutkiewicz,JainandBardhan2018).Onestudydefinedthreecategoriesofbuildingtypesworldwide—formal,informalandsemi-formal—withthemostcommondifferingcharacteristicsbeinginconstructionmaterialsandstyle,size,durabilityanddemographyoftheresidents(seeTable1.1)(Iyer,RaoandHertwich2023).Asof2016,morethan1billionpeoplelivedininformalhousingslumsandlackedaccesstodurablehousing,alongwithotherbasicamenities(UN-Habitat2016).Becauseformalbuildingsaretypicallymoredurablethantheothertwotypesofbuildings(Iyer,RaoandHertwich2023),manylow-andmiddle-incomecountriesseektoredevelopinformalhomesandtorelocateresidentstonew,formalconstructions(Kharche2020).However,studieshaveshownthatresidentsinsemi-formalandinformalhousingoftenhavethrivingsociallivesandasenseofcommunity(Bardhanetal.2018;Sanyaln.d.),whereasinformalapart-mentbuildingstheymaybemoreisolatedsocially(Debnath,BardhanandSunikka-Blank2019).Resettledinhabitantsoftenendupmovingbacktoinformalsettlementsfromtheirnewformalhomes,whetherforsocialreasons,tobecloseTable1.1CategorizationofbuildingsworldwidebasedondurabilityandotherfactorsFormalSemi-formalInformalDurabilityHighMediumtolowLowConstructionReinforcedNotfullyreinforcedNotreinforcedNumberofNorestrictionsTwotothreeOnetotwofloorsIncomeclassMiddletohighLowtolower-middleLowofresidentsSource:Iyer,RaoandHertwich2023.toworkplaces,toreducecostsorotherfactors(Debnath,BardhanandSunikka-Blank2019).Moreover,redevelopedformalbuildingsareoftenpoorlydesignedandrarelytakeintoconsiderationthepreferencesofrelocatedresidents.Insufficientcookingandoutdoorspaceandpooraestheticsarecommonissuesfacedbyresidents,addingtotheirmotivationtomovebacktohorizontalslums(Debnath,BardhanandSunikka-Blank2019).Basedonthesefindings,policymakersneedtoensurestakeholderparticipationindecision-makingprocesses,especiallypertainingtoslumredevelopment.Beingawareandinclusiveofthelifestyle,needsanduniqueconstraintsfacedbytheselow-incomeinhabitantsmightimproveredevelopmentsuccessrates.However,acompleterehabilitationofinformalsettlementsisunlikely.Thus,researchneedstofocusonimprovedmaterialsinthebuildingenvelope,improvingthermalcomfortforinhabitantsandreducinglife-cycleenergydemand.Additionally,retrofitswithlow-costpassivecoolingmaterialsmustbeinvestigatedforinformalandsemi-formalbuildings,toprovidethermalcomfortinthetransitiontowardsmoredurablehomes.Thisisespeciallykeyastheselow-incomehomesperformespeciallypoorlyinprovidingthermalcomfortinaheatingworld,asinhabitantsarepricedoutofcommonmechanicalcoolingtechnologiesandappliances.BOX1.1THENEEDTOADDRESSTHEFULLRANGEOFBUILDINGTYPESGLOBALLYINDECARBONISATIONEFFORTS©Adelaide&RuralSalvage2BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE1.2Globalmaterialflows,bytype,1945versus2015Biomassmaterialsdominatedinbuildingsuntilthelatterhalfofthe20thcentury.Source:Haasetal.2020.1.2WeUsedtoBuildwithLow-CarbonMaterialsEvenintheveryrecentpast,buildingmaterialswerenotalwayscarbonintensive.GiventheincreasinglyfuriouspaceandscaleoftheglobalcGiventheincreasinglyfuriouspaceandscaleoftheglobalconstructionboom,thechallengeofshiftingawayfromcarbon-intensivematerialsandmethodsoftenseemsdaun-tingandpotentiallyimpossible.Butitisimportanttorecallthatevenintheveryrecentpast,buildingmaterialswerenotalwayscarbonintensive.Upuntilthemid-20thcentury,globalmaterialflowswereextractedoverwhelminglyfromrenewable,biologicalsourcessuchasforestsandagricul-turalprocesses(seeFigure1.2).Thevastmajorityofbuildingmaterialswerelocallysourced,andbuildingswerespecifi-callydesignedwithclimateconditionsinmind.Biomassmaterials–includingwoodandtimber–dominatedglobalconstruction,alongsideearth-basedmaterials,untilthelatterhalfofthe20thcentury.Ithasonlybeeninthelastseveraldecadesthatthemajorityofbuildingmaterialscomefromextractive,toxic,non-renewableprocesses.Bythelate20thcentury,apreponderanceofmetalsandmineralsconstitutedthemost-usedbuildingmaterialsforthefirsttimeinhumanhistory.Justthreematerials–concrete,steelandaluminium–areresponsiblefor23percentofoverallglobalemissionstoday(GlobalAllianceforBuildingsandConstruction[[GlobalABC],InternationalEnergyAgency[IEA]andUNEP2019).Withcooperationacrossglobalsectors,wecanalterthispath.Theshifttowardsproper-ly-managedbiobasedmaterialscouldleadtoacompoundedemissionssavingsinthesectorofupto40percentby2050inmanyregions.Toenabletheshifttowardsnewmethods,itisimportanttounderstandwhatdrivesthedecisionsbeingmadeateachphaseofthebuiltenvironmentprocess.Buildingmaterialscarryenormousculturalsignificance.Thereasonsthatsocietieschoosetobuildwithcertainmaterialsoverothersarecomplexandaredrivenbydiversesocial,technicalandeconomicfactors.Commoncarbon-intensivematerialssuchasbricks,concrete,steelandglassareresponsiblefortheimageandculturalcurrencyofcities,institutionsandhouses.Theyreflecthowacommunityhasorganisedovertimeandwhatithasvaluedduringdifferentperiodsofitshistory.Insidebuildings,wheremodernsocietyincreasinglyspendsthemosttime,interiorfinishessuchaswood,plasterandceramicsdefinethe“lookandfeel”ofhowpeopleexperiencetheirhomesandworkplaces,withsignificantimplicationsforhealthandwell-being.ExtractionProduction19452015Endoflifewatervapouremissionssolidandliquidwastewatervapouremissionssolidandliquidwasterecycledstoredrecycledstoredusedformaterialusedforenergyusedformaterialusedforenergyfossilmaterialsbiomassmetalsandminerals3BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURETHESHIFTTOBIOBASEDMATERIALSMAYSEEMDAUNTING,BUTUPUNTILTHEMID-20THCENTURY,THEVASTMAJORITYOFBUILDINGMATERIALSWERELOCALLYSOURCED,LOW-CARBON,ANDSPECIFICALLYDESIGNEDWITHCLIMATECONDITIONSINMIND.4BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE1.3StructureoftheReportThisreportisorganisedinthesamemannerrequiredforbuildingdecarbonisation.Becausebuildingsareintegratedsystems,comprisingmanymaterialsproducedindisparateregionsacrosstheglobe,thereisnosinglestrategy.Ratheritisimportanttocarefullycultivatetheabilityfordecision-makerstotakesynergisticmeasuresacrossmultiplematerialsectorsandatmultiplestagesinthelifetimeofbuildings.Thisreportoffersaguidetoapplyinga“wholelife-cycleapproach”tothebuiltenvironmentsectorandgivesdecision-makersasetofcompoundingstrategiestoapply.2LIFECYCLETHINKINGChapter2providesbackgroundonthemainsourcesofcarbonemissionsfromthebuiltenvironmentsector–embodiedandoperationalemissions–andoutlineshigh-levelstrategiesforadoptingawholelife-cycleapproachtothebuiltenvironment,particularlyaroundembodiedcarbonandbuildingmaterialchoice.3AVOIDChapter3providesspecificguidanceforkeyactorsaboutwhatactionsshouldbetakeninwhatcontextandalongwhattimelinetoachievemaximumdecarbonisationthroughcircularmaterialstrategies.Itfocusesspecificallyonthestrategiesofavoidingwaste,building(with)lessandimprovingcircularity.4SHIFTChapter4considersthefullimplicationofarevolutionaryshifttowardsbio-basedmaterials–withallofthepotentialpitfallsandnecessarytechnologicaldevelopmentsthatmustbesupportedinordertosuccessfullyscaleuplow-carbonbiomaterialswhileachievingnetbiodiversity.5IMPROVEChapter5lookscarefullyattherangeofconventionalbuildingmaterialschoices,theircarbonimpactsacrosstheirlifespans,andimportanttechnologicalandmarketshiftsandtrendsassociatedwiththem.Itfocusesspecificallyonwaystoimprovetheirproductionanduse(whennecessary)inordertodecarboniseconventionalmaterialprocessing.6TOOLSChapter6providesinformationonexistingandemerginganalyticaltoolsforassessingcarbonimpactsacrosstheentirebuildinglifecycle.Itoutlinestheneedfordistrict-scaleplanningandglobalstandardsandlabelsforemissiontransparency.7POLICYChapter7outlineskeypolicyrecommendationstoillustratetheseprinciplesinreal-worldscenarios8CONCLUSIONChapter8providesabriefconclusionanddiscussion.Overall,thereportshowsthatadoptingawholelife-cyclestrategyfordecarbonizingthebuiltenvironmentprocessmeans:buil-dinglessorbuildingwithless,incorporatingcircularmaterialsstrategiesintonewandexistingbuildings,designingbuildingswithlowerlifetimeoperationalemissions,andacceleratingtheuseoflow-carbon-intensitybuildingmaterials.©VladimirMelnik/Shutterstock.comReducingembodiedandoperationalemissionsrequirescooperationacrossmultiplestakeholdersthroughoutthebuildinglifecycle.LIFECYCLETHINKINGDecarbonisationRequiresaWholeLife-CycleApproach22.1EmbodiedversusOperationalCarbonEmissionsinBuildingsAbuilding’scarbonfootprintreflectsitscombinedembodiedandoperationalcarbon.Transitioningtolow-carbonbuiltenvironmentsrequiresthedesignofmaterialstrategiesthathavemultiplebenefitsandthattakea“wholelife-cycle”approach,inlinewiththeprinciplesofacirculareconomy.Toappreciatethevalueofsuchanapproach,itisimportanttofirstunderstandhowandwheremostofthegreenhousegasemissionsfromthebuiltenvironmentaregenerated.Theseemissionsarebroadlysplitacrosstwocategories:embodiedemissionsandoperationalemissions(seeFigure2.1).Understandingthedifferenceiskeytodecarbonizingthebuiltenvironmentsector:2.1EmbodiedandoperationalcarbonemissionsAbuilding’scarbonfootprintoveritslifespanisthesumofitsembodiedplusoperationalemissions.AdaptedfromMagwoodetal.2021.>Embodiedemissionsarealltheemissionsassociatedwiththeconstruction(anddeconstruction)ofabuilding.Theyaregeneratedduringtheextraction,manufacturing,transportandon-siteconstructionofbuildingmaterials(newbuildingsaswellasrenovations)andat“end-of-life”demolition,or,preferably,re-usefornewbuildings(GlobalABCandUNEP2021).>Operationalemissionsaretheemissionsgeneratedthroughthefunctionandmaintenanceofthebuilding.Theyarereleasedwhilemaintainingthebuilding’sindoor“comfortlevels,”includingbyheating,cooling,lightingandelectricalappliances.Theinitialdesignchoicesforabuilding(suchasthebuildingmaterialsused)aswellasupgradingmaterialsduringrenovations,havesignificantimpactsontheamountofoperationalcarbonandonopportunitiesforrecycling.Withinthetotalshareofemissionsfrombuildingandconstruction(37percent),themajority(11percent)areindirectoperationalemissionsfromresidentialbuildings(seeFigure1.1).However,atleast6percentareembodiedemissionsfromthemostcommonlyusedbuildingmaterials:concrete,steelandaluminium.Inrecentyears,considerableattentionhasbeenfocusedonhowtoreduceoperationalcarboninthebuiltenvironment,asitcurrentlycontributesthelion’sshareofemissionsfromthesector(75percent)(seeFigure2.2).However,theshareofembodiedcarbonofmaterialsisprojectedtosurgefrom25percenttonearlyhalf(49percent)bymid-century(OECD2019).Meanwhile,theshareofoperationalcarbonwillshrinkaselectricitygridsincreasinglytransitiontorenewableenergyandasbuildingoperationsbecomemoreefficient(Architecture20302022).Asabuilding’soperationalemissionsshrink,theshareofembodiedemissionswillgrow.Figure2.3illustrateshow,overabuilding’slifespan,annualemissionsfromoperationalcarbon(purplebars)willcontinuetodecreaseasthegriddecarbonisesby2050.Meanwhileembodiedcarbon(orangebars)willremainhigh,ifmeaningfulactionisnottakentoreduceit.2.2ProjectedcontributionsfromembodiedandoperationalcarbonwithinthebuildingsectorUnderbusinessasusual,embodiedemissionswillcontributenearlyhalfofallbuildingemissionsbymid-century.AdaptedfromArchitecture20302022.EnergyUseIntensityEnergySourceLIFE-CYCLECARBONEMISSIONSEMBODIEDCarbonEmissionsOPERATIONALCarbonEmissions©Nualaimages/Envato255075100GlobalshareofbuildingsandconstructionoperationalandprocessCO2emissions,20212050BusinessasUsualProjection2021ProjectedContributionsfromEmbodiedandOperationalCarbonwithintheBuildingSectorFrom2021to2050withBusinessasUsualProjections75%25%51%49%37%TransportOtherIndustryOther6`%11%3%8%6%InfrastructureandotherConstructionIndustry3%ofBuildingSectorCarbonEMBODIEDOPERATIONALResidential(Direct)Residential(Indirect)Non-Residential(Direct)Non-Residential(Indirect)EstimatedEmissionsforBricksandGlassBuildingConstructionIndustryConcrete,Aluminium,Steel7BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREThechoiceofmaterialsimpactseveryaspectofabuilding’slife-cyclecarbonemissions.Thechoiceofconstructionmaterialsimpactseveryaspectofabuilding’slife-cycleemissions.Materialselectionhasahugeimpactonoperationalemissionsbecauseofthewayitaffectsenergydemand.Materialchoicescanliterally“changethe(micro)climate”bycontributingtotheurbanheatislandeffect(Narumi,LevinsonandShimoda2021,seeFigure2.4).Amaterialcaneitherabsorbtheheatfromthesun(aswithconcreteandbrick),reflectsolarheatgain(aswithlight-colouredsurfaces)ortransformsolarenergy(throughon-sitepowergenerationand/orlivingmaterialssuchasgreenroofs).Theuseofheat-absorbentmaterialssuchasconcreteincreasesurbantemperaturesandtheenergydemandforcoolinginbuildingsusingmechanicalair-conditioning(DavisandGertler2015;Deroubaixetal.2021).Impervioussurfacessuchasconcretealsocauseexcesswaterrun-offandaddtothecarboncostsofpumpingandtreatingstormwater.Incertainclimates,whendesignedproperly,high-massmaterialswithinbuildingscouldsupportpassivethermaleffectsandreducerequirementsforheatingand/orcooling(Pérez-Lombard,OrtizandPout2008).Giventhehugeimpactsthatbuildingmaterialssuchasconcretehaveonbothembodiedandoperationalenergy,themanagementofbuildingmaterialprocessesaccountsfornearlyone-fifthofglobalembodiedcarbonemissions,acrosstheentirelifecycle(OECD2019).2.2EmbodiedEmissionsfromExtractingandProducingBuildingMaterialsTheshareofemissionsfromproducingbuildingmaterialsgrewfrom15%in1995to23%in2015.Despiteitsmassivecontributiontoclimatechange,theembodiedcarbonwithinmaterialshasbeenunder-addressedindecarbonisationstrategies.In2020,theInternationalResourcePanel(IRP)highlightedtheenormouspotentialtoreduceemissionsthroughstrategiesthatincreasetheefficiencyofmaterialuseinresidentialbuildings.IntheG7countriesaswellasChina,strategiessuchastheuseofrecycledmaterialscouldreduceemissionsinthematerialcycleofresidentialbuildingsby80to100percentby2050(IRP2020).InIndia,thereductionscouldreach50-70percent(IRP2020).2.3EmbodiedandoperationalcarbonemissionsoverthebuildinglifespanOperationalcarbonwillcontinuetodecreasewithgriddecarbonisation,whileembodiedcarbonissettoremainhighwithoutmeaningfulaction.AdaptedfromCarbonLeadershipForum2020.Annualemissions(kgCo2e/m2/year)ProjectedImpactofEmbodiedCarbonRelativetoOperationalCarbon2020-2050EmbodiedCarbonScenario1:StandardPerformanceBuildingScenario2:High-PerformanceBuilding202020302040205020302050Upfrontembodiedcarbon(product+construction)Operationalcarbondecreasesasgriddecarbonizesby2050AnnualoperationalcarbonEmbodiedcarbonfromrenovation/maintenance(~15yrs)00100200300400123456789101112131415161718192021222324252627282930318BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE2.4ImpactofmaterialselectiononurbansurfacetemperaturesandtheurbanheatislandeffectBuildingmaterialsliterally“changetheclimate”andaredirectlyresponsibleforrisingtemperaturesinurbanareas.Acomparisonofthesurfacetemperaturesfromconventionalroofmaterialsversusgreenroofs,indicatingdarkpurple(coolest),andyellow(hottest)roofs,showingthatvegetatedsurfacessignificantlydecreasetemperaturescomparedtoasphalt.Source:U.S.EnvironmentalProtectionAgency2017.Theproductionphaseofbuildingmaterialsisthemaincontributortoembodiedcarboninbuildings.Withthesurgingdemandformaterials,theshareofgreenhousegasemissionsfromproducingbuildingmaterialsgrewfrom15percentin1995to23percentin2015(IRP2020).Histori-cally,smallerbuildingsweremadewithlocal,lower-carbonmaterials(suchasearthmasonry),buttheseareincreasinglybeingreplacedbylarger,carbon-intensiveconcreteandsteelstructures.Manyofthemostcommonlyusedconstructionmaterialstodayrelyonenergy-intensive,mineral-basedextractiveprocesses,andtheiremissionsaresettoincrease(seeFigure2.5).Inadditiontoclimateimpacts,theseextractiveprocessescanhavedeleterioussocialandenvironmentalimpactsacrossthemateriallifecycle,suchasbiodiversityloss,highwaterconsumption,watercontaminationandriskofforcedlabour.Thecementindustryaccountsfor7%ofglobalCO2emissions.>Theproductionofcementandsteelforconstructionaccountsformorethan11percentofglobalandprocess-relatedcarbonemissions(GlobalABC,IEAandUNEP2019).>Embodiedemissionsfromtheironandsteelindustrycomprisearound7percentofglobalgreenhousegasemissionsand11percentofglobalcarbondioxide(CO2)emissions(Hasanbeigi2021).>Thecementindustryaccountsforanother7percentofglobalgreenhousegasemissions,generatedduringtheproductionandimplementationofconcretestructures(Hasanbeigi2021;Milleretal.2021).2.3EmbodiedEmissions:FromEnd-of-LifetoRe-UseandRecyclingToreduceembodiedcarbon,retrofittingandre-usingbuildingsispreferabletodemolitionandbuildingnew.Atthe“end-of-life”phaseofbuildings,anymaterialsthatarenotrecycledcontributesubstantiallytorapidlygrowingwasteproduction.Toavoidthiswastechallenge–aswellastheneedtoextract,processandtransportnewrawmaterials–retrofitting(toimproveenergyefficiency)andre-usingbuildingscanbepreferabletodemolitionandbuildingnew.Thelongerabuildinganditselementslast,thelessembodiedcarbonisexpended(HistoricEngland2019).Theaveragelife-timeofbuildingsofalltypescurrentlyrangesfromaround30yearsinChinaandIndia(Liu,BangsandMüller2013;Pauliuketal.2013;Hongetal.2016)to80yearsintheUnitedStatesofAmerica(Mülleretal.2006;Kapuretal.2008).Extendingbuildinglifetimeswouldcreatesignificantopportunitiestoreduceaggregateembodiedcarbon.Inthecirculareconomy,thematerialwastefrombuildingsis“designedout”.Appliedtothebuiltenvironmentsector,theso-calledcirculareconomyenvisionsafuturewherethematerialwasterelatedtobuildingsis“designedout.”Thisisachievedbykeeping9BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREconstructionmaterialsinuseandextendingthelifeofabuil-dingforaslongaspossible(Haasetal.2015).There-useandrecoveryofmaterialsisessentialtowardsachievingcircularproductionanduseofbuildingmaterials.Themostcarbonsavingsatabuilding’send-of-lifecomesfromre-use:there-useofabuilding,thenreusingcomponents,thenreusingmaterials.Bycomparison,recyclingandreprocessingofmaterialshavelowerdecarbonisationbenefits.Anotherpathtowardscircularityisimprovingtheefficiencyofmaterialstoenablebetteroperatingperformanceofbuildings(seechapter3).2.4ImplementingaWholeLife-CycleApproachtoBuildingMaterialsAwholelife-cycleapproachisnecessarytoenablemulti-stakeholderengagementandcross-industrycooperation.Thebuiltenvironmentprocessinvolvesenergy,materialandinformationflowsateachofitslife-cyclephases,frominitialmaterialextractiontofinaldismantling.Thetypicalapproachtothedesignandconstructionofbuildingsislinear,whereateachphaseofthelifecycletheembodiedcarbonofabuildingaccumulates.Thisincreaseinembodiedcarbonresultsfromtheuseofenergyandmaterialsto:1)sourceandextractbuildingmaterials,2)manufacturethematerials,3)constructthebuildingstructurefromthematerials,and4)maintainthebuildingduringitsservicelife.Hence,witheachlife-cyclephasetheretypicallyisacarboninvestment.Althoughtherearenowagreeduponstandardsforreportingemissions(seeFigure2.6),itisoftenverydifficulttoaccu-ratleyestimatecarbonfootpinrtsduetotheinsufficientdataand/orknowledgeofallcontributingfactors,whicharecomplex,includingnaturalones.Therefore,thereisstillmuchdevelopmentthatneedstotakeplaceintoolsandmethodstosupporttheproductionofreliabledataacrosstheboard.Increasingly,industryleadersarepromotingafundamentalshifttowardsacircular,“wholelife-cycle”approachtoguidestrategiestoreduceboththeembodiedandoperationalcarbonassociatedwithbuildingmaterials.(Seetoolsinchapter6.)Awholelife-cycleapproachisverydifferentfromalinearapproach.Itrequiresstakeholderstocooperatetowardsconsiderationoftheenvironmentalimpactsofmaterialchoicesbeforethematerialsareevenextracted,andthenateachsubsequentphaseofthebuildinglifecycle.Thismeansthinkingaboutnotjusthowbuildingsareconstructed,butalsohowthechoiceofmaterialsaffectstheamountofheatingorcoolingneeded,andhow,attheendoftheiruse,thesematerialscanprovidea“bank”ofresourcestothenbere-usedforanotherbuilding’slifecycle.Lookingatthebuildingprocessfromawholelife-cyclepointofviewmeansconsideringallthecarboncostsofmaterialchoices,fromtheimpactofmaterialextractiononecosystemstotheenvironmentaleffectsofproduction,construction,maintenanceanddemolition(seeFigure2.7).“Wholelife-cycleemissions”areacombinedmeasureoftheembodiedemissionsinbuildingmaterialsandtheoperationalemissionsfromabuilding’senergyuseandenergy-sourceemissions(Magwoodetal.2021).Bymakingassessmentsanddecisionsaboutcarbonimpactsoverthecourseoftheentirebuildinglifecycle,wecanallowforchoicesthatoptimiseforcarbonefficiencybetweenbothembodiedandoperationalcarbon.Thewholelife-cycleapproachsupportsthedeploymentofacirculareconomybyenablingcooperationacrossstakeholders.Thewholelife-cycleapproachsupportsthedeploymentofacirculareconomybyenablingcooperationacrossstakehol-ders.Ifanewbuilding’smaterialscanbesourcedfromrecy-cledmaterialsatthebeginningofitslife–or,conversely,ifabuilding’smaterialscanberecycledattheendofitslife–thiswillmitigateitsembodiedemissionsandthusitstotalemis-sionsoveritslifespan.Themainstrategiesfordecarbonisa-tionacrossabuilding’slifecycle–fromdesigntooperationstoend-of-use–mustinter-relateforprimeoptimisation.Thekeytoachievingwholelife-cyclethinkingistoensurethattherightdecisionsaremadeearlyinthedesignprocesstodeterminethecarbonimpactoverabuilding’slifespanand2.5Projectedgreenhousegasemissionsfrombuildingmaterialsinabusiness-as-usualscenarioto2060Emissionsfromconcrete,steel,brick,aluminium,glass,woodandcopperareallsettoincreasesubstantially.Source:Zhongetal.2021.WoodGlass54321202020302040205020600greenhousegasemissions(GigatonCO2eq)ConcreteBrickAluminumCopperSteel10BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREFigure2.6Scope1,2,and3carbonaccountingforamaterialproductCarbonaccountingforamaterialproductconsidersScope1,2,and3emissions.Scope1emissionsfromthedirectproductionofgoodsandservices,Scope2emissionsfromtheenergyusedforproduction,andScope3fromindirectcosts,upstreamanddownstreamemissions.Source:Adaptedfrom"LifecycleanalysisandGHGcarbonaccounting,"Pons,2022.ENERGYSUPPLYCHAINEMISSIONSUPSTREAMMATERIALSUPPLYCHAINEMISSIONSPRODUCTIONEMISSIONSDOWNSTREAMEMISSIONSUSEPHASEENDOFLIFEPHASEFossilFuelEnergyOn-SiteManufactureExtractionOff-SiteManufactureOn-SiteDistributionBusinessTravelOff-SitePre-fabricationEmployeeCommutingTransportationandDistributionFurtherManufactureofProductsUrban-ScaleImpactsApplianceandPlugLoadsDisposalEnergyforHeating,CoolingandVentilationRenewableEnergyLIFECYCLEANALYSISMETRICSGlobalwarmingpotential‘[kgCO2e]Humantoxicity[kg1,4-DCBorDALY]Particulates[kgPM2.5]Smog[C2H4ethylene]Ozonedepletion[kgCFC-11]Terrestrialecotoxicity’[kg1,4-DCB]Eutrophication[kgPO]Marineecotoxicity[1,4-Dichlorobenzene]soleimpactcatergoryforGHGprotocolsCRADLETOGATE-BUILDINGPRODUCTCRADLECRADLETOGATE-MATERIALCRADLETOGATE-ASSEMBLEDBUILDINGCRADLETOGRAVEConsumablesandmaintenanceElectricalEnergyEnergylossesinproductionEnergyconsumptionRecyclecreditsCarbonoffsettingbypurchaseorfreeallocationSCOPE2ElecrticityproducedonbehalfofanorganizationGHGCARBONACCOUNTINGDIRECTINDIRECTManufacturingwasteSCOPE3ASupplier’semissionstoproduceextractrawmaterials,produceinputmaterials,energylossesinproductionSCOPE3DEmissionsfromdownstreamoperationsrelatedtosoldgoodsandservicesSCOPE3EPrivateindividual(enduser)emissionsSCOPE3BElectricalenergylossesSCOPE1DIRECTemissionsfromproductionSCOPE3CINDIRECTemissionsfromtransportofﬁnishedgoods,businesstravel,employeecommuting,productionwasteTHEFIRSTSTEPWASDEVELOPINGASYSTEMFORCOUNTINGCARBONEMISSIONSNEXTWENEEDGLOBALCOOPERATIONTOWARDSVERIFIABLEDATAALONGTHESUPPLYCHAINS11BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREend-of-life(seechapter3).Thisistruenotonlyatthebuildingscalebutalsoatthedistrictlevel:materialchoicesinurbandesignaffectthewiderecosystemswithwhichabuildingwillinterface(fromlandandwaterqualitytotheelectricgrid),aswellastheirrelativeimpacts.Wholelife-cyclethinkingrequiresbeingsensitivetothecontext,includinglocalculturesandclimates.Althoughasubstantialshifttolow-carbonbuildingmaterials–suchasrecycledandearth-andbio-basedmaterials–istechno-logicallypossible,itmaybesociallyhardtoimplement,asmanyregionsconsiderconcreteandsteeltobethe“modern”materialsofchoice.Suchashifthastremendouspotentialduetogrowingexperiencewithengineeredtimberandbambooassubstitutesforsteelandconcrete,andtheabilitytousecomponentsderivedfromforestry,agricultureandbiomassby-products.Yetnoneoftheseimprovementscanscaleimpactfullywithoutinnovationandwholelife-cyclecoordinationacrossproducers,designers,buildersandcommunities.2.5TheWholeLife-CycleApproach:PathwaysforDecision-MakersAssessingthecarboncostsofbuiltenvironmentsystemsmustincludemeasuringtheimpactsontheproductivecapacityofglobalecosystems.Globally,strategiesfordecarbonizingbuildingswilldiffergreatlybyregiondependingonlocalnaturalresourcesandthebuildingstock,aswellasonprojectedneedsforthefuture.Patternsinmaterialflowscenariossuggestthatindevelopedcountries,thepriorityistorenovatetheexistingandageingbuildingstock,whilerepurposingwasteinto“materialbanks.”Indevelopingcountries,rapidurbanisationmeansafocusonnewconstruction;inthiscontext,thepotentialtotransformeconomiesbydesigningoutwasteintheearlystages–fromthedistricttothebuildingscale–hasgreatpromise.2.7CarbonimpactsofmaterialsacrossthewholebuildinglifecycleTakinga“wholelife-cycle”approachmeansconsideringallthecarboncostsofmaterialchoices.Note:Lookingatthebuildingprocessfromawholelife-cyclepointofviewmeansconsideringalloftheenvironmentalandcarbonimpactsduringabuilding’slifecycle:fromextractiontoend-of-life.AdaptedfromCLF2020.CONSTRUCTIONUSEEND-OF-USEWORKOFTHEGEO-BIOSPHERERawMaterialManagementFossilFuielsForestandAgricultreMangementPRODUCTIONExtractionTransportManufactureTransportOn-siteConstructionEmissionsRepairandRefurbishmentOngoingMaintenanceEnergyforHeating,CoolingandVenitlationUrban-ScaleImpactsApplianceandPlugLoadsDeconstructionRe-Use,Recycle,RedesignIncinerationLandﬁllOPERATIONALEMBODIEDOff-SitePre-fabrication12BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE2.8KeystakeholderswhoseparticipationiscriticaltothedecarbonisationofbuildingsatdifferentlifephasesTheyincludescientists;architecture,engineeringandconstructionfirms;buildingoccupants;andwastemanagementandrecoveryprofessionals.AdaptedfromKeenaandDyson2017;Keenaetal.2023.CONSTRUCTIONUSEEND-OF-USEWORKOFTHEGEO-BIOSPHEREPRODUCTIONCOMMUNITIESSECONDARYPRODUCTIONSPECIALISTSENGINEERINGFIRMSDEVELOPERSEXTRACTION,AGRICULTURE+FORESTRYINDUSTRIESEARTH+ECO-SCIENCEPROFESSIONALSCONSTRUCTIONFIRMS+CONTRACTORSBUILDINGOCCUPANTSWASTEMANAGEMENTSERVICESARCHITECTUREFIRMSRESEARCHPOLICYFINANCEBUILDINGLIFE-CYCLESTAKEHOLDERSCIRCULARITYTRANSITIONINGTOACIRCULARECONOMYREQUIRESINCENTIVESFORNEWMODELSOFCOOPERATIONACROSSTHELIFECYCLE13BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREBecausethereisnoonestrategytodecarbonisematerials,decision-makersmusttakecumulativemeasuresacrossthelifespanofbuildings.Activeparticipationacrossstakehol-dersiscentral–everyonefromearthscienceprofessionals;toarchitecture,engineeringandconstructionfirms;tobuildingoccupantsandcommunities;towastemanagementprofessionals.Accesstocorrectinformationisalsokeyfordata-drivenpolicies,financialinstrumentsandresearchincentivestosupporteachphaseofthebuildingandmateriallifecycle,andforeachstakeholdergroup(seeFigure2.7).2.6StrategiesTowardsaBuildingMaterialsRevolution:“Avoid-Shift-Improve”Todecarbonisebuildingmaterialsby2060,wemusturgentlysupportsolutionsacrossallmajormaterialtypessimultaneously.Thetransitiontosustainable,low-carbonmaterialswillrevolutionisethewayweconstructcities,infrastructureandbuildings.Toachievea40percentreductioninembodiedcarbonby2030–andcompletelydecarbonisebuildingmate-rialsby2060–wemustimmediatelysupportviablesolutionsacrossallthemajormaterialtypessimultaneously.Transitioningtoalow-carbonfuturerequiresavoidingnewrawmaterialextractionofmaterials.Ifbuildingsaredesignedforcirculardisassemblyandreassembly,theytechnicallybecomematerialbanksattheend-of-life.Toreduceembo-diedemissions,non-renewableresourcessuchasconcreteandsteelneedtobeobtainedfromrecycledorreusedsourceswhereverpossible.Thisshouldbecomplementedbyashifttowardsrenewable,bio-basedproductsifpractical.Insum,arevolutioninbuildingmaterialsrequires:1)dramati-callyreducingemissionsfromconventional(non-renewable)buildingmaterials,and2)acceleratinggrowthinalternative(renewable)materials.Basedonthisunderstanding,theactionsneededtoreduceembodiedcarbonacrossthewholelifecycleofbuildingsandconstructioncanbeclusteredintothreemainstrategies,usingthe“Avoid-Shift-Improve”framework(ProgrammeforEnergyEfficiencyinBuildings[PEEB]2021a)(seeFigure2.8):>AVOIDwaste,buildwithlessandimprovecircularitythroughbetterdesignanddecision-making.Thisincludesusingresource-efficientdesign,extendingthelifetimeofbuildings,and“doingmorewithless”throughholisticdesignandcirculareconomystrategiesthatdesignoutcarbonfromthestart.Italsomeansprioritisingtheuseofrecycled,secondaryandreusedmaterials,whichrequiresdesignfordisassemblyandthere-useofbuildingsandcomponents.(Seechapter3.)>SHIFTtorenewable,bio-basedbuildingmaterialstoreducedemandforprimaryextraction.Thisincludesgreateruseofagricultureandforestryby-products.Ratherthanrelyingonvirginforestformaterials,itrequiresusingwoodandtimberharvestedfromlandsthatwereonceusedforagricultureandimplementingsustainablemanagementandafforestationpractices.(Seechapter4.)>IMPROVEconventionalbuildingmaterialshroughdecar-bonisationefforts,includingthroughenergyandmaterialefficiencyandtheuseofrenewableenergyinproduction.Materialsmadefromprimarysourcesshouldbeproducedusingbestavailabletechnologiesandelectrifiedprocesses,andend-of-userecyclingandre-useshouldbeprioritised.(Seechapter4.)Box2.1providesanoverviewofhowdecision-makerscanadoptawholelife-cycleapproachandusethesethreestrate-giestotransitionbuildingmaterialstoalow-carbonfuture.2.9DecarbonisingbuildingsandconstructionthroughtheAvoid-Shift-ImproveapproachAdaptedfromPEEB2021.AVOIDWASTE,BUILDWITHLESSSHIFTTOBIO-BASEDBUILDINGMATERIALSIMPROVECONVENTIONALBUILDINGMATERIALSANDPROCESSESIMPROVEAVOIDSHIFT•SupplyChainsforlocallyavailablematerials•StandardsandCertiﬁcationsforbio-basedmaterials•Mainstreamingofalternativematerials•ProcessInnovationtoreduceCO2•Substitutionwithsecondaryandwastematerials•EnergyEfficiencyofproduction•Decarbonizationofenergysupply•Life-cycleAnalysistoguidedesigndecisions•Resource-EfficientConstructiontosavematerial•LocalValueChainstolowertransportemissions•CircularApproachesofrecyclabilityandre-use14BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREDuetotheintegrationofmanymaterialsinbuildingsystems,itisessentialtosupporteffortstoreducecarbonemissionsacrossallbuildingmaterials.Acrossallclimatetypes,buildingswillcontinuetorelyonabroadrangeofbothconventionalandemergingmaterialstreams.However,movingtowardsalow-carbonfuturerequiresacumulativechangeinhowbuildingmaterialsareusedandsourced,acrossthefullspectrumofmaterials.Itrequiresholisticapplicationofthe“Avoid-Shift-Improve”strategiespromotedinthisreporttopreventoveruseofextractedrawmaterialsandtofacilitatetheshiftfromnon-renewabletorenewableandsecondarysources.Figure2.10showshowtheseactionswouldchangethetypeofbuildingmaterialsusedandtheirsourcing.Aconsistentlyadoptedwholelife-cycleapproachcoupledwiththedecarbonisationofprimaryemitterssuchasconcrete/cementandsteelwoulddrama-ticallyreduceembodiedemissionsacrossnewandexistingbuildings.BOX2.1TRANSITIONINGBUILDINGMATERIALSTOALOW-CARBONFUTURE2.10Transitioningbuildingmaterialstoalow-carbonfutureDecarbonisationrequiresachangeinuseacrossallbuildingmaterials.Source:Ciardullo,ReckandDyson2023.CurrentGHGEmissions:Zhongetal.2021;OECD2022a.Materialmassandrecyclingratesfrom:Miattoetal.2017(cement);Cullen,AllwoodandBambach2012,Reck2022(steel);InternationalAluminiumInstitute[IAI]2020(aluminium);Westbroeketal.2021(glass);Miattoetal.2017,Miattoetal.2022(masonry);DIetal2021,Geyer,JambeckandLaw2017(plastics);FoodandAgricultureOrganisationoftheUnitedNations[FAO]2020(timber).PercentRecycledContent11223CurrentGHGEmissionsofGlobalBuildingMaterials(GtCO2eq)CurrentMassofGlobalBuildingMaterials(1000MT)RecycledSteelPrimarySteelRecycledAluminiumPrimaryAluminiumRecycledMasonryPrimaryMasonryRecycledPlasticsPrimaryPlasticsRecycledGlassPrimaryGlassPrimaryTimberCircularTimberPrimaryBambooCircularBambooForestryBy-productsAgriculturalBy-productsMyceliumLivingBiomassAVOIDWaste,BuildwithLessNon-RenewablesBiobasedIMPROVEConventionalMaterialsSHIFTtoBiobasedMaterialsDesignforDisasemblyConcreteandAlternativeCementitiousMaterialsPrimaryMaterialSecondaryorCircularMaterial<1%recycledcontent<36%recycledcontent<32%<1%12%21%RelativeShareofMaterialUseperNewBuildingDiagrammaticRepresentation20202050206020202060BIO-BASEDNON-RENEWABLESBIO-BASEDNON-RENEWABLES15BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE3Thereareopportunitiesforcirculardesign,recyclingandre-useateachphaseinthebuildinglifecycle.AVOIDWaste,Build(with)LessandImproveCircularity3.1OpportunitiestoreducecarbonateachphaseofthebuildinglifecycleDecarbonisationrequiresachangeinuseacrossallbuildingmaterials.Source:Keena,Rondinel-OviedoandAcevedoDelosRíos2023,adaptedfromAkbarnezhadandXiao2017.3.1CircularDesignToolsandStrategiesforPlanningandDecision-MakingHowwedesignourbuildingsiskeytoachievingacirculareconomy.Acirculareconomyforthebuiltenvironmentisrootedindesignanddecision-making(KeenaandRondinel-Oviedo2022).Designdecision-makingduringeachphaseofabuilding’slifecycleoffersopportunitiestoreduceembodiedcarbon(seeFigure3.1).Keyinterrelatedcirculardesigntoolsandstrategiesinclude:>upstreamdesignchoices(forexampledecidingonwhattobuild,form,layout,materialsetc.),includingbuilding(with)lessandbuildingsmarter;>selectingbuildingmaterialsandelementsthathavelowerembodiedcarbonbecausetheyareeitherrecycled/re-usedorareinherentlylower-carbon;and>end-of-usestrategiestoavoidwasteandenablethere-useandrecyclingofmaterialsandcomponents.Thesestrategiesmustbeconsideredintandem.Forexample,re-usingmaterialsasmuchaspossibleisagoodstart,butthereisagrowinggapbetweentheavailablesupplyofanddemandforrecycledmaterials(seechapter5).Therefore,anextgoodstepmightbetoreplacehigh-carbonmaterialswithlow-carbonrenewablematerials,suchasbio-basedmaterials.However,itremainsunclearhowthescalingofbiomaterials,suchaswoodandbamboo,willimpacttheabilityofregionalecosystemstosequestercarbon.Bio-basedmaterialsarelowcarbonintheirprocessinganduse,butthismustbeaccom-paniedbysustainableforestryandfarmingpractices(Keena,DuwynandDyson2022)(seechapter4).MATERIALPROCESSINGCOMPONENTMANUFACTURINGMATERIALSOURCINGCONSTRUCTIONOPERATIONEND-OF-USE3.3BuildingLessbyPrioritizingRenovationandUseofExistingBuildings3.5DesignforDissasemblyandModularConstruction3.6Re-useofSecondaryMaterials3.7RecyclingOnlyasaLastResortRecycleMaterialsRe-useMaterialsRe-useComponentsRe-UseBuildingsEMBODIEDCARBONINCREASINGOVERBUILDINGLIFECYCLEPOTENTIALFORDECARBONIZATIONDECREASESTHROUGHCIRCULARECONOMYSTRATEGIES©AliiffYildiriim/Pexels17BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE3.2UpstreamDesignChoicesAreKeytoTacklingCarbonEarlyEarlydesignchoiceshaverepercussionsontheabilitytoreuseorrecyclematerialslateron.Thepotentialtoreduceandavoidembodiedcarbonisgreatestduringtheearlyplanninganddesignphases(seeFigure3.2)(HMTreasury2013;WorldGreenBuildingCouncil2019;PEEB2021a).Atthisearlyplanningstage,takingawholelife-cycleapproachtoprojectfuturelow-carbonscenariosiskey.Circulardesignstrategiesfocusonhowupstreamdesignchoicesimpactembodiedcarbonthroughoutthelifecycle.Earlydesignchoiceshaverepercussionsontheabilitytoreuseorrecyclematerialslateron3.2OpportunitiestoreducecarbonineachstageofprojectdevelopmentThepotentialtoavoidembodiedcarbonisgreatestduringtheplanninganddesignphases.Source:HMTreasury2013;WorldGreenBuildingCouncil2019.DesigningOutWasteandEmissionsfromtheStartThefirstquestiontoaskiswhetheranythingnewneedstobebuiltatall.Acirculareconomyapproachaimstodesignoutwaste.Thepriorityistokeepmaterialsandbuildingsinuseaslongaspossibleandtoensurethattheyarere-usedratherthanturnedtowaste.Manyopportunitiesexistinbothnewconstructionandrenovationtodesignoutwaste,avoidembodiedcarbonandplanaheadbyincorporatingstrategiesearlierinthelifecycle.Thefirstquestiontoaskiswhetheranythingnewneedstobebuiltatall.Alternativestonewconstructionshouldbeexplored.Forexistingbuildings,circularrenovationandretrofitstrategies,suchasextendingthelifeofthebuilding,coupledwithadvancedrecoveryandrecycling,arekeytoachievinglow-carbonoutcomes.Wherenewconstructionisanecessity,designsshouldaimtomaximisebuildinglifespansandtopromoteresourceandmaterialefficiency,therebyreducingtheembodiedcarbonexpended.Duringthisearlyphase,embodiedcarbonemissionscanbeavoidedbyeliminatingnewmaterials,suchasbyincreasingtheuseofexistingassetsandpromotingadaptivere-use.Importantly,upstreamdesignchoiceshaverepercussionsforpotentialend-of-lifestrategies.Theseincludechoicesaboutbuildingmorphology,materialselection,andconstructionassemblies(whichaffectbothembodiedandoperationalemis-sions)aswellasthepotentialfordisassemblyatend-of-life.Consideringtheend-of-lifeduringtheseearlyphasescanresultintheavoidanceofwasteandassociatedcarbonemissionslaterinthebuildinglife.Thisunderscorestheimportanceofusingevidence-baseddecision-makingintheselectionofmaterials,withregardtoembodiedemissions,inthisphase.Onekeywaytopromoteevidence-baseddesignisbyenactingperformance-basedbuildingstandardsandundertakingregulatoryreformstoallowforperformance-basedratherthanprescriptivestandards,toenabletheuseofalternativelow-carbonmaterialsandconstructiontechniques.(Seechapter6formoreontools.)CircularityStrategiesAreContextSpecificOnthepathtowardsdecarbonisation,differentdecisionswillneedtobemadedependingonwhetherthereisaneedfornewconstruction,orforrenovatingexistingbuildings.Newconstructionandrenovationarehappeningglobally(UNEPandIEA2017).However,ifthecurrentlinearapproachtorenovationandnewbuildingconstructioncontinues,itwillexacerbateclimatechange.Decarbonisationstrategieswilldifferbyregionbecauseofvariationsintheavailablebuildingstock.Materialflowscena-riossuggestthatindevelopedcountries,thepriorityistorenovateexistingandageingbuildingstockandtorepurposewasteintomaterial“banks.”Indevelopingcountries,rapidurbanisationmeansafocusonnewconstruction;inthiscontext,designingoutwasteintheearlystagesispromising.However,inbothcontexts,designingbuildingsthatareeasilyreused,repairedorrecycledattheirend-of-lifeisvitalifwearetoshiftfromalineartoacirculareconomy.BuildnothingExplorealternativesBuildlessPlanning0%100%CarbonReductionPotentialDesignConstructionOperationandMaintenanceMaximizeuseofexistingassetsBuildefficientlyProjectDevelopmentStagesUselow-carbonconstructiontechnologiesandeliminatewasteBuildcleverOptimizematerialstageanddesignwithlow-carbonmaterials18BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE3.3BuildingLessbyPrioritisingRenova-tionandUseofExistingBuildingsInacirculareconomy,extendingabuilding’slifeisthemostvaluableandleastwastefuloption.Thebestwaytoreducetheembodiedemissionsofbuildingmaterialsistoavoidmajornewconstruction.Inacirculareconomy,wherewasteisavoided,extendingabuilding’slifeisthemostvaluableandleastwastefuloption,whereasdowncyclingistheleastvaluableoption(Figure3.1).Thus,plannersshouldfavourtherefurbishmentandupgradingofexistingbuildings–usingreusedmaterialswhenpossible–toreducetheneedfornon-renewablematerialextraction.Thelifetimesofbuildingscanbeextendedbyincentivizingrenovationsandretrofitsoverdemolition.RenovationWillSkyrocketintheComingDecadesandCanResultinMuchLowerEmissionsRenovationsgeneratearound50-75%feweremissionsthannewconstruction.Inthecomingdecades,largenumbersofexistingbuildingswillrequirerepairsandreparations.By2030,thereisexpectedtobeasharpincreaseinthenumberofconcretestructuresbecomingoverburdenedandinneedofbuildingsystemrepairs(suchasstructureandfinishing)(Vilches,Garcia-MartinezandSanchez-Montañes2017).Thevalueoftheglobalconcreterestorationmarketissettoincreaseatacompoundannualgrowthrateofaround6percentby2030,toreachnearly$26.4million(ibid.).ThisgrowthisprojectedtobegreatestinNorthAmerica,wheremanymid-centurystructuresareexperiencingprematuredeteriorationduemainlytopoorbuildingquality,improperdesignandafailuretomaketimelyrepairs.Decisionsatanearlyphasetouselessmaterialsbyre-usingbuildingsortheircomponents–especiallyretainingfounda-tionsandstructuralsystems–resultsinavoideddemolitionandwaste,andlessembodiedcarbon.Renovatingexistingbuil-dingsgeneratesaround50-75percentfewergreenhousegasemissionsthannewconstruction,becauseittypicallyinvolvesre-usingthebuildingstructureandenvelope,whichmakeupmostofabuilding’scarbon-intensiveprocessesandmaterials(e.g.,concrete,brick,steelandaluminium)(Strain2017).>PrioritisetheUseofLow-CarbonMaterialsinRetrofitsTheselectionofmaterialsandsystemsiscriticaltowardscreatingalow-carbonbuilding.Engineeredbio-basedmate-rials,suchascross-laminatedtimberandbamboo,offerthepotentialtoreplaceconcreteandsteelcomponents,parti-cularlyforthewidespreadre-purposingofoldercommercialbuildings,wherenewfloorsareaddedtosupplementhousingunits.Swappingaconcrete-basedexteriorwallsystemwithabio-basedstructuresuchastimberorbamboocouldgreatlyreduceboththeupfrontembodiedcarbonandtheongoingoperationalemissionsassociatedwithheatingandcoolingsystems.Carbonemissionsfromrenovationscanbefurtherreducedbyavoidingthereplacementofhigh-carbonmaterialssuchascarpetingandceilingtiles,andinsteadsimplypolishingthesub-flooringandceilingstructureastheinteriorfinish.>RepurposeWastetoNewFunctionsOn-siteorNearbyRepurposingwastematerialsintonewfunctionson-siteorfornearbyusecansavecarbon.Extendingthelifespansofexistingbuildingsandre-usingexistingcomponentshelpstoavoidthelossof“waste”mate-rialstolandfills.Becauserenovationprojectsareundertakenatthebuildingsite,whenoldermaterialsaretornouttheycangenerateupto20-30timesasmuchon-sitewasteasnewconstruction(Strain2017).Therefore,carbonsavingscanbeachievedbyrepurposingwastematerialsintonewfunctionson-siteorforuseinnearbyconstructioninanotherbuildinglifecycle.Thesemethodsarealreadywidespreadininformalandsemi-formalhousingthroughouttheworld,andmuchcouldbelearnedfromthosepracticesfortheformalsectoraswell.>PrioritiseSocio-culturalConnectionstoBuildingstoIncentiviseTheirContinuedUseBuildingsthatlastareonesthatpeopleareperso-nallyattachedto.Thelifespanofbuildingsandinfrastructureisnotdeter-minedsolelybyphysicaldurability,butalsobysocial,culturalandeconomicfactors(Caoetal.2021).Buildingsthatlastareonesthatpeoplearepersonallyattachedto.EmotionalandculturalfactorscanincentivisepropertyownersandCIRCULARCONSTRUCTION©WhiteArkitekter,Martinsons/JonasWestling19BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREespeciallythird-partydeveloperstochoosedurablemate-rialsoverthosewiththelowestinitialcost.Materialsarefundamentalinestablishingdurablevalueovertime,andtheimpactthatmaterialshaveonoccupants’connectiontoaplacetranscendsmerefunctionaluse.3.4FocusingonEnd-of-Use,NotEnd-of-Life,toAvoidLandfillTransitioningfromend-of-lifetoend-of-usepromotesacirculareconomyapproach.Traditionally,end-of-lifeisthephaseofaproduct’slifecyclewheretheendtreatmentorwastemanagementoccurs.Itisthefinalphaseinthelineareconomyof“take,make,waste.”Threepotentialend-of-lifestrategiesfordealingwithabuil-ding’smaterialsandcomponentsincludelandfill,selectivedeconstructionandrecycling.AvoidingLandfillandEmbracingMaterialReuseAttheend-of-lifeofbuildings,themostcommonwastemanagementstrategyisdemolitionfollowedbydisposalofmaterialsinalandfill.However,thisresultsinalossoftheinvestedcarbonaccumulatedoverthebuilding’slifespan,aswellasinadditionalcarbonemissionsfromdemolition,transportandthelandfillitself(AkbarnezhadandXiao2017;DiMaria,EyckmansandVanAcker2018).Oftheroughly100billiontonsofconstruction,renovationanddemolitionwastegeneratedannually,around35percentissenttolandfillonaverage(Chen,Fengetal.2022)(seeAnnex1).Diversionandinnovativemanagementcangreatlyreducewaste(Iyer-RanigaandHuovila2020).Forexample,muchofthisdisposedmaterialcouldinsteadberecuperatedandrecycled,turningdemolitionsitesintomaterialbanksfornewbuildings.However,greaterresearchanddevelopmentintodesigningrecyclablecomponentsneedstobesupported,andbuildingcodesneedtorequirecompliance.Atransitiontoacirculareconomywarrantstransitioningfroman“end-of-life”perspectiveto“end-of-use.”Attheend-of-usestage,thereisthepotentialtopreserve(orstore)theinvestedembodiedcarboninafuturehousingcycle.Acirculareconomystrivestoimproveresourceefficiency,primarilybyclosingtheresourceloop(Haasetal.2015).Withinthebuildingsector,thisinvolvesreducingtheuseofvirginrawmaterialsatthemanufacturingphaseandsubsti-tutingitwithsecondarymaterialsthatareintheirsecondorthirdlifecycle–and,consequently,eliminatingwasteattheend-of-usephase.SelectiveDeconstructiontoAvoidEmbodiedEmissionsSelectivedeconstructioninvolvesdismantlingabuildingratherthandemolishingit.Apotentiallylower-carbonapproachtotheend-of-useofabuildingisselectivedeconstruction,whichinvolvesdismant-lingthestructureratherthandemolishingit.Practicesofre-use,repairandrecyclingallowforretainingthevalueofthebuildingcomponentsandmaterials.Researchindicatesthatselectivedeconstructioncanofferlargecarbonsavingsoverlandfill.InastudyinBelgium,itledtoa59percentdecreaseingreenhousegasemissionspercapitacomparedtolandfill,whereasimplementingrecyclinganddowncyclingpracticesaloneledtoa36percentdecreaseinemissions(DiMaria,EyckmansandVanAcker2018).Similarly,astudycomparingtwoverydifferenthousingsectorsglobally–inLima,PeruandMontréal,Canada–foundthatavoidingwastebydivertingconstruction,renovationanddemolitionmaterialsfromlandfillcangreatlyreduceemissions.Thestudyfoundthataselectivedeconstructionapproachofre-useandrecyclinghadthegreatestdecarbo-nisationpotentialcomparedtolandfill,leadingtoemissionreductionsof70percentinLimaand63percentinMontréal(seeBox3.1).©Maciejbledowski/Envato©HildaWeges/GettyImagesBUSINESSASUSUALFUTURECIRCULARITY20BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURERe-useandrecyclingstrategiescanreduceemissionsinresidentialconstructionbyupto70%.Circularend-of-usestrategiescanreducethelife-cyclegreenhousegasemissionsassociatedwithresidentialbuildingsinLima,Peruby70percentandinMontréal,Canadaby63percent.Thesestrategiescould:1)reducethedemandforvirginconstructionmaterials;2)makesecondarymaterialsavailable,therebyreducingtheneedtoproducevirginmaterials;and3)increasethere-useofmaterialsviaselectivedeconstructiontoreducetheemissionsfromdemolitionandlandfill.BuildingmaterialuseinLima:ahousingboomwithgrowingrelianceonimportsofhigh-carbonmaterialsInPeru,1.8millionhomesareduetobebuiltby2030(NationalStatisticsandInformationTechnologyInstitute2017).Themainconstructionmaterialsusedformulti-familyhousingprojectsinLima,asof2019,areshowninFigure3.3,withconcretebeingdominant(PeruvianChamberofConstruction2020).Althoughmanymaterialsaremanufacturedlocally,thereisatrendBOX3.1LIMAANDMONTRÉAL:UNDERSTANDINGTHEDECARBONISATIONPOTENTIALOFCIRCULAREND-OF-USESTRATEGIEStowardsimportinghigh-embodied-carbonrawmaterials.Thisincludes51percentofsteelscrap(MinistryofForeignTradeandTourism2018);100percentofaluminiumandfloatedglass(Lopez2022);and4.7percentofcement(Vázquez-Rowetal.2019).Upto82percentofbuildingconstructionwasteinLimaisdumpedatinformal,illegalsites(Rondinel-Oviedo2021),withminimalrecycling.BuildingmaterialuseinMontréal:RisingdemandforrenovationsandalargeshareofconstructionwasteIn2021,StatisticsCanadareportedthat59percentofhomeownersinMontréalplannedahomerenovation.Apartmentsmakeup58percentofthecity’sdwellings,withbuildingsoflessthanfivestoreysbeingthemostcommon(StatisticsCanada2017;StatisticsCanada2019).ThematerialbreakdownofMontréal’slow-riseapartmentsisshowninFigure3.3(Keena,Rondinel-OviedoandDemaël2022).AcrossCanada,construction,renovationanddemolitionwasterepresents20-30percentofallsolidwaste(Yeheyisetal.2013).3.3RepresentativehousinginLimaandMontréalandtypicalmaterialsused,bymassandvolume,2019WhereasconcretedominatesinLima’sbuildings,materialuseinMontréalismorediverse.Source:Keenaetal.2023.Others0.15%Others0.78%Others0.60%Others0.15%88.4%8.2%89.8%5.9%3.2%24.5%49.9%30.5%6%5%20.1%15.8%14%9.5%8%6%RepresentativemodelVOLUME(m³)RepresentativemodelLIMAPeruMONTRÉALCanadaVOLUME(m³)MASS(kg)MASS(kg)ConcreteBrickBrickveneerReinforcedsteelGypsumWoodPlywoodInsulationbattInsulationXPSAluminiumTileﬁnishGlassPaintAsphaltrooﬁngshingleEpoxideresinSteelrailingPolyurethanePolyetheleneHighDensityFiberboardx4x421BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE3.4Carbonimpactsofdifferentend-of-usestrategiesinLimaandMontréalRe-useandrecyclinghadthegreatestpotentialfordecarbonisinghousing,comparedtolandfill.Note:Scenario1(S1)=SelectiveDeconstruction(Lima:84%re-use,15%recycle;Montréal:77%re-use,21%recycle),Scenario2(S2)=Recycling(Lima:96%recycling,Montréal:94%recycling),andScenario3(S3)=100%Landfill.Thelegendshowsassumptionsonthelevelsofre-useandrecyclingviability.Source:Keenaetal.2023Thepotentialofend-of-usestrategiestoreduceemissionsfromresidentialbuildingsMaterialmanagementstrategiesemployedattheend-of-usephaseofbuildingsofferopportunitiesforcarbonsavings.Basedonrepresentativehousingmodels(seeFigure3.3),arecentstudyfocusedonthreespecificend-of-usestrategiesforLimaandMontréal:>1—SelectiveDeconstruction,dominatedbyre-usebutalsoincludingrecycling>2—100%Recycling>3—100%LandfillThestudyfoundthatselectivedeconstruction(re-useandrecycling)hadthegreatestdecarbonisationpotential,leadingtoreductionsingreenhousegasemissionsof70percentinLimaand63percentinMontréal,comparedtolandfill(seeFigure3.4).Meanwhile,recyclingalonereducedemissions50percentinLimaand48percentinMontréal.Thisillustratesthatcircularend-of-usestrategiesofmaterialreuseandrecyclingofferamuchlower-carbonapproach.Theemissiondeclinesareduemainlytotheavoidanceoflandfillandtotherecoveryofmaterialforreuse.Re-useandrecyclingleadtoareductionintheprimaryenergyandrawmaterialsneededtoprocessvirginmaterialsintonewmaterialsduringthemanufacturingphase.MONTRÉALCanadaLIMAPeruModelAssumptionsforEnd-of-UseStrategiesLEGENDConcreteBrickGlassGypsumPlywoodWoodAluminiumHighDensityFiberboardPaintPolyurethaneEpoxideresinTileﬁnishInsulationbattTechnologicalviabilityandrecyclingoutputSimpletodivertHighvalueComplextodivertLimitedoptionsSteelrailingInsulationXPSPolyethylene2000010000500015000250003500030000ReusabilitypercentageRecyclabilitypercentageReinforcedsteelAsphaltshinglekgCO2-eq-10000.50.250.75010.50.250.7501S1S2S3SelectiveDeconstructionRecyclingLandﬁllS1S2S3SelectiveDeconstructionRecyclingLandﬁll70%CO2eqsavingsthroughre-useandrecycling50%CO2eqsavingsthroughrecycling48%CO2eqsavingsthroughrecycling63%CO2eqsavingsthroughre-useandrecycling22BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE3.5DesignforDisassemblyandModularConstructionFacilitatingFutureMaterialandComponentRecoveryDesign-for-disassemblystrategiescanresultin10-50%reductionsinlife-cycleimpacts.“Designfordisassembly”andmodularconstructionfacilitateselectivedeconstruction.Thesemethodscanextendthelongevityofbuildingcomponentsandenabledismantlingattheend-of-use.Becausethevalueofthesebuildingelementsisretained,theycaneasilybereused(KeenaandDyson2020).Studiesshowthatdesign-for-disassemblystrategiescanalsoresultin10-50percentreductionsingreenhousegasemissionscomparedtoconventionalconstruction(Keenaetal.2022).However,challengescanariseinearthquake-proneregions,wheresecurebuildingjointsareneeded.Toovercomesuchchallenges,governmentscansupportresearchfornewdesign-for-disassemblysystemsandrecoverymethods,suchasthere-useofreinforcedconcreteasastructuralelementwiththeneedtoaddressseismicresistance.DigitalizationtoSupportDesignforDisassemblyDigitalizationtosupportprefabricationandmodularconstructioncanreducewasteby23-100%.Digitalisation–suchasthree-dimensionalbuildinginfor-mationmodeltechnologies–canhelpwiththedesignandfabricationofthecomplexconnectingcomponentsrequiredindesignfordisassembly.Itcanalsohelpminimisematerialwasteduringconstructionbyresolvingissuesbeforemate-rialslandataworksite.Digitalisationtosupportprefabrica-tionandmodularconstructionhasbeenproventoreducewasteby23-100percent(Jaillon,PoonandChiang2009;LuandYuan2013;Chen,Msigwaetal.2022).Buildinginformationmodellingisadigitalsolutionthatcanbeappliedtoallbuildingtypes.However,forsmallerandless-complexbuildings,itmaybesimplertouseabuildingpassport.Abuildingpassportisawholelife-cyclerepositoryofbuildinginformation–adigitaldescriptionofabuilding.Itcoversabuilding’sadministrativedocumentationaswellasdataregardingitssiteandlocation,itstechnicalandfunctionalcharacteristics,anditsenvironmental,socialandfinancialperformance(GlobalABCandUNEP2021).Buildingpassportscanplayarolebycreatingadatarepositorythattracksmaterialchanges,maintenanceandrepairthathaveoccurredinabuildingovertime.3.6(Re-)UseofSecondaryMaterialsGovernmentincentivescanencouragethere-usemarketplaceandwidespreadadoptionofsecondarymaterials.Secondarymaterialssuchasscraporresidualsfromconstructionprocessesarecurrentlymassivesourcesofwasteandhavegreatpotentialforintegrationintobuildingstructures.Forsecondarymaterialstocompetestronglyintheconstructionmaterialsmarketplace,technical,opera-tional,social,cultural,regulatoryandeconomiclimitationsneedtobeovercome(Knoth,FufaandSeilskjær2022).Poli-cymakingiskeyinhelpingtoovercomelimitationssuchasthelackofaregulatoryframework.Governmentincentivescanencourageboththere-usemarketplaceaswellasthewidespreadadoptionofsecondarymaterialsandselectivedeconstructionpractices.FundingIsNeededtoAddressTechnicalChallengesFromadesignperspective,theweightanddimensionofanelementormaterialcangreatlyinfluenceitsre-usability.Lighterandsmallermaterialsandcomponents,designedwithflexiblejoints,willbemorefeasibletoreuse.Fundingmechanismsareneededtoadvanceresearchanddevelop-menttoovercometechnicallimitationsofre-useandreco-very,suchasmaterialdegradation,seismicandfire-proofspecifications,anddesignfordisassembly.Researchcanalsohelptailorframeworksforre-usetodifferentcontexts.AswasillustratedforLimaandMontréal(seeBox3.1),thecarbonsavingsfromend-of-usestrategiescandifferacrossregionsdependingonthetechnicalspeci-ficities.Inregionswherereinforcedconcreteiscommonlyused,there-useofstructuralelementsislessviable.Forearthquake-proneregions,thedesignofre-usablestruc-turalelementswillneedtoaddresstheseismicresistanceofmaterials.Incontrast,inregionsthatuselightermate-rials,suchaswood,thepotentialforre-usabilityishigher.However,mostsecondarylightweightwoodisnotreusedorrecycledtodaybutisusedmostlyforenergyrecovery(seechapter4).EducationIsRequiredtoIncreaseTechnicalKnowledgeandSocialAcceptanceToincreasetechnicalknowledgeexchangeontheuseofsecondarymaterials,governmentscansupporttraining,educationandresearchonthepracticesandskillsneededtoconductselectivedeconstruction(McClureandBartuska2007;Deplazes2012;Rondinel-OviedoandSchreier-Barreto2019;CruzRiosandGrau2020;Hossainetal.2020).Fromasocio-culturalperspective,specificmessagingalsoneedstobedevelopedtoshiftthemindsetthatsecondarymaterialsareoflesservalue.Instead,itisimportanttoconveythe23BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREnotionthatthesematerialsaredesirableandtosupporttheiracceptanceinthemarketplace.PoliciesCanSupportStandardsforSecondaryMaterialsandIncentiviseMarketsMarketsareneededforre-usableproducts,withspecialisedcontractorsandre-usecentresleadingtonewjobopportunitiesThedevelopmentofassessmentstandardsandcertifica-tionsforsecondarymaterialsiskeyinassuringthesafetyandefficacyofre-usematerials.This,inturn,canhelppromoteselectivedeconstruction.Policiesareneededtodevelopandregulatethegovernmentapprovalprocessformaterialsbeforetheyenterthemarketplace.Forinstance,secondarymaterialsmustmeetrecognisedmaterialstandardsandcertificationregardingtheircompositionandproperties,andmustalsocomplywithbuildingcodes.Secondarymate-rialsmustbeassessedtoensurethattheymeetthesamestandardsasvirginmaterialsinorderforlegallimitationsandsocialacceptancetobeovercome.Economicdriversforre-usecanbeaseffectiveaslegislation(King2021).Financialincentivescansupportthecreationofare-usemarketplace–newenterprisesandspecialiseddeconstructioncontractorsthatallowforthecarefuldismantlingofabuildingandforthestoring,preparationandmaintenanceofsecondarymaterialsforresale.Thisincludesestablishingre-usecentresthatconcentrateend-of-usematerialsina“one-stopshop”(Forrest2021),whereelementswithhighervaluecanberesoldbeforegoingtosortingfaci-lities.Byenablingcirculareconomiesinthebuildingsector,newjobopportunitiescanbeprovided.3.7RecyclingOnlyasaLastResortManyregionshavealackofconfidenceinrecycledproductsandfaceculturalresistance.Inacirculareconomyparadigmof“re-use,repair,recycle,”wherewasteiseliminated,thepracticeofrecyclingordowncyclingbecomesalastresort,asittypicallyresultsinaproductoflesservalue.Althoughdiverserecyclingtechniqueshavebeenwelldevelopedglobally,manyregionshavenotimplementedrecyclingmethodsforconstruction,renovationanddemolitionwasteduetovariouslimitations.Theseinclude:alackofconfidenceandreluctanceinrecy-cledproducts,culturalresistance,lackofcertaintyaroundtheeconomicfeasibilityandviabilityofinvestinginadvancedrecyclingmethods,poorcommunicationandcoordinationamongparties,andinsufficientpoliciesandregulations(Jinetal.2017).Illegaldumpingisalsoanissue,particularlyinmanydevelopingcountries.InthecaseofLima,Peru,importedmaterialswithhighembodiedcarbon,suchassteelandthecementusedforconcrete,makeuparoundthree-quartersofconstruction,renovationanddemolitionwaste(Rondinel-Oviedo2021).Thisiscommonacrossthedevelopingworld.However,muchofthismaterialcouldberecoveredforreuseorrecycling.Studieshaveshownspecificexampleswheregovernmentincentives,awareness,andknowledgetransfer,aswellaslegalandregulatoryframeworksregardingrecoveryofthesematerials,havebeeneffective(Liu,BangsandMüller2013).Recyclingandreusereducetheneedtoimportvirginmate-rialsandalsohelppromotethelocalvaluechain.On-sitesortingandprocessingofmaterialsbenefitre-useandrecyclingenterprisesandmakewastemanagementmoreefficient.Additionally,transferplantsandwell-locatedre-usecentresenablemoreefficienttransportofthesematerials.Theestablishmentofqualitycriteriaforrecycledproductscanenablecertificationofthefinalproduct,therebyincreasingitsmarketacceptance.Digitalisationcansupportwastediversionatthebuildingend-of-lifebymoni-toringandcontrollingmaterialuseandbyprovidingrecyclingcompanieswithadvancenoticeofthetypeandamountofconstruction,renovationanddemolitionmaterialsthatwillbetransportedtothem(seechapter6).3.8CircularStrategiesinNewBuildingstoAvoidEmbodiedEmissionsIncaseswherenewconstructionisrequired,designstrate-giescanbeusedthatreducetheamountofmaterialusedandthatprioritisetheuseoflocallysourced,circularandbio-basedmaterialswithlowembodiedcarbon.Thesemate-rialscanbeusedtobuildlarger-scale,adaptablestructuresthatalignwiththeprinciplesofthecirculareconomy.AdoptingCircularStrategiesintheMaterialManufacturingandDesignPhasesConstructionpracticesbasedon“designfordisas-sembly”canpromoteadaptablestructuresthatmakematerialseasilyrecoverable.Whennewconstructionisnecessary,itcanincorporatecirculardesignstrategiesthatreducetheamountofmaterialused.Decisionsaboutmaterialselection–suchaschoosinglow-carbonmaterials(whetherbio-basedorreclaimed)–willgreatlyavoidtheneedforextractingandusingnon-re-newablevirginrawmaterials.Additionally,constructionpracticesbasedondesignfordisassemblycanpromoteadaptablestructuresthatmakematerialseasilyrecoverableforre-useattheendofabuildinglife.24BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURESUMMARYKEYDESIGNSTRATEGIESTOIMPROVECIRCULARITYINBUILDINGSBuildless,andbuildwithless>Promoteadaptivere-useandconservationofexistingbuildingstoextendtheirlifetime.Fornewbuildings,promotelightweightconstruction,usingfewermaterials,andmandatelongerlifespanestimations.Useperformance-basedbuildingcodes>forembodiedcarbon,whichfacilitateupstreamdesignstrategiestodesignoutwasteandtacklecarbonearly.Performanceratherthanprescriptive-basedbuildingcodeswouldbesupportedbywholelife-cyclethinkingandanalysis.Promoteevidence-basedmaterialselection>andawarenessamongbuildingprofessionalsofalternativelow-carbonconstructionmaterialsandcomponents(bothnewandsecondarymaterials)earlyon,toreducelong-termwaste.Promoteselectivedeconstruction>attheend-of-usephase,prioritisingcarefuldismant-lingoverdemolitiontosupportmaterialrecoveryofbuildingcomponentsandmaterials.Designfordisassemblyandmodularconstruction>Newbuildingsshouldbedesignedfordisassemblyandshouldusemodularconstructiontoenhancelongevityandenabledismantling,therebyreducingexpendedembodiedcarbon.Acceleratedigitalisationofbuildings>tosupportwastediversion.Buildinginformationmodellingand/orbuildingpassportscanbeusedtomonitorandcontrolmaterialuseandtoalertrecyclingcompaniesofincomingend-of-usematerials.Digitalisationcanalsofacilitateassessingthequalityofsecondarymaterialsbeforetheyre-enterthemarketplace.Encouragingdigitalisationintheconstructionprocess,especiallyforinstitutionalandpublicbuildings,willleadtoamarkettransformationandfacilitatetheinclusionofthesetechnologiesinsmallerbuildingssuchashousesPromisingtechnologicaldevelopmentsareemergingforcementsandbindersderivedfromthedirectcaptureofCO2emissionsthataregeneratedatpowerplantsandotherindustrialsmokestacks(Caoetal.2021)(seechapter5).Thedecarbonisationpotentialishuge:iffuturebuildingmaterialswerederivedfromcarboncapture,thenevennewbuildingscouldpotentiallybecarbonnegative.Ifcarbon-in-tensivematerials(concreteormetals)needtobeused,manystrategiesinthematerialprocessinganddesignphasescangreatlyreduceembodiedcarbon:>Designingmoreefficientstructuralsystems(e.g.,stan-dardisationofcomponents,usingmechanicaljointsinsteadofchemicaljoints)foreaseofdisassembly.>Pre-fabricatingcomponentsoff-sitetoavoidwasteandconstructionemissions.Thiscaninvolveusingfacto-ry-controlledmethodsthatoptimisematerialuseandenableacomponenttobedisassembledandreassembledintoafuturelifecycleinsteadofbeingdiscarded.Insomecases,off-siteconstructionhasreportedlyreducedwastebyupto100percent(Chen,Fengetal.2022).>Makingimprovementsduringtheproductionphase,suchaselectrifying(withrenewablesources)asmanyprocessesaspossible,andimprovingthemixturesforconcreteandcement.SelectingLocallySourced,CircularandBio-basedMaterialswithLowEmbodiedCarbonInnovatorsareworkingtoincreasethemarketshareoflowcarbonandbio-basedmaterials.Fortheselectionofnewbuildingmaterials,innovatorsareworkingontwomajorfrontsto:1)reducetheemissionsofconventionalbuildingmaterials(seechapter5),and2)increasethemarketshareofalternativebuildingmaterials,suchasreusedandrecycledmaterialsaswellaslocal,low-carbonsolutionsandbio-basedmaterials(seechapter4).Shiftingfromnon-renewabletocircularmaterialsmayhelpalleviateenvironmentalstressfromdepletingrawmine-ral-basedmaterialsandpromotecircularflowsofagricul-turalandotherwastes(Churkinaetal.2020).(Seechapter4).Advancementsinbio-basedmaterialsystemspresentopportunitiestoexpandtomulti-storyconstruction,inclu-dingadaptablestructuresthatcouldsupportdesignfordisassembly.Thesekindsofstructuresmayofferthepoten-tialtosequestercarbonduringthematerialproduction,constructionandusephases(Johnetal.2009;Robertson,LamandCole2012;Laguarda-Malloetal.2014;Keenaetal.2022).Thesebenefitsofashifttobio-basedmaterialsarediscussedinthenextchapter.254Movingtowardsmorerenewablematerialsrequiressustainableresourcemanagementandincentivizingbiodiversity.SHIFTtoBio-basedBuildingMaterials4.1HistoricaldevelopmentofatmosphericcarbonpatternsAshifttobio-basedbuildingmaterialsby2060canreplenishthecarbonpoolandreduceatmosphericcarbonNote:Thefigureshowsthehistoricaltransitionintheterrestrialcarbonpoolfromformation(left)todepletion(middle)togradualreplenishment(right,withsimultaneousreductioninatmosphericcarbon).AdaptedfromChurkinaetal.2020.4.1ScalingRenewableBuildingMaterials:OpportunitiesandChallengesRenewablebio-basedbuildingmaterialscandrivereductionsinatmosphericcarbon.Ifmanagedresponsibly,renewablebio-basedbuildingmaterialshaveauniquecapacitytodrivereductionsinatmosphericcarbonby:1)matchingrenewableresourcestobuildingmaterialapplications,atlowercarbonfootprints,and2)servingasaglobalcarbonsink(seeFigure4.1).Timberistheleadingbio-basedbuildingmaterialbeingusedatscale.Althoughpromisingtechnologicalproductinnovationsareavailabletoaddressrisingdemandfortimberindevelopedcountries,demandoutpacesforestregrowthandreliesonalimitedrangeoftreespecies(Pomponietal.2020).Globaltimberdemandhasalargeimpactontropicalforests,espe-ciallysincemanytropicalcountriesdonothavesufficientfinancialandinfrastructuralresourcestoimprovematerialefficiencyandsustainableforestmanagement.Morepolicysupportisneededtoencouragetheuseofwastebiomassinbuildingmaterials.Increasedinvestmentisneededtodevelopregenerativemethodsofmanagingglobalforestsandagriculturallands.Thepotentialtoredirectbiomassresiduesintocostcompe-titiveconstructionproductssuchascementitiousbinders,bricks,panelsandstructuralcomponents,couldincentivizemorecarefulandproductivemanagement.Compoundingbenefitsincludethecapacitytostorecarbonwithinbuildingmaterialsandproducts,therebyreducingclimatechangeemissionsfromdecayingmatter,forestfiresandtheburningofcropwaste.Further,majorcarbonsequestrationbenefitscouldcomefromnewcooperativeapproachesbetweenbuildersandforestmanagerstoincreasethebiodiversityofforeststhroughtheselectionoffunctionalattributesforbuildingmaterialsaccordingtospecies(Osborneetal.,2023).Apromisingavenuetoalleviatepressureontimberresourcesisthedevelopmentanduseofreconstitutedwoodproductsfromnon-timberlignocellulosicresiduesfromforestry,agriculturalandfood“waste.”Today,mostofthebiomassfromagriculturalby-productsiseitherabandonedonland(generatinggreenhousegasemissionsthroughnaturaldecomposition)orburned(releasingcarbondirectlytotheatmosphere).Withinforests,excessbiomassresiduescanfeedandexacerbatewildfires(Sahooetal.2021).Meanwhile,inurbanareas,wastebiomassistypicallyeitherlandfilledorcombustedforenergyrecovery,bothofwhicharemorecarbon-intensivepathwaysthanconvertingthiswasteintovaluablebuildingmaterials(Tripathietal.2019;Lan,ZhangandYao2022).Scalingbiomassresiduesfromagriculturerequiresabiodiverseandmaterial-efficientapproachtoavoidworseningthenegativeenvironmentalandlabourimpactsofmonocultureagriculture.350Ma175020202050Mineral-basedconstructionmaterialsAtmosphericcarbonTerrestrialcarbonCarbonpooldepletionCarbonpoolreplenishmentCarbonpoolformationBio-basedconstructionmaterials©SteveProehl/GettyImages27BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE4.2TimberandWoodKEYMESSAGERecentadvancesintimberbuildingmaterialtechnologiesofferthepotentialtoreplacecarbon-intensivesteelandconcretestructuresinsomeurbanareaswithmasstimber.Thisprovidesthedoublebenefitofreducedproductionemissionsandlong-termcarbonstorageinthebuildingcomparedtomineral-basedmaterials.However,itwillbecriticaltoprioritiseappropriateafforestationpractices,particularlyinthenaturalforestregionsoftropicalcountries,whereloggingratesfaroutpaceeffectivereplanting.MassTimberHasGreatPotentialtoReplaceSteelandConcreteandReduceEmissionsSubstitutingconventionalmaterialswithmasstimbercouldreduceglobalemissions14-31percent.Inthelasttwodecades,cross-laminatedtimber–awoodproductmadefromthecrosswiselayeringandlaminationofstructuralgradetimber–hasbecomeanattractivealternativetoconcreteandsteel,duetoitspotentialforscalability,sustainability,strength,andflexibility,aswellasitssuitabilityforincorporationintofast,modularoff-siteconstructiontechniques(MalloandEspinoza2014;Brandneretal.2016).Becausecross-laminatedtimberhasacomparativelyhighstrength-to-massratio,itcanbeusedforwalls,floorsandceilingsinhybridreinforcedconcreteorsteelsystemsinlow-tomid-risebuildings,oneofthefastestgrowingmarketsinemergingeconomies(SchmidtandGriffin2013).Inmanycases,governmentsaremodifyinglawsandnationalcodesthatpreviouslyrestrictedtheuseoftimberconstructionsystemsintallbuildings,tonowpromotetheuseofwood(Umeda2010;Sinclair2019).LocalandregionalstudieshavefoundthatsubstitutionpracticesusingmasstimbercouldreduceglobalCO2emissions14-31percentandglobalfossilfueluse12-19percent(Oliveretal.2014;Pilli,FioreseandGrassi2015).Moreconservativeestimates,however,showlowercarbonstoragepotentialandhighlightthevulnera-bilityofsuchmodelstomarketshocks(JohnstonandRadeloff2019).Masstimberbuildingshavedemonstratedover10percentloweroperationalenergycomparedtosimilarconcretebuildings(Chen2012).Whenaccountingfor55percentrecyclingand45percentenergyrecoveryratesforend-of-lifecross-laminatedtimber(Johnetal.2009),masstimberbuildingshaveshown40percentemissionsavingsandlowerenvironmentalimpacts(Johnetal.2009;Robertson,LamandCole2012;Laguarda-Malloetal.2014).TimberandWood©AlexJones/UnsplashAsmorecountry-specificstudies(particularlyinthedevelopingworld)examinethepotentialoftimberbuildingmaterialstostorecarbonandmitigateclimatechange,thiscaninformregionaldifferencesintheclimatemitigationpotentialofwoodproductsanddevelopincentivesforsustainableforestmanagement..SafeguardsAreNeededtoEnsureSustainableTimberSourcingandAvoidPitfallsForestcertificationandtimbertrackingpracticescouldreducewoodwasteby14-184percent.Timberhasbeenusedasaconstructionmaterialandfordiversebuildingproducts,suchasstructuralbeams,panelisedboards,andwallsandwindowframing.However,increaseddemandforsuchapplicationsrequirestheesta-blishmentandimplementationofsafeguardsthatensureresponsibletimbersourcing.In2020,theglobalwoodharvestcamefromtwomainsources:forestplantations(whichaccountedfor8percentofglobalcropland)andnaturalforestarea(4percentoftheglobaltotal)(Evans2009;Mishraetal.2022).Currently,theoverallrateoftimberharvestinganddefo-restationinnaturalforestsworldwideisfasterthantheoverallregrowthofforests(Pendrilletal.2019;Zhangetal.2020).Timberdemandisrisingbothinemergingeconomies,whichusewoodresourceslargelyforfuel,andindevelopedcountries,whichuseitmainlyforbuildingmaterialsandpaperproducts.Globally,theuseofharvestedindustrialroundwoodforproductssuchaswood-basedpanelsandveneersheetsincreasedsignificantlybetween1960and2018(seeFigure4.2).4.2Globaltrendsinharvestedwoodproducts,1960-2018Useofindustrialroundwoodforwood-basedpanelsandveneersheetshasincreasedsignificantly.AdaptedfromFAOSTATdatafrom1960-2018,inSteeletal.2021.©Katerra1960200400600198020002018GlobalProduction(Mm3)GlobalForestsFuelIndustrialRoundwoodPulpandPaperProductsUsedintheBuildingSectorOtherWood-BasedPanelVeneerSheetSawnwood29BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREAcrossthetimberandbiomassindustries,gendernormsandrelationsplayacriticalroleincomplexresourcemanagementandbiodiversityconservationpractices(Shiva1992;Agarwal2010;KiptotandFranzel2011).Globalpatternsofgendernormslargelyshowthatmenparticipateinandmanageseasonalforestrypracticeslinkedtocashincome,whereaswomenhavebeenresponsibleforthedailyprovisionofforestryresourcesforfoodandbroadhouseholdneedsthatlieoutsideofformallyremuneratedwork(Shiva1992;Agarwal2010).Inthissense,notonlyisthedailymulti-taskingnatureofwomen’slabourlargelyinvisible,butthelikelihoodofexpandingwomen’sparticipationincommerciallyproductiverolesisrestrictedduetotheheavyworkload.Suchnormsarewovendeeplyintothesocialorganisationofagriculturalandindustrialcommunitiesandhavehistoricallynormalisedtheroleofwomenandchildrenasaninformalcommunity“supportworkforce”toserviceaprimarymale-dominatedlabourandmanagementworkforce(Arora-Jonsson2014).Thisparadigmhasledtopolicygapsinvaluingandsupportingforestryextensionservices(YokyingandLambrecht2020;Nara,LengoiboniandZevenbergen2021).Critically,whengovernmentpolicyfocusesprotectionandjobsecuritysolelyonprimarymaleforestryworkers,thisincreasesthedependenceofthewomen-dominatedworkforce,particularlyintermsofeconomicandland-usetransition(Reed2003).Globalstudieshavedocumentedtheroleofwomenintheselection,propagationandmarkingof“wild”plantresources,effectivelyservingasbiodiversitycustodians(Shiva1992;Howard2003a;Howard2003b;KiptotandFranzel2011).InChina,womenfarmershavebeenthedrivingexpertsbehindmaizebreeding(Shiva1992;Song1998;SongandJiggins2003).StudiesinSouthAsiashowthe“snowball”impactofverticalmobilityinfemaleexecutiveleadershippositions,leadingtoincreasedfemaleparticipationintimberresourceco-managementanddecision-making(Agarwal2010).InSweden,whilewomenrepresent2percentoftheconstruc-tionsectorworkforce,anationalstudyfoundthatwomenaccordedhigherinterestandimportancetoenvironmentalissuesbuthadlowerinfluenceonenvironmentaloutcomes(Wallhagen,ErikssonandSörqvist2018).Suchpatternsofferimportantfoundationsfordestigmatizingandincreasingwomen’senvironmentalparticipationandleadershipacrossalllevelsinthebuildingsandconstructionlaboursector.Giventhatwomenfacebarrierstoaccessingcreditandloans,financialinstitutionsneedtoserviceanddesignloancollateralsystemsthataresuitabletoindividualsandwomencollectives(Demirgüç-Kunt,KlapperandSinger2013).Whilefinancialinclusionservesasabasisforbringingwomentothetable,governmentalprogrammesandpoliciesneedtoexpandwomen’saccesstonewtechnologies,marketinginformationandtrainingtosustaintheirparticipationontheground(KiptotandFranzel2011;ColemanandMwangi2013;Agarwal2015).BOX4.1GROUNDINGGENDEREQUITYASADRIVERWITHINCIRCULARECONOMIES©BenedicteKurzen/NOORforFAO30BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURECurrently,theoverallrateoftimberharvestinganddeforestationinnaturalforestsisfasterthantheoverallregrowthofforests.Relativetomajorend-usessuchasfuelandpaper,theconversionoftimberintowoodbuildingmaterialsoffershugecarbonreductionsbecausethesematerialscanserveaslong-termcarbonstorageoverabuilding’slifetime(Chur-kinaetal.2020;Mishraetal.2022).However,thismodelofbuildingmaterialsasa“carbonsink”assumesthatsustai-nablereplantingoftreesoccurs.Currently,thisisthecaseonlypartiallyinEuropeandNorthAmerica,wheretherisingdemandforwoodproductsiscoupledwithacapacityforafforestationpractices.Intropicalandsubtropicalforests,increasedloggingdrivesdangerouslevelsofdeforestation,ultimatelyreducingthelong-termcapacityofnaturalforeststosequestercarbon(Vogtländer,vanderVeldenandvanderLugt2014;vanderLugtetal.2015).BOX4.2TAKINGPRESSUREOFFWESTAFRICA’STROPICALFORESTSTHROUGHTHEUSEOFNON-TIMBERBIOMASSRESOURCESInSenegal,localtimberproductionsupplies5percentofthecountry’sdemand(Berthome,SilvertreandKouame2013)andreliesprimarilyonwoodharvestedfromtheregionsofTamba-coundaandKolda.However,keytreespeciesintheseareasarethreatened,includinglinké(afzeliaafricana),caïlcédrat(khayasenegalensis)anddimb(cordylapinnata)(Berthome,SilvertreandKouame2013).In2020,Senegalalsoimportedmorethan100,000tonsofwoodfromelsewhereinWestAfrica,primarilyfromCôted’Ivoire,theregion’sleadingtimberproducer.TimberharvestingisalsoincreasinginGhana,whereloggingratesareestimatedtobedoubletotriplethelegalannualallowablecuts,withadverseeffectsonbothforestareaandregionalbiodiversity(Oduro2016).Becauseofoldmillingequipmentandthelackofoperatortraining,timberproductioncompaniesinWestAfricaloseanestimated20-40percentoftimbermaterials.This,inturndriveshigherharvestingratestomakeupfortheloss(Asamoahetal.2020).Toacceleratecircularpracticeson-siteinsuchcontexts,criticalnear-termactionsincludetrainingandupskillingtimbermanufacturingworkersandinvestinginupgradingofmillingequipment.GiventhehistoricalchallengesandrisingdemandinWestAfrica’stimberindustries,thereisanopportunitytoreduceemis-sionsandacceleratethedevelopmentofmarketopportunitiesbysubstitutingtimberandstructuralmaterialswithnon-timber(plant-based)biomassresources,suchasbamboo,coconutandtyphacomposites.Localtimberindustryproductscanbeusedforflooringandwindowanddoorframing,andless-usedtimberspeciescanbeusedformainconstructionactivities(suchasengineeredbambooduetoitsrapidgrowthrate).Agriculturalbiomassfeedstockscangeneratefeweremis-sionsintheirproductionandstorecarbonduringtheirlifetimeinabuilding.However,investmentisneededintheresearchanddevelopmentandcommercialisationofawiderrangeofagriculturalfeedstocksinWestAfrica.Currenteffortsevaluatetheuseofcoconuthuskby-productsfromtheregion’scoconutfoodindustrytomanufacturemediumtohigh-densityfibreboardsasanalternativetolocalreconstitutedwoodproducts(Lokkoetal.2016).Suchstudiesshowtheimpactofcoconutfibreboardhygrothermalbehaviourinreducingoperationalcarbon(LokkoandRempel2018).Intotal,anestimated38percentoftheworld’swoodproductsareusedinthebuiltenvironment,roughly1,800milliontonsin2020(FAO2020).Around10-30percentofthetimbertradedworldwideisharvestedillegally,asharethatmayreach90percentfortropicalhardandsoftwoods(GraceFarmsFoundation2022).Illegalloggingoperationsarevaluedatupto$100billion,oranestimated10-30percentoftheglobaltimbertrade(GraceFarmsFoundation2022).Globally,asmuchashalfofillegalloggingisdependentonforcedlabour.Inadditiontothehazardousnatureofloggingactivities,exploitativeconditionsmayincludethreats,poorlivingandworkingconditions,excessiveworkhours,non-paymentofwagesanddebt-basedcoercion(Vidican2020).Genderinequalitiesarealsorife,withwomenoftenengagedinuncompensatedinformalwork(seeBox4.1).©MindenPictures/AlamyStockPhoto31BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREDESIGNFORDISSASEMBLYTORE-USECOMPONENTPARTS©KengoKumma&Associates+CollegeofEnvironmentalDesignUCBerkeley/ShinkenchikuSha4.3Embodiedcarbonbalanceofcross-laminatedtimberandforestbyproductsProducingcross-laminatedtimberbothstoresandemitscarbon,andtheuseofby-productsfromtheprocessalsooffersopportunitiesforcarbonstorage.Note:Note:Transitioningtobio-basedmaterialsandtimberinvolvesbothafforestationpracticesandcircularity,asmaterialsmadefromforestby-productscanstorecarbonandoffsetemissionsfromdecay.Source:Lanetal.2020.DecayonLandRecyclingForestOperationsConstructionProductionLandﬁllMaterialWastefromDurableWoodBy-productsLandLandﬁllDecayLivingTreesCLTPanels400400280130-230-370-120-300-450-45027020013070STORAGEEMISSIONS0200400600-600-400-200Cross-LaminatedTimber(CLT)ForestBy-product-500-300-400-110-180-300CarbonBalanceGHGEmissions(MtGtCO2eq/hectare)100years25years(loggingevent)25years(loggingevent)100yearsMostCarbonEmissionsfromTimberProductionArefromHarvesting,TransportandManufacturingTimber-basedbuildingmaterialsrelyheavilyontoxic,chemicalgluesandfossilenergy.Carbonemissionsinthetimberindustryareconcentratedinthephasesofharvesting,transportandwoodmanufacturing(Steel,OfficerandAshley2021).PreviousestimatesofCO2emissionsfromtimberharvestingunderestimatedemis-sionsassociatedwithpesticides,fertiliserandherbicideuseaswellas“clear-cuts”(thedecayinglogsandresiduesfromlogging).Together,theseaccountforanestimated15percentofloggingemissions(Lippkeetal.2011;HytönenandMoilanen2014).IntheUnitedStatesofAmerica,evenwhenlong-termcarbonstorageinwoodproductsistakenintoaccount,theCO2emissionsfromtimberloggingandwoodmanufacturingexceedthosefromtheresidentialandcommercialsectorscombined(Talberth2019).Themanufacturingofstructuralbeams,panelsandengineeredwoodproductsreliesheavilyontheuseoftoxic,chemicalgluesandfossilfuelenergy(Bergmanetal.2014).However,emergingtimber-basedmaterialssuchascross-laminatedtimberandforestryby-productsofferthepotentialtobalanceouttheseemissionsoverthebuildinglifecyclethroughcarbonstorage(Lanetal.2020)(seeFigure4.3).Aseffortstomodeltheglobalstorageofcarboninwoodproductsadvance,akeyareaforlong-termCO2emissionreductionisthroughimprovingharvestingpracticesandwoodmanufacturingprocesses(BuchananandLevine1999;Talberth2019).ImportanteffortstoadvanceimprovedharvestingpracticesandtoreducepressuresontropicalforestsareoccurringinWestAfrica(seeBox4.2).32BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREKEYSTEPSTOEXPANDTHESUSTAINABLEUSEOFTIMBERANDWOODINBUILDINGSSupportandenforcesustainablenaturalforestmanagementandafforestationpractices>Policiestargetingtheownersofindustrialforestlandsarekeytoimprovingsustainablemanagementofnaturalforestsandtransitioningtoproductiveplantations(Pirard,DalSeccoandWarman2016).>Policiesandplansshouldencourageafforestationofadiversityofsoftwoodandhardwoodtreespeciesandreductionintheuseofchemicalherbicidesandfertilisers.>Usingbiomassfromclear-cutsasanon-sitefuelsourceisakeynear-termsolutiontoavoidCO2emissionsandfossil-basedelectricityuse(GustavssonandSathre2011;Bergmanetal.2014).>Fortropicalforestproductioncountries,adoptingforestcertificationandtimbertrackingmanagementpracticescouldreduceemissionsfromdeforestationandforestdegradationby29-50percentandimprovecarbonstorageinsawnwoodproductsandreducewoodwasteby14-184percent(Sasakietal.2016).Enhancematerialrecoveryfromforestby-productsandwoodmanufacturing>Clear-cutsandoff-cutsfromwoodmanufacturinghavepotentialtoserveasfeedstocksforuseinpanelling,boards,furnitureandflooringapplications.>Recuperationofforestdetritusandupgradinginfrastructurescouldminimisetreefellingforprimarytimberandsavevastamountsofcarbonbyhelpingtoreduceforestfires(YaleCarbonContainmentLab2022).Transitionwoodmanufacturingtorenewableenergysources>Encouragetheupgradingofexistinginfrastructuretouseofrenewableenergysourcesinwoodmanufacturing.Replacepetrochemical-basedglues,chemicalsandcoatingsinwoodproducts>Replacingpetrochemicalglueswithbio-basedadhesiveswouldreduceembodiedemissionswhileimprovingthemechanicalandhygrothermalperfor-manceofwoodandreconstitutedwoodproducts.Advancesocialacceptanceofwood-basedproductsinbuildings>Improvesocialacceptanceandaddressregulatorybarriersgoverningfiresafetyinbuildings.>Keypolicyincentivesaimedatstimulatingmarketdemandareneededtobroadlypromotetheuseof©BrockCommonsTallwoodHouse/ActonOstryArchitectsInc/Naturallywood.com4.3BambooKEYMESSAGEBambooisafast-growingrenewableresourcethathaswitnessedsignificantadvancesasabuildingmaterialinthelasttwodecades.However,toreducetheCO2footprintofbambooproducts,investmentisneededinthedevelopmentoflow-carbon,bio-basedtreatmentchemicalsaswellasnon-toxicgluesforlaminatedproducts.BambooOffersExcellentPropertiesandCanBeUsedinManyBuildingApplicationsBamboo’shightensileandcompressivestrengthoffersawiderangeofstructuralapplications.Asafast-growinggrass,bamboocanserveasarenewablefeedstockforarangeofbuildingmaterialusesworldwide.Withatensilestrengthclosetosteelandacompressivestrengthtwicethatofconcrete,bambooisusedforstruc-turalcolumnsandbeams,foundation,flooring,roofingandwalls(ChungandYu2002;HegdeandSitharam2015;Lv,DingandLiu2019;YadavandMathur2021).Progressinengineeredbambooshowsmechanicalperformancecomparabletothatofheavytimber(Sun,HeandLi2020).Bamboopolescanbeadoptedforarangeofscaffolding,shearwallandcomplexstructures.Bamboostructuresarekeycandidatesforuseinseismic(earthquake)andfloodzones,towardsexpandingtheuseofbambooinclimatechangeresilienceplanning.BambooGrowsQuicklyandSequestersMoreCarbonThanForestsPerhectare,bamboosequesters1.46timesthecarbonoffirforestsand1.33timestropicalrainfo-rests.Thebambooplanthasarapidgrowthrateandcanreachmaturityinunderfiveyears;assuch,bambooforestscanplayakeyroleincarbonsequestration(LieseandKöhl2015).Currently,bambooforestsoccupyanestimatedareaof36millionhectaresglobally,oraround3.2percentoftheglobalforestarea(Lobovikovetal.2007;Phimmachanh,YingandBeckline2015).Globally,anestimated30percentofbambooisgrowninforestplantations(BeenaandSeethalakshmi2011).Bambooisconsideredtobeafrontrunnerfordrivingaffores-tationpracticestomitigateclimatechange.Globalstudiesoftheannualcarbonsequestrationcapacitiesofbamboorangefrom5to24tonsofcarbonperhectare;onthelowerend,thisis1.46timesthesequestrationcapacityofforestsand1.33timesthatoftropicalrainforests(YenandLee2011;Nath,LalandDas2015;Yuen,FungandZiegler2017).Unlikethecarbonsequestrationlossesassociatedwithtimberlogging,selec-tivebambooharvestingmaybelessecologicallydamagingtoforests,andproductivespeciescanyieldbetween150-296tonsperhectareofforestplantationland(Seethalakshmi,Bamboo©AndreMoura/PexelsJijeeshandBalagopalan2009).Theglobalavailabilityoflandforscalingupbambooplantationsisdecreasing.However,theglobalavailabilityoflandforscalingupbambooplantationsisdecreasing,indirectcompetitionwithotherlanduses,particularlyforhousingandagriculture(Seetha-lakshmi,JijeeshandBalagopalan2009).CurrentTreatmentsUsedinHigh-QualityBambooProductsAreCarbonIntensiveandNeedFurtherDevelopmentCurrentpracticesforchemicallytreatingbamboorivaltheemissionsofproducingsteel.Mostofthecarbonemissionsfrombambooproductsaregeneratedduringtheproductionstage,whichreliesonarangeoftoxictreatmentchemicalstoimprovethematerial’sresistancetomoldandcorrosion.Theuseofsynthetictreat-mentchemicals,gluesandhigh-temperatureairfordryingcanleadtothetriplingofCO2emissionsrelativetotimber-basedproducts(Xu,Xuetal.2022).Perunitofvolume,studiesdemonstratethatlaminatedbambooproductscangeneratecarbonemissionscomparabletothoseofsteel(seeFigure4.4).However,unlikesteelandcement,bambooalsoofferscarbonstoragepotential,atlevelsslightlyhigherthanforsomeotherharvestedwoodproducts.Overall,bamboo’scarbonemissionspotentialisaround63percent,whereasitscarbonsequestrationpotentialisaround37percent(Xu,Xuetal.2022).Duetothehighcarbonemissionsandecologicalimpactsofchemicalsusedinthetreatmentofbamboo,progressisneededtowardsthedevelopmentoflow-carbon,eco-friendlyalternatives.Currentapproachesincludewaterleachingaswellasprocessesthatrelyonbotanicalpreservativesandtheuseofeffluentsfrompapermillingproduction(Kauretal.2016);suchprocessesoccurlargelyinsmall-scale,experi-mentaloperationstoday.Keywaystoreduceemissionsfrombamboomanufacturingincludere-usingbambooproductsattheirend-of-lifeandprovidingon-siterenewableenergy(Vogtländer,vanderVeldenandvanderLugt2014).KEYSTEPSFORSCALINGBAMBOOASASUSTAINABLEBUILDINGMATERIALExpandpolicysupportforlow-carbonalterna-tivesinbamboomanufacturingandtreatment>Incentivisecommercial-scalebambooindustriestousebio-basedalternativechemicalsfortreatment.>Manufacturersmustgraduallyphaseouttheuseoftoxic,fossilfuel-basedchemicalsandglues.>Researchandinvestmentareneededinthedevelop-mentofnon-toxic,bio-basedtreatmentchemicalsandgluesforlaminatedbambooproducts.Developandpromotetheuseofbamboomaterialstandards>Keyengineeredbamboostandardsprovideguidanceonthetestingandstandardisationofengineeredbambooperformanceforstructuraldesign(ISO2004a;ISO2004b;ISO2022a).Promotesustainablebambooforestplantationmanagementpractices>Highlyproductiveandsustainableplantationmanage-mentpracticescanbeaccelerated,with63percentofresourcesprivatelyowned,unliketimberwhere80percentaregovernment-owned(Lobovikovetal.2007).>LargeandgrowingdemandforbambooincountrieslikeChinaprovidesanopportunityforsustainablemanagementoutcomes,muchastheriseindemandfortimberproductshelpeddriveafforestationandcarbonsequestrationpracticesinEuropeandNorthAmerica(Louetal.2010).Transitionbambooproductiontorenewableenergysources>Transitioningtorenewableenergysourcesformanufacturingiscriticalgiventheenergyrequirementsofbamboomanufacturing,particularlyduringthetreatmentandproductionstages.Scalethebambooplantingstock>Bamboocultivationdependsonseedsfromfloweringplants(Seethalakshmi,JijeeshandBalagopalan2009;Singhetal.2013),buttheshortageofplantingstockisakeybarriertoexpandingbamboo’scarbonstoragepotential.>Novelcultivationmethodsincludeoffsetplanting,culmandbranchcutting,andrhizomeplanting.4.4CarbonemissionsandstorageforlaminatedbambooversusotherbuildingmaterialsLaminatedbambooproductsgeneratesimilaremissionsassteelbutoffercarbonstoragepotential.Source:Xuetal.2022.DimensionedlumberEngineeredlumberSteel2.0kgCO2perkgofmaterialkgCO2perkgofmaterial1.51.51.01.00.50.5CementTimberHempcreteLaminatedbamboolumberSTORAGEEMISSIONS354.3`BiomassKEYMESSAGENon-timberlignocellulosicmaterialstreamsgene-ratedfromforestry,agricultureandbiomassresiduestreamsrepresentkeylocalbuildingmaterialsolutions.Globally,modelsoftheannualbiomasssupplyoutweighsprojectedconstructiondemand.Ifscaleduptosubstituteorreducetheuseofpetrochemicalandtimber-basedbuildingmaterials,fast-growinglignocellulosicmaterialscanlowertheprojectedpeakinCO2emissions,shiftingitby50years.However,suchmaterialstodayrepresentasmallmarketshareofbuildingmaterialsandrelyonexpensiveandcomplexprocessingtechniques.Both“push”and“pull”marketapproachesareneededtoscaleupandensurewidespreadadoptionofbio-basedbuildingmaterials.Policiesthatfinanciallyincentivisethecaptureandvalueadditionofbiomassbuildingmaterialsneedtobecoupledwithmarketingandeducationprogrammes.SuppliesofBiomassResiduesOutweighCurrentandProjectedConstructionDemandBuildingmaterialsfromforestry,agricultureandbiomassresiduesarekeylocalsolutions.Non-timberlignocellulosicmaterialsgeneratedfromforestry,agricultureandbiomassresiduestreamsrepresentkeylocalbuildingmaterialsolutions.Currentmodelsofbambooandstraw,twofast-growingrenewablebiomassresources,showthatannualsupplyoutweighsdemand(Gösweinetal.2022).Eachyear,anestimated140gigatonsofby-productbiomassisgeneratedworldwide(Tripathietal.2019).Currentend-of-lifepathwaysforbiomass,suchaslandfillsandincinerationforenergyrecovery,missoutonthetrueopportunityforvalueadditionandcarbonstorageinlong-lifebuildingmaterials(Langholtz,StokesandEaton2016;Lan,ZhangandYao2022).Biomass-BasedConstructionCanResultinLowerCarbonEmissionsWhilecross-laminatedtimberassembliesareadvocatedasthekeyload-bearingalternativestoconcreteandsteel,suchapproachesoverlooktheinabilityofthecurrenttimbersupplytomeetprojecteddemand.Ingeneral,whencomparedwithtraditionalwoodframeconstruction,wallsystemsmadefromcross-laminatedtimber,bambooandcoconut-biomassagriculturalresiduesdemonstratemuchlowerCO2emissionsandenvironmentalimpactsonalife-cyclebasis(Keenaetal.2022)(seeFigure4.5).Acrossthesebio-basedmaterialassemblies,design-for-disassemblystrategies,which©EcoCoconBiomass4.5Comparisonoflife-cyclecarbondioxideemissionspersquaremetreforfourwallassemblytypesWallsystemsmadefromcross-laminatedtimber,bambooandcoconut-biomassresiduesshowemissionsavings.AdaptedfromKeenaetal.2022.kg(CO2eq)TraditionalEngineeredWoodFramingCross-LaminatedTimber(CLT)EngineeredBambooBiomassAgriculturalResidueEnd-of-LifeTreatmentBio-basedMaterialsInorganicMaterialssingle-usesingle-usesingle-usesingle-usedesign-for-disassemblydesign-for-disassemblydesign-for-disassemblydesign-for-disassembly05101520253040455035singleuseDfDsingleuseDfDsingleuseDfDsingleuseDfDenablecomponentre-use,havebeenshowntoresultin10-50percentCO2emissionreductions(Keenaetal.2022).Ifscaleduptosubstituteorreducetheuseofpetrochemicalandtimber-basedbuildingmaterials,fast-growingligno-cellulosicbiomasscanlowertheprojectedglobalpeakinCO2emissions,shiftingitby50years(ibid.).However,coor-dinationmustbeimprovedalongthesupplychaintoavoidincreasedemissionsfrombiomasscollection,treatmentandmechanicalprocessing.Biomassfeedstockscanbeofpoorornon-standardisedquality,andtheiravailabilitycanbehighlydistributedorerratic.Livingbiomasssystemscanreduceoperationalcarbonemissionsinbuildings.Inadditiontobiomass-basedmaterials,theintegrationoflivingbiomasssystems—suchasgreenroofs,façadesandindoorwallassemblies—inbuildingscanbringdecarboni-sationbenefitsbyreducingheatingandcoolingloads,whilealsohavingthepotentialtoimproveairquality(seeBox4.3).StrawbaleInsulationHasProvenCarbonBenefitsStrawbiomassoffersalow-carbonopportunitytoreplacepetrochemical-basedinsulation.Strawbiomassoffersacriticalopportunitytoreplacehigh-carbonpetrochemical-basedinsulation.Strawisthewidelyavailableleftoverstalkharvestedfromadiverserangeoffast-growingcerealplants,suchaswheat,maize,riceandothergrains.Comparedwithconventionalinsulationmate-rials–includingpolystyrene,mineralwood,cellulosefibresandrockwool–strawbaleinsulationdemonstratesmuchlowerCO2emissions(KohandKraniotis2020),withthemarketopportunityforbio-basedinsulationgrowing.Whenintegratedintowalls,strawhasdemonstratedtheabilitytoreduceoperationalcarbon.Load-bearingstrawbalehouseshavebeenfoundtohaveacarbonfootprintofbetween20and1,000kilogramsofCO2persquaremetre,comparedtomorethan600kilogramsofCO2persquaremetreforconventionalconstruction(Bocco2014;BoccoGuarneri2020;KohandKraniotis2020).Thiswidecarbonfootprintrangehighlightstheimportanceofdesignforeffectiveintegration.CarbonBenefitsofMyco-BasedBiomassStillNeedtoBeDemonstratedatScaleMyco-basedmaterialsharnessfungi’scapacitytotransformbiomassintobuildingproducts.Anotherpromisingbio-basedoptionthathasemergedoverthelasttwodecadesistheuseofmycelium,thevegetativestateoffungi.Myco-basedbuildingmaterialsaregainingattentionduetofungi’scapacitytobindawiderangeofcellulosiccomponentsofagricultural,forestryandfoodbiomasswastestreamsintochitin-boundbuildinginsulation,fibreboard,particleboardandbio-brickproducts.However,moreresearchisneededonthescalabilityofmethodsandthecarbonfootprintofthesematerials.Duetotherequirementsforhigh-qualitybiomass,myco-pro-ductionentailshighlevelsofrefrigerationanddrying,requi-ringtheuseofplasticmouldsandsterilisation.Myceliumenterprisesareoftenunabletoobtainsufficientsuppliesofhigh-quality,consistent,single-streambiomassandmayturntoimportinghighqualityfeedstocks,furtherdrivingupemissions.Overall,advancementshavebeenmadeindevelopingmate-rialrequirementsaswellasproductionandconstructionstandardsforbiomass-basedbuildingmaterials.However,toacceleratetheiruptakeinbothretrofitsandnewconstruction,financialincentivesareneededtopromotedevelopmentofmethodsalongsidecircular,biodiversedesignapproaches.37BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE4.6Examplesofgreenbuildingenvelopesusinglivingbiomassandotherclimate-friendlyfeaturesLivingsystemshaveshownpromiseinreducingheatingandcoolingloadsandtheurbanheatislandeffect.Source:ARUP2016.4.7RelationshipbetweenembodiedandoperationalcarbonwithinlivingbiomassmaterialsystemsTrade-offsexistbetweentheembodiedcostsofassemblingthesystemsandtheirabilitytooffsetorstore.Source:CiardulloandDyson2022.ASSEMBLYMATERIALTrade-offsexistbetweentheembodiedcostsofassemblingthesystemsandtheirabilitytooffsetorstorecarbon.AdditionalStructuretoCarryWeightofSoilandWaterMaterialsandSystemstoSupportPlantGrowthCostsofRepairandMaintenanceCostsofWaterandFertilizerUseofCarbonStoringMaterialsExtendedLifeofSubstructureUseofRecycledorBy-productMaterialsReductioninHeatingandCoolingLoadsReductioninEnergyofVentilationMATERIALANDASSEMBLY-SCALEIMPACTSBUILDING-SCALEIMPACTSURBAN-SCALEIMPACTSEnergyUsefromWaterandLightingEmissionsfromLandﬁllEMBODIEDCarbonOffsetsfromUrbanAgricutlureOngoingCarbonStoragefromLivingSystemsReductioninUrbanHeatIslandReductioninStormwaterInfrastructurecostbeneﬁtOPERATIONALcostbeneﬁtPRODUCTION/CONSTRUCTIONEND-OF-LIFEUSE38BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE39KEYSTEPSFORSCALINGBIOMASSASASUSTAINABLEBUILDINGMATERIALImprovemanagementofthebiomasssupplychain>Provideopportunitiesforsmallandmediumbio-basedenterprisesandstart-upsinordertocompetewithwell-establishedreconstitutedwoodandpetroche-micalinsulationindustries(Langholtz,StokesandEaton2016).>Integrateapproachestolanduse,residuemanagement,andthecreationofeco-manufacturingfirmsinordertolowerthecostsofbiomasscollection,increaseavailability,andimprovequalitycontrolandproductstandardisationEncouragebiomassuseinbuildings,ratherthanforshort-livedenergyandindustrialapplications>Incentiviseindustrytousebiomassforlonger-lifeapplications,asshort-livedapplications,suchasfuelorpaperproducts,drivesupemissions.Createincentivestoencouragetheconversionofbiomassintobuildingmaterials>Policysupportisneededtoencouragetheconversionofbiomassfeedstocktomaterialssuchasbio-basedinsulation,bio-aggregateproducts,andalternativestotimberandwoodproducts.>Both“push”and“pull”marketapproachesarerequiredtoscaleupadoption.>Policiesthatfinanciallyincentiviseintersectoralcollaborationneedtobecoupledwithconsumercampaignsandtechnicaltrainingforarchitecture,engineeringandconstructionstakeholders.Reducethepotentiallyhighembodiedcarbonassociatedwithbiomass-basedmaterials>Coordinationandresearchmustbeimprovedalongthesupplychaintoavoidincreasedcarbonemissionsfrombiomasscollection,treatmentandmechanicalprocessing.Promotejustlabourpracticesinbiomassindustries>Acriticalleverforbiomassindustriesintheneartermistoensurequalitativegainsacrossthewholelifecycle,includingensuringhealthyandjustlabourconditionsandenvironments(Heerwagen2000;Loftnessetal.2007).BOX4.3THEBENEFITSOFINTEGRATINGLIVINGBIOMASSSYSTEMSINBUILDINGSManymunicipalitiesgloballyhaverecognisedthebenefitsofintegratingvegetatedsurfacesorlivingmaterials(plan-tings,soils,andstructuresthatsupportthem)asasolutiontoreduceurbancarbonemissions(Liberalessoetal.2020).Suchlivingbiomassmaterialsystems–includinggreenroofs,façadesandindoorwallassemblies(seeFigure4.6)–canofferecosystemservicesthathavebeendisplacedbyurbanhardscaping(Mansoetal.2021;Shafiqueetal.2018)Comparedwithconventionalmaterials,livingbiomassmate-rialsystemsprovidecomparableorimprovedenergysavingsfrominsulatingandcoolingeffects(Shafiqueetal.2020;Bevilacqua2021;Theodosiou2009)).Somelivingwallsystemscontributeupto58.9percentenergysavingscomparedwithexposedconcretewallsystems,particularlyinhigh-sunareas(Comaetal.2017).Inaddition,suchsystemshaveconsistentlybeenshowntoreducetheurbanheatislandeffect(Santamouris2014;Shishegar2014)andtooffsetthecarboncostsofurbanstormwaterinfrastructure(Berndtsson2010;Wang,EckelmanandZimmerman2013).Inindoorapplications,livingsystemscanimproveairqualityandreducetheenergycostsofmechanicalventilation(FengandHewage2014;Torpy,ZavattaroandIrga2017;Mankiewiczetal.2022).Theabilityforexteriorsystemstoactivelyparticipateinongoingcarbonsequestrationisstillunderinvestigation(Whittinghilletal.2014).OnestudyconcludedthatconvertingallexposedconcretebuildingroofareasintheU.S.cityofDetroittolow-profilegreenroofswouldhavethesamecarbonsavingsasremoving10,000sportutilityvehiclesfromtheroad(Getteretal.2009).Eachlivingbiomasssystemishighlydependentondesign-specificelements,includingthetypeofstructureused,thechoiceofplantspeciesandgrowingmedia(seeFigure4.7).Designchoicesrevealanintegratedrelationshipbetweenembodiedandoperationalcarbon(Ciardulloetal.2022;Mankiewiczetal.2022,KosareoandRies2007,KoroxenidisandTheodosiou2021;Roweetal.2022;Susca2019).Forexample,systemsthatrequireadditionalmaterialsforirrigationsystemsorforsub-structuresthatcarrytheweightofsoilandwatercanhavehigherembodiedcarbon(Otteleetal.2011).However,thisrelativelysmallincreaseinmaterialmightbeoffsetbyoperationalcarbonsavings,asadditionalsoilthicknessandwater-holdingcapacityhasmoreimpactonreducingheatingandcoolingloads(Raji,TenpierikandvandenDobbelsteen2015,Rowe2011).Theembodiedcostsofbiomasssystemsmightbeoffsetinthefuturethroughtheuseofrecycled,renewableandlightweightmaterialsubstrates(Rinconetal.2014;Chenani,LehvävirtaandHäkkinen2015;Tams,NehlsandCalheiros2022),organicfertilisers(Chaferetal.2021)andsystemdesignsthatreducewateruse(Natarajanetal.2015).Becausemanybenefitsoflivingbiomassmaterialsystemsmanifestattheurbanscale,municipa-litiesshouldexpandincentivesforthesesystemstohelpoffsetinitialandongoingmaintenancecosts.395Duetotheongoingglobalconstructionboomindevelopingeconomies,itisimperativetoprioritisethedecarbonisationofconventionalmaterialproductionandmandatethedesignofcircularcomponentsforconcrete,steel,aluminium,glassandplastics.IMPROVEConventionalBuildingMaterialsandProcesses405.1DecarbonizingConventionalBuildingMaterialsInthenearterm,non-renewablematerialswillcontinuetocomprisethemajorityofbuildingmaterials.Withintheconstructionsector,cementandconcrete,aswellasironandsteel,playadominantrole(seeFigure5.1).Inadditiontotheiremissionimpacts,manyofthemostcommonbuildingmaterialsarenot-renewable,meaningthatrawmaterialsuppliesarefiniteandcannotbereplenished.Conventionalnon-renewablematerials–cement/concrete,steel,aluminium,petroleum-basedplasticsandglass–willcontinuetocomprisethemajorityofbuildingmaterialsfordecadestocome,andcannotalwaysbereplacedwithrenewablealternatives.Giventheirubiquityandrisingdemand,itiscriticaltodecarbonisethemajorconventionalbuildingmaterialsandprocess,pursuingparallelbutverydifferentpathways.Addi-tionally,promisingavenuesexisttoscaleuptheuseof“tran-sitional”buildingmaterials,specificallyearth-basedmasonryproducts,whicharenon-renewablebuttypicallyhaveloweremissions.Theseincludeadobeblocks,compressedearthblocks,firedbricks,andTyphaclaycomposites,whichcanserveaspotentialsubstitutesforhigh-carboncement-basedblocksifcertificationsandstandardsaredevelopedandenforced.Inadditiontotheiremissionimpacts,manyofthesupplychainsforconventionalbuildingmaterialsareathighriskforunethicalworkingconditions.Thematerialswiththehighestriskofbeingmadewithforcedlabourarerubber,glass,fibreandtextiles,steel,electronics,bricks,timber,stone,copper,ironandminerals.Asconventionalmaterialsareincreasinglydecarbonised,itisessentialthatfairlabourconsiderationsarecoupledwithenvironmentalpolicytargets.(Tosupportdecision-makingonthesecombinedsocio-economicimpacts,seetheDesignforFreedomToolkit,GraceFarmsFoundation2022.)Keytoalleffortswillbeelectrifyinganddecarbonizingtheenergythatisusedtoproduceandmaintainbuildingsandmaterialsacrosstheirlifecycle.Inaddition,regionscanavoidtheextractionofresourcesbyshiftingfromunsustainableminingofmaterialstowardsintegrationofrenewablecomponentsandmethods.Reducingrawmaterialextractionandharvestingcanalsomitigatemanysocialillssuchasforcedlabourissuesupstreaminthesupplychain.Toadvancethecircularityofconventionalbuildingmaterials,thesupplyofrecycledcontentwillneedtocatchupwiththegrowingdemandformaterials.5.1Sharesoftotalgreenhousegasemissionsbysource,materialclassandindustrialsectorCementdominatestheemissionsimpactofconstruction,followedbysteel.Source:Hertwich2021.Source(%)TotalEmissions(GtCO2eyr-1)5010019952005202500612otherminingenergysupplymaterialproductionMaterial(%)TotalEmissions(GtCO2eyr-1)0612501001995200520250plasticandrubberwoodproductsothermineralsglasscementothermetalsaluminiumironandsteelUse(%)TotalEmissions(GtCO2eyr-1)1206501001995200520250ﬁnaluseservicesotherproductselectronicstransportequipmentmetalproductsmachineryconstruction5.1©NatalieFobes/GettyImages41BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE5.2ConcreteandCementKEYMESSAGETheconcreteandcementsectorhasadisproportionateimpactongreenhousegasemissionsandwillcontinuetodosoformanydecades.Evenifalloftheexistingmethodstoreducetheclimateimpactsofthesectorweresuccessfullyimplementedandscaled,additionalfundingwouldstillbeurgentlyrequiredforpublic-privatepartnershipstoacceleratethedevelopment,demonstrationandcommercialisationofdecarbonisationstrategies.Keystrategiesinclude:1)chemicalcarbonreductionofconcreteandcementproductiontechniques;2)carboncaptureandstorageatmanufacturingplants;3)designfordisassemblyandre-useofcomponents;4)novel(bio-based)concretemixturestoreducebinderrequirements;and5)computer-assistedandadditivemanufacturingtoreducecarbonemissionsfromtransportandon-siteconstructionwaste.ConcreteIsWidelyUsedinBuildingsandConstructionButIsNotAlwaysNeededManyconcretebuildingsoflessthan12storeyscouldshifttobio-basedstructuralassemblies.Concreteisbyfarthemostwidelyusedconstructionmate-rialintheworld,dueinparttoitsstrengthanddurability.Itisproducedbymixingcementandwaterwithanaggregate,typicallysandorgravel.In2020,4,300milliontonsofcementwereproducedglobally(IEA2022a).Concretemixturesareusedforbothresidentialandnon-residentialbuildingsandforinfrastructure(e.g.,railways,bridges).Concretehasexperienced10-foldgrowthoverthepast65years,comparedwitha3-foldincreaseinsteelproductionandnear-stagnantgrowthintimberproduction(Monteiro,MillerandHorvath2017).Globally,in-usecementstocks–theamountofcementembeddedinexistingbuildingsandinfrastructure–havesurgedinAsia,whiletheyareflatteninginEuropeandNorthAmerica(seeFigure5.2).Sincethemid-2000s,Chinahasbuilttheworld’slargestin-usecementstocks,mostlyinitsbuildings(80percent)andtoalesserextentinitsinfrastructure(20percent)(Caoetal.2017).©RicardoGomezAngel/Unsplash42ConcreteandCementInmanyapplications,includinghousing,concreteisusedwherelower-carbonmaterialscouldsuffice,largelybecauseconcretehasadevelopedsupplychainandinfrastructure,witheaseofuseandcalculation.Manyconcretebuildingsoflessthan12storeyscouldshifttobio-basedstructuralassembliesforeverythingbutthefoundationandelevatorshafts,ifsustainablematerialswereavailable.ConcreteContributestoRisingGlobalGreen-houseGasEmissions,AmongOtherImpactsCementproductionaccountsfor7%ofglobalCO2emissions.Incementmanufacture,rawmaterialsaremilledtoahomogeneouspowderbeforebeingheatedathightempe-raturesintoclinker.Theclinkerisblendedwithgypsumtoproducecement(IEA2018a).Cementisthebindingmaterialinconcrete,typicallycomprisingaround10-15percentofthetotal(Habertetal.2020).However,cementitiousmaterialsarebyfarthemostcarbon-intensivetoproduce,withcementproductionaccountingforaround7percentofglobalCO2emissions(Hasanbeigi2021).Cementproductionisconsideredtobeoneofthemostdiffi-5.2Totalin-usecementstocks,byregion,1931-2014In-usecementstockshavesurgedinAsiabutareflatteninginEuropeandNorthAmerica.Source:Caoetal.2017.5.3DominanceofconcreteandcementintheembodiedemissionsofnewlyconstructedbuildingsWithinconcreteproduction,themainemissionsarefromcementproduction,inparticularlimestoneprocessing.Note:Figure(a)comparestheoperational(heating/ventilation/coolingoverlifetime)andembodied(constructionandmaintenance)greenhousegasemissionsfromtheexistingglobalbuildingstockversusnewconstruction.Figure(b)showsthatfornewconstruction,thelargestemissionsfromatypicalmulti-familyconcretebuildingcomefromconcreteproduction.Figure(c)showsthatwithinconcreteproduction,themainemissionsarefromcementproduction,inparticularlimestoneprocessing(d).Source:Habertetal.2020.EuropeFormerSovietUnionAfricaMiddleEastIndiaLatinAmerica&CaribbeanNorthAmericaOtherAsiaOceaniaChina2014EuropeFormerSovietUnionAfricaMiddleEastIndiaLatinAmerica&CaribbeanNorthAmericaOtherAsiaOceaniaChinaTotalin-usecementstock[Mt]500019311941195119611971198119912001201110,00015,00020,00025,0005.1.1ExistingBuildingsTheBuildingStock(a)(b)(c)(d)OneBuildingOneCubicMeterConcreteOneCementBagNewConstructionOtherSanitaryequipmentElectricalequipmentFinishingInsulationWindowsBricksSteelreinforcementConcreteOn-siteplacementTransporttoconstructionsiteConcretemixingTransportrawmaterialSupplementaryCementingMaterialprocessingCementproductionGravelproductionSandproductionAdmixtureproductionConcretePlacementConcretePlacement002040608010050100CementGrindingSupplementaryCementingMaterialproductionLimestonedecarbonizationConcreteProductionCementﬁnalproductionFuelburnedFuelProductionandtransportMaterialproductionRawmaterialtransportandpreparationOperations:HeatingoverLifetimeEmbodied:ConstructionandMaintenanceGHGemissions(kgCO2e/m2)RelativecontributiontoCO2emissions(%0)EMBODIEDOPERATIONALConcreteLimestoneDecarbonizationCementProduction43BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREcultindustrialprocessestodecarbonise(Davisetal.2018).Thisisbecausethemajorityofthecarbonemissions(55-70percent)arereleasedinthechemicalprocessofconver-tinglimestonetocalciumoxide;another30-45percentofemissionsstemfromfuelcombustionduringtheproductionprocess(IEA2018a;Caoetal.2020).Overall,producingonetonofclinkerinamoderncementplantcangeneratearound600kilogramsofCO2(Fennell,DavisandMohammed2021).Electrificationofcementproductionwithrenewablesourcescansubstantiallyloweremissions.Fornewconstruction,thelargestembodiedemissionsfromatypicalmulti-familyconcretebuildingarefromcementproduction,inparticulartheprocessingoflimestoneintoclinker(seeFigure5.3).Thispointstotheurgentneedtoreinventthecementitiousbindersusedinconcretemixtures.Traditionally,ordinaryPortlandcementhasbeenusedasthebindertoproduceconcreteandmortar;however,itisthematerialresponsibleforthehighestCO2emissionsincementproduction.Toaddressrisingemissionsfromthesector,thesubstitu-tionofconventionalcementcomponentswithlow-carbonalternativesiskey,suchasby-productsfromindustrial,agri-cultural,forestryandend-of-usesources.Inthenearterm,cementdemandcanbereducedusingavailablemeansbyefficientlyoptimisingtheratioofcementinconcretemixesandreducingrampantwasteinconstructionduetolackofoversightandcertification.5.4Evolutionarystagesofpercapitain-usecementstocks,bycountryFuturegrowthincementusewilllikelybehighestinAfricaandSouthAmerica,followedbyAsia.Note:Thecolouringofcountriesfollowstheprogressivestagesofpercapitacementuseshowninthechartatbottomleft.Source:Caoetal.2017.5.5Potentialforregionstoleapfrogtowardsmorewealthandlesscarbon-intensivecementThroughmaterialefficiencystrategiesandlow-carbonproduction,countriescandecouplecementusefromincome.Source:AdaptedfromSchmidt2017.EvolutionaryModeProgressiveStagesPercapitaIn-useCementStockTypeANodataTypeBTypeCTypeDTypeEPercapitacementconsumptionPercapitagrossdomesticincomeGlobalPathPossibleAfricanPathAfricaEurope5.1.344BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREConcretehasothernegativeenvironmentalimpactsacrossitslifecycle.Inurbanareas,concrete,alongwithasphaltsurfaces,absorbmoreheatthannaturalvegetation,dispro-portionatelycontributingtourbanheatislandeffects(Moha-jerani,BakaricandJeffrey-Bailey2017)andtotherisingglobaldemandforcarbon-intensivecoolingandair-conditioningsystems.Theimpervioussurfacescreatedbyconcreteandasphaltcontributetosurfacerun-off,pollutingwaterwaysandcausingsoilerosionandflooding.DevelopingCountriesHaveanOpportunitytoLeapfrogGlobalTrendsinConcreteUseSincetheearly2000s,ChinaandotherAsiancountrieshavedominatedglobalcementdemand,accountingfor80percentofcementproductionin2014(Rissmanetal.2020).Theregion’shighuseofcementhassurgedtomeettheinfrastructureneedsofanexpandingmiddleclass.Thisrapidgrowthisinlinewithastudyacross184countriesthatlinkspercapitain-usecementstockstolevelsofaffluence(Caoetal.2017).Thestudyfoundthatascountriesdevelopeconomically,theygothroughfiveprogressivestages:fromlittlecementusepercapita(A),toatake-offstagewithhighgrowthrates(BandC),followedbyaslow-downstage(D)andeventuallyashrinkingstage(E)(seeFigure5.4).ThefigureshowsthatAfricaandSouthAmericahavethelowestpercapitain-usecementstocks(green)followedbymostofAsia(blue).Chinaisinaphaseofrapidgrowth(red),whereasEurope,NorthAmericaandOceanianolongerhavestronggrowthincementstocks(yellow).JapanandSweden,meanwhile,areseeingadecline(brown),whichisattributedinparttosuccessfulmaterialefficiencystrategiesthatallowforthesamebuildingandinfrastructureservicesbutwithlesscementuse.ThesehistoricalpatternssuggestthatChina’srapidgrowthincementusecouldreachsaturationinthenearfuture,andthatfuturegrowthwillbehighestinAfricaandSouthAmerica,followedbytherestofAsia.However,itwillbecrucialtobreaktheglobalpatternofrisingcementusewhilesimultaneouslyincreasingthelivingstandardsandurbanisationratesoflow-incomecountries.Ideally,thesecountrieswillimplementamixofmaterialefficiencystrategies,coupledwithlow-carboncementproduction,thatenablesthemtoleap-frogtowardshigheraffluencewithrelativelylowpercapitacementconsumption(seeFigure5.5)(Schmidt2017).Akeyenablingtoolwillbereductionoftheclinker-to-cementratiobyusingnovelsupplementarycementitiousmaterialsfromforestryandagriculturalby-products.Evenwithashifttowardsbio-basedmaterials,therapidgrowthinurbandensityandinfrastructureindevelopingcountriesmeansthatthehigh-carboncementandconcretesectorwillcontinuetosoarfortheforeseeablefuture.Alternative,Low-CarbonCementBindersCanReplacePortlandCementandReduceEmissions5.6Thewhole-systemspathwayresultsinemissionreductionthroughmoreefficientuseofcementandconcreteNote:ThefigureillustratesthepossibilitytoexpandtheleversfordecarbonisationintheUnitedStatesofAmerica,China,andIndiathroughwholelife-cyclestakeholderaccountability.EachgreybarinthecircularbarchartscorrespondstothesumofcumulativenetCO2savingsacrossthecementandconcretecycleby2060inthebuildingsandroadsectorsforthethreecountries.Source:Caoetal.2021.CementmanufacturingAggregateproductionConcretemanufacturingConstructionUseEnd-of-lifeA:<0.1GtB:0.1-1GtC:1-1.5GtD:1.5-2GtE:2-3GtF:>3Gt5.1.7BACDEFPRODUCTION-CENTRICWHOLE-SYSTEMSDemolitionWasteSpreadingComponentRe-useDowncyclingMore-IntensiveUseLifetimeExtensionFabricationYieldImprovementMaterialSubstitutionMaterial-EfficientDesignKilnThermalEfficiencyElectricalEfficiencyLow-CarbonFuelLower-CarbonCementChemistriesClinker-To-CementRatioReductionsCo2MineralizationCo2CuringAt-PlantCarbonCaptureandStorageKilnThermalEfficiencyElectricalEfficiencyLow-CarbonFuelLower-CarbonCementChemistriesClinker-To-CementRatioReductionsCo2MineralizationCo2CuringAt-PlantCarbonCaptureandStorageABCDEFWASTEMANAGERDEMOLISHERPROPERTYOWNERURBANPLANNERGOVERNMENTCONSTRUCTIONENGINEERARCHITECTCEMENTPRODUCERWASTEMANAGERR&DENGINEERMATERIALSSCIENTISTAGGREGATEPRODUCERCONCRETEPRODUCER45BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREWithmanyregionallyavailableoptions,mostmajorcement-producingcountriescouldsubstitutealternativelow-carbonoptions.Significantpotentialtodecarbonisecementitiousmaterialsexistsalongtheirlifecycle,withthelargestopportunitiesoccurringintheproductionstage(57percent),followedbymanufacturing(23percent)andend-of-use(14percent)(PamenterandMyers2021).Duringproduction,theuseofalternative,low-carbonmaterialsforconcretebinderspresentsthelargestdecarbonisationpotential(seeAnnex2).Unlikeforflyashandgranulatedblastfurnaceslag,thereisnosupplyshortageformanyalternativesecondarycementitiousmaterials,especiallybio-basedonesderivedfromagriculturalby-products.Theroadtonetzeroconcreteby2060willrequirereplacingPortlandcementwiththemanyregionallyavailableoptionsbeingexploredaroundtheglobefromagricultural,forestryandindustrialby-products,aswellasfromend-of-lifemate-rials(seeAnnex2).Mostmajorcement-producingcountriescouldgenerateenoughofthesealternativematerialstosubstitutemostoftheirdemandforPortlandcement,withtheprimaryoutlierbeingChina,theworld’slargestproducerofPortlandcement(Shahetal.2022).Thestudyestimatesthatthetheoreticallyachievablelowestclinker-to-cementratioisaround0.14globally,reflectinga61percentreduc-tionintheuseofPortlandcementcomparedtothecurrentaverage(0.75).WholeLife-CycleThinkingWillEnableMoreEfficientMethodsandUseofCementandConcreteEngagingstakeholdersacrossthevaluechainoffersflexibilityonthepathtonetzero.Withafocusonthethreelargestcementproducersandconsumersglobally–theUnitedStatesofAmerica,ChinaandIndia–Figure5.6describestwodistinctpathwaystoachievenetzeroemissionsinthecementandconcretesectorby2060.Theseare:aproduction-centricpathwaythatreliesentirelyontheeffortsofcementandconcreteproducerstomitigateemissionsfromthesector,andawhole-systemspathwaythatengagesabroadrangeofactors–fromprodu-cerstodesignersandrecyclers–toimplementmoreefficientmethodsanduseofcementandconcrete(Caoetal.2021).Thewhole-systemspathwayresultsinanoverallreductionofdemand(andthereforeemissions)throughamoreeffi-cientuseofcementandconcreteinthebuiltenvironment.Asaresult,itislessdependentontheneedformaximummeasuresattheproductionlevel.Inotherwords,engagingwithallstakeholdersacrossthevaluechainoffersmuch-neededflexibilityonthepathwaytowardsnetzeroemis-sionsby2060.ThisincludesagrowingimportanceoftheBOX5.2EMERGINGRESEARCHONSTORINGCARBONDIOXIDEINCONCRETECapturingcarboninconcreteproductionisanactiveareaofresearcharoundtheworld.However,theexactamountsofCO2thatcouldbeabsorbedbyconcreteareuncertain.ThisapproachshouldbeconsideredemergingandisnotyetincludedinemissioninventoriesoverseenbytheUnitedNationsFrameworkConventiononClimateChange.AttheUniversityofCaliforniaatLosAngeles,aresearchprojectisunderwaytoupcyclecarbonbytakingCO2directlyfromtheexhauststreamofacoalplantandtransformingitintoconcretebuildingblocks.InCanada,thecompanyCarbonCureclaimstohavedelivered2milliontruckloadsofconcreteinjectedwithCO2,saving132,000tonsofCO2(Fennelletal.2022).end-of-usestage,asthemassivequantitiesofstructuresdatingfromthemid-20thcenturyaredueforreplacement.Engagementofstakeholdersacrossthelifecycleiskeytointegratebothproduction-centricandwhole-systemsdecarbonisationscenarios(Caoetal.2021).Forwhole-sys-temsapproachestobeadopted,mechanismsforknowledgesharingandtransferneedtobeestablishedamongprodu-cers,architects,developersandbuildingmaintenanceoperators.However,evenifalltheexistingleversareincen-tivised,immediateactionsareneededtogalvaniseresearchanddevelopmentofinnovativemethods.Merelycapitalisingoncurrentopportunitieswillnotbeenoughtoachievenetzeroemissionsby2060.Moreradicalbutstillspeculativemethodsforcarboncaptureduringproductionshowpromisebutrequirefurtheranalysisanddevelopment.Carboncaptureandutilisationforconcreteproduction(CCUconcrete)hasbeenprojectedtosavebetween0.1to1.4gigatonsofCO2bymid-century,andthereareclaimstoextremelysignificantenhancedstruc-turalperformance(ICEF2016).However,thereareconflictingopinionsastowhetherthebenefitsinincreasedstrengthandoptimisationofmaterialswilloutweighthecarboncostsofcapturing,transportingandincorporatingthecapturedCO2intoconcreteproducts.Toscalethesetechnologies,itwillbecriticaltoverifytheenhancedcompressivestrengthfromCO2curingandmixing,whileensuringthatallelectricityusedinCO2curingissuppliedthroughrenewablestoproduceanetCO2benefitfromCCUconcrete(Ravikumaretal.2021).46BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREKEYSTEPSTOWARDSDECARBONIZINGCEMENTANDCONCRETEShifttorenewableelectricityincementproduction>Thehighestpriorityforcementdecarbonisationistoelectrifythegridandthemeansofproduction,usingrenewableenergyresourcessuchassolarandwindpower.>Electrickilnsshouldbethestandardforanynewlybuiltcementplants(GlobalCementandConcreteAssocia-tion[GCCA]2020;IEA2022b).Prioritiselocallysourcedalternativebinderstoreducetheclinker-to-cementratio>Portlandcementcontainsmorethan90percentclinker(aclinker-to-cementratioabove0.9).>Blendingcanreducetheclinker-to-cementratiotoaround0.75.Inanetzeroscenario,thiscouldgodownto0.69by2025and0.56by2050(PamenterandMyers2021;GCCA2022;IEA2022b).>Reducingtheclinker-to-cementratioto0.5andbelowcouldbeachievedusing(bio-based)secondarycementitiousmaterials.Localprotocolswouldbeneededfortestingandcertification.>Useofcalcinedclaylimestone(LC3)couldreducetheclinker-to-cementratioto0.5usingexistingtechnolo-gies,andisclosetocommercialisation(Scriveneretal.2018;Fennelletal.2022).>Includinglimeclastsincementmixturescouldprovidedurabilityandextendthelifeofconcreteapplications,resultinginenergysavings(Seymouretal.2023).However,buildingcodesanddesignpracticeswillneedtoadapttothevariablematerialproperties(Scrivener,JohnandGartner2018).Avoidunneededconcreteusethroughtraining,buildingstandardsanddesign>Materialscientistsneedtobeeducatedontheplethoraofnewcementproductiontechnologiessotheycanoptimisethematerialinputandtechnologyforthegivencontext;thisrequiresbettercommunicationamongscientists,structuralengineersandarchitects(Schmidt,AlexanderandJohn2018).>Regularlyupdatingbuildingcodestoaccountforthesetechnologicaladvanceswillbekey,ideallycoupledwithincentivesformanufacturerstoproducethemostlow-carboncementandconcrete.>Materialefficiencyshouldbeakeyconsiderationinbuildingdesign,avoidingoverspecificationandusingconcreteonlyinthoseapplicationsthatrequireitsoutstandingstructuralproperties.>Changestobuildingcodes,alongsideeducationofarchitectsandengineerstousebestavailabletechnologies,couldsaveover25percentofcementbyreducingoverengineering(IEA2019).Usedigitalmethodstoimprovematerialefficiencyandallowforpre-fabrication>“Designforcircularity”andsystemsintegrationcanrevolutionisematerialflowsthroughtheuseofdigitalmethodsandartificialintelligence.Industrymustbesupportedtoadaptandmodernise.>Digitalisationacrossthecementlifecycle(viaimprovedprocesscontrols,next-generationmeasurementdevices)canimproveefficienciesandreduceemissions(Fennell,DavisandMohammed2021).>Movinginefficientandemission-intensiveon-siteconstructiontofactory-controlledfabricatedassem-bliescanreduceon-sitepollutionandincreasetheuseofcircular,recyclablecomponents.>Anindustry-wideeffortisneededtoreducematerialconsumption,optimisestructures,anddesigncustomisedpartsthroughpre-fabricationanddigitisedconstruction,whichproducesaninventoryofcircularcomponentsforfuturedisassemblyandre-use(seeBox5.1).>Standardsneedtorelyonperformance-basedmetricsratherthanprescribingoutmodedconventions,sothatcementproductioncanbeadaptedtolocalneeds(Scrivener,JohnandGartner2018).Improveconcretethroughcarboncaptureandstorage,whichhaspartialfuturepotential>Capturingandstoringcarbon(eitherundergroundorwithinmaterialstoenhancematerialstrength)iscriticaltoreduceemissionsfromcementproduction.>ToachievetheInternationalEnergyAgency’sscenariofornetzeroemissions,around95percentofCO2emissionsfromcementwouldneedtobestoredby2050,upfromjust5percentby2030(IEA2022a).Currently,lessthan0.1percentofallglobalemissionsarecapturedandstored.>BecausetheCO2streamneedstobealmostpuretostoreitcosteffectively,researchisurgentlyneededonmoreviablemethodstoscaleupcarboncaptureandstorage(seeBox5.2).>Carboncaptureandstoragecannotbetheonlyanswer.Relyingsolelyonimprovementsinthesetechnologieswithinthecementandsteelindustrieswillrequirea14,000percentincreaseincarbonstoragecapacityby2050;meanwhile,inthelast10years,theworldhaswitnesseda30percentreduction,ratherthanincrease,incarbonstoragecapacity(GlobalCCSInstitute2020)Urgentlyinnovatecementandconcreterecycling>Currently,lessthan1percentofconcreteismadefromrecycledmaterials(Caoetal.2020;PamenterandMyers2021).>Designforcircularrecyclingandreusehaslaggedinthecementandconcretesector,evenasthesematerialshavedisproportionateimpactsonoperationalcarbonacrossmanyclimates.47BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREBOX5.1ON-SITEPRE-FABRICATIONOFMODULARCONCRETECOMPONENTSINBOTSWANADDesignoptimisationofmodularcomponentscangreatlyreducetheuseofconcreteforenvironmentalcontrolsystems,leadingtoenergysavingsandfuturecircularity.ArchitectsandengineersfortheBotswanaInnovationHubhavedevelopedmethodsforcreatingprefabricatedmodularconcretecomponentsusinganon-site“mobilefactory.”Theseincludehollow-coreconcreteslabsforbuildingsthatgreatlyreducetheamountofsteelandequipmentneededforductingandenvironmentalcontrolsystems(seeFigure5.7).Theslabscouldleadtooperationalenergysavingsinbuildingsof20-50percentandtoreducedpeakcoolingloadsof70-90percent.Computeraideddesigngreatlyaidedthematerialoptimizationateverystepofthelifecyclefromdesigntodeliveryoffullyautomated,paperless,direct-to-fabricationtechniquesfortheconstructionoftheconcretebuildingenve-lopemodules.Concreteasamaterialchoiceisfurtherjustifiedinthisexampleasitsupportstheplantingofsubstantialgreenroofswithnativefloraandfaunathatadaptandco-existonthesiteandareabletoretainsubstantialwaterandbiodiversity.Theadditionallivingbiomassfurtherdramaticallylowersthebuildingcoolingrequirements,andthusitsoperationsenergyexpenditures.Theprefabricatedconcretemodulesalsocontainthemouldingofinteriorchannelsforallofthesystemstotravelthroughtheslab,whichnotonlyreducesmaterialsrequired,butenablessystemstobemorespaceefficient,reducingtheoverallvolumesrequiredbythebuilding.Thiscouldrepresentaverysubstantialsavingsonstructuralmaterialrequirements,especiallyfortallerbuildingssuchastowers,wherethestructuralmaterialstoresistwindloadsincreaseswithheight.5.7Creationofhollow-coreconcreteslabsatBotswanaInnovationHubDesignoptimisationofmodularcomponentscangreatlyreducetheuseofconcrete.Source:FromToptoBottom:BotswanaInnovationHub(SHoPArchitects;BuroHappoldConsultingEngineers);RightCenter:VortexExtruderon-site“mobilfactory”;LeftCenter:Pre-fabricatedmodularhollowcoreconcrete(Spiroll);Bottom:SchemeofaTermodeckslab(Spiroll)48BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE©KaterynaBabaieva/Pexels5.3SteelKEYMESSAGESteelisanindispensableconstructionmaterialtodayandacriticalcomponentofbuildingandtransportinfrastructures.However,evenwiththeemergingshiftamongsomesteelproducerstowards100percentrenewableenergyintheproductionphase,andalthoughsteelisverywellsuitedtorecycling(potentiallyreducingupto75percentofembodiedcarbon),thehighestgoalistoavoidtheuseofsteelinbuildingswherepossibleandtoshifttoprovenlow-carbonalternatives,sincesteelisanon-renewablematerialanddemandisincreasinglyoutpacingthesupplyofrecycledsteelsources.GlobalSteelUseinBuildingsandInfrastructureIsRisingMorethanhalftheworld’ssteelisusedintheconstructionofbuildingsandinfrastructure.Steelisthesecondmostabundantmaterialusedinbuildings,at360milliontonsin2008(Cullen,AllwoodandBambach2012).Itisperhapsthebuildingmaterialthatismostassociatedwithmodernisationandisaculturalindicatorofeconomicprogress,givenitsroleindevelopinginfrastructure.Annualsteelproductionin2021was1,950millionmetrictons,withcurrentgrowthratesofaround3percent(WorldSteelAssociation2022).Productionisanticipatedtoincreasesubstantiallyby2030(IEA2020).Ofthetotalironandsteelproducedworldwide,55percentgoesintothebuiltenvironmentsector,splitacrossbuildings(33percent)andinfrastructure(22percent)(Cullen,AllwoodandBambach2012).Incommercialandtallbuildings,steelisusedfortheprimarystructureaswellastoreinforceconcrete.Itisalsousedwidelyastheprimarymaterialforfittingoutmechanicalsystemsforheating,ventilationandcooling(HVAC).Asaprimaryandpreferredstructuralbuildingmaterial,steelcombinestensilestrengthwithlowcost,butitcanalsocomewithahighhumancost.Therearemanypointsofpotentialforcedlabouralongthesteelsupplychainduetothehazardousconditionsandlackoftransparency,rangingfromextractionandsmeltingtoproduction,rollinganderecting(GraceFarmsFoundation2022).Steel49BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE5.8ThetimedelayintherecyclingofmetalsThelonglifetimeofsteelproductshaslimitedtheamountofscrapavailable.Note:Mostmetalshaveanaveragelifetimeofaround20yearsbeforetheybecomeavailableforrecycling,andevenlongerwhenusedinbuildings.Theselonglifetimescombinedwithhighgrowthratesinthepastexplainwhymetalswillcontinuetobemadeprimarilyfromvirginmaterialsratherthanfromscrap.Source:UNEP2011.©DvoinikCIRCULARSTEELSteelIsEmissionIntensive,DrivenbyBlastFurnaceTechnologyUnlesspoliciesincentivisegreatermaterialeffi-ciency,coststructureswillfavourusingmorematerial.Theironandsteelsectorisenergyandemissionsintensive,accountingfor8percentofglobalfinalenergyuseand7percentofdirectenergy-relatedCO2emissions(IEA2020).Insteelproduction,mostemissionsaregeneratedduringthreeprocesses:whensteelisproducedfromprimaryrawmaterials(usingablastfurnaceorbasicoxygenfurnace),whencarbonisneededasareducingagent(providedascokederivedfromcoal,releasingCO2)andfromtheenergyusedtoheatthemelt.Anumberoftechnicaloptionsexistforincreasingthemate-rialefficiencyofsteel(therebyreducinguseandoverallemis-sions).Theseinclude:adoptinglightweightdesign,reducingyieldlosses,divertingmanufacturingscrap,re-usingcomponents,creatinglonger-lifeproductsandintensifyingsteeluse(Allwoodetal.2013;Raabe,TasanandOlivetti2019).Anexampleforextendingthebuildinglifetimeisusinggalva-nisedsteelforrebarinconcrete,sincegalvanisingprotectsthesteelfromcorrosionandthereforeavoidingtheriskoffailure.However,unlesspoliciesincentivisegreatermaterialefficiency,existingcoststructureswilltendtofavourmorematerialoverlesslabour(Allwood2013).Therearetwomainapproachestoreducecarbonemissionsfromsteelproduction:1)tocontinueusingcarbon-basedmethodsbuttocouplethiswithcarboncapturetechnolo-gies,and2)toreplacethecarbon(coke)usedinreduction,thechemicalconversionofironoreintopigiron,withalter-nativereductantssuchashydrogenordirectelectrolysis(Rissmanetal.2020).Movingtorenewableenergysourcesinproductionoffersthegreatestpotentialtoreducetheembodiedcarbonofsteel(Raabe,TasanandOlivetti2019).MakingSteelFromScrapWillReduceEmissions,ButRecyclingRatesAreAlreadyHighMakingsteelfromscrapsaves60-80%energy,butthescrapsupplyislimited.Analternativewaytoproducesteelisbyusingscrapasarawmaterial(“secondaryproduction”),whichoccursinanelectricity-poweredelectricarcfurnace.Producingsteelfromscraprequires60-80percentlessenergythanprimarysteelproduction(UNEP2013;IEA2020)anddoesnotentailchemicalreduction(hencenoinputofcoke,orheatedcoal).Thesemassiveenergysavingsalsoresultincostsavingsforproducers;thus,theuseofscrapasaninputmaterialisalreadyveryhigh,leavingonlymodestroomforimprove-ment.Incertainmarkets,steelisalreadybeingrecycledatover90percent(IEA2020).Thebiggestchallengetowideruseofsecondarysteelproductionisthelimitedamountofscrap.Alargegapexistsbetweenthesupplyofrecycledmaterialandrisingdemand.5.3.3t1t2TimeFlowTotalﬂowintouseFlowfromrecycling50BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE5.9CircularSteel—BarclaysCenter,BrooklynNewYorkTheFigureaboveshowsacontemporarydigitiseddesignandmaterialcomponenttrackingprocessforthesteelcomponentsofasportsarenainBrooklyn,NewYorkCity.Theabilitytotrackmaterialsandtheirassembliesbydigitisingallphasesofthelifecycle,fromdesignconceptionthroughconstructionmanagementandreusethroughaBuildingInformationModel(BIM)isenablingdecarbonisationstrategiesonmanylevels,frommaterialoptimisation,increasedproductivityateverystage,designfordisassemblyandreassembly,andreductionofon-siteemissionsthroughprefabricationofcomponents.Credit:ThorntonThomasettiConsultingEngineers,SHoPArchitectsKEYSTEPSTOWARDSDECARBONIZINGIRONANDSTEELImprovethequalityandcollectionmethodsofscrapsteel>Inacircularsteeleconomyusingonlyscrap,measureswouldbeneededtominimisecontamination.>Asmorescrapisusedinmetalproduction,concernsaboutthequalityofrecyclablesincrease,withcoppercontaminationbeingofhighestconcern(Daehn,SerrenhoandAllwood2019;Cooperetal.2020).>Measurestominimisecontaminationincludedesignforrecycling,bettersortingandthedeploymentofscraprefiningtechnologies(Cooperetal.2020).Improveproductionwithdirectreducedironoretechnologyandrenewableenergy>Transitioningallsteelproductiontobestavailabletechnologiescansaveupto26percentenergy;betterboilerscansaveupto10percent,andusingheatexchangersinrefiningcanreducepowerdemandby25percent(Nappetal.2014;GonzalezHernandez,PaoliandCullen2018;Fennelletal.2022).>Primarysteelproductionthroughthedirectreducedironprocessfollowedbyanelectricarcfurnaceavoidstheneedforcokeasareducingagent,leadingtoareductionof61percentincarbonemissionsifmethane-derivedgasandrenewableenergyareused,respectively(Fennelletal.2022).>Usingonlyhydrogenforthedirectreducedironprocesscouldreduceemissionsby97percent(Fennelletal.2022),butthiswilldependonaccesstocompetitivelypricedgreenhydrogen,whichislimitedinsupplyandfacesupscalingchallenges(Castelvecchi2022;Odenwelleretal.2022).Avoidoveruseofsteelbyselectingtheappropriateproductforthebuilding’slifetime>Materialsneedtobeselectedwiththeentirebuildinglifetimeinmind,notjusttheproductionstage.>Carbonsteelsarethedefaultmetalofchoiceforreinforcedconcreteandasstructuralmaterials.>Usingcorrosion-resistantstainlesssteelsinmarineenvironmentsmakesitpossibletodesignforlongerbuildinglifetimes,avoidingcostlyandcarbon-intensivemaintenanceandrepair.Correctmaterialselectioninmarineenvironmentsiscriticalbecausemosturbangrowthwilloccuralongcoastlines.>IntheInternationalEnergyAgency’smostambitiousdecarbonisationscenario,extendingthelifetimeofbuildingswouldcontributetomorethan90percentoftheCO2emissionreductionsforbothsteelandcementby2060(IEA2019).>Avoidingoverspecificationisakeyopportunitytominimisematerialuse,bothinmaterialselectionandintheamountofmaterialused.Forexample,thereisnoneedtousecorrosion-resistantstainlesssteelrebarforinlandapplications.Asaresult,35percentofallsteelismadefromscrap(WorldSteelAssociation2023).Thereasonsforthelimitedamountofscraparethelonglifetimeofsteelproducts(20yearsormoreinbuildings),combinedwiththerapidgrowthindemandinrecentdecades(seeFigure5.8).Aslongasdemandcontinuestorise,thegapbetweenscrapsupplyanddemandwillfurtherwiden,preventingthemajorcarbonbenefitsfromusingscrapratherthanvirginmetal.Thisconceptalsoappliestolong-livedmaterialssuchasconcrete,plasticsandglass.515.4AluminiumKEYMESSAGEAluminiumproductionishighlyenergyintensivewhenproducedfromores,whereasproducingaluminiumfromscrapcanreducetheenergydemandby70-90percent.Bringingthealuminiumsectoronapathtonearnet-zeroemissionsispossiblethroughacombinationofactions,mostimportantlyswitchingtolow-carbon(renewable)electricity,deployingnear-zero-emissionrefiningandsmeltingtechnologies,improvingthesortingofscrap,designingalloysforrecyclabilityandreducingdemandthroughmaterialefficiency.AluminiumHasWide-RangingApplicationsinBuildingsandConstructionThebuildingsandinfrastructuresectorusesmorethanaquarterofallaluminiumproduced.Withamarketshareof25percent,thebuildingsandconstructionsectorwasthelargestend-usesectorforaluminiumin2020,using21milliontonsofaluminium(CRUConsulting2022).Inconstruction,aluminiumisusedforroofingandcladding(37percent),windowsanddoors(27percent),curtainwalls(18percent)andothercomponents(18percent)(AllwoodandCullen2012).Aluminiumisproducedusingbothprimaryminedmaterialsand(toalesserextent)aluminiumscrap,whichconsistsofbothend-of-useandnew(industrial)scrap.Thevolumesofindustrialaluminiumscraparecurrentlymuchhigherthanforotherengineeringmaterials,indicatingthepotentialforsubstantialimprovementsinthematerialefficiencyofaluminium(CullenandAllwood2013).AluminiumfromPrimaryMinedOresIsExtremelyCarbonIntensiveSwitchingfromfossilfuelstohydrogenandnearzero-emissionelectricityisakeypriorityforalow-carbonaluminiumfuture.In2021,aluminiumproductioncontributedover3percentoftheworld’sdirectindustrialCO2emissions(IEA2022c).Producingaluminiumrequiresrefiningthebauxiteoreintoaluminaandsmeltingitintometallicaluminium,thelatterbeingbyfarthemostenergy-intensivestep,accountingforthree-quartersoftheenergyused(Gutowskietal.2013).Inprimaryaluminiumsmelting,electricityaccountsfor81percentofthegreenhousegasemissions(MissionPossiblePartnershipandIAI2023).DecarbonizingaluminiumwillAluminium©PhonlamaiPhoto/iStockPhoto5.10Sharesofprimaryandrecycledaluminiumsince1950,andprojectionsthrough2050By2050,theshareofscrapinaluminiumproductionwillberoughlyequivalenttothatofprimaryore.Source:IAI2021.KEYSTEPSTOWARDSDECARBONIZINGALUMINIUMPrioritisetheuseofsecondaryaluminiumandincreasescraprecycling>Usingonlyscrapratherthanprimaryorecouldreducetheembodiedenergyofaluminiumby70percent(whenconsideringtheprocessingofscrap)to90percent,amuchhighersavingspotentialthanforsteelorcopper(Allwoodetal.2019;Raabeetal.2022).>Advancedandmachine-learning-assistedscrapsortingandseparationtechniquescanimprovethescrapqualitybyreducingimpurities(Raabeetal.2022).>Accesstoscrapwilldifferamongregions,asdevelopedcountrieshavelargein-usestocks,whiledevelopingcountrieshavetobuildmostoftheirstocksfromprimaryaluminium(Liu,BangsandMüller2013).Improvematerialefficiencyanddesigntoreducethedemandforprimarybauxiteore>Materialefficiencystrategiescanreducethetotaldemandforaluminium,thereforeincreasingtherelativesharethatisproducedfromscrap.>Strategiesincludeincreasingyieldsinfabricationandmanufacturing,increasingend-of-liferecycling,improvingthequalityofscrapthroughbettersorting,andimprovingproductdesign(designingforbetterrecyclabilityandforreducedmaterialusewhiledeliveringthesameservices).Designaluminiumalloyswithrecyclinginmind>Withmostaluminiumbeingusedinalloyedform,animportantpathwaytowardscircularityandlowerembodiedcarbonisdesigningalloysthataremorescrap-tolerantthancurrentalloys.>Forevengreaterimpact,researchanddevelopmentareneededinanewgenerationofleanalloysthatcontainfewerimpuritiesandthereforefacilitaterecycling(Raabeetal.2022).Shiftaluminiumproductiontorenewableelectricitysources>Low-carbonelectricitysourcesareessentialforfurtherdecarbonizingaluminiumproduction.>Starkregionaldifferencesexistintheelectricitymixusedforaluminiumsmelting.InNorthandSouthAmericaandEurope,sharesofhydropowerandotherlow-carbonsourcesexceed75percent.Meanwhile,coaldominatesinAsia(90percent)andOceania(70percent)(IEA2022c).5.9Historicandprojectedglobalaluminiumproductionbysource(2000-2030)Globally,theshareofaluminiumfromscrapisincreasing.Source:Raabeetal.2022.requirenearzero-emissiontechnologiesforrefiningandsmelting,switchingfromfossilfuelstonearzero-emissionelectricity,andhigherrecyclingrates(currently70percent)(IEA2022c).SuppliesofAluminiumScrapAreLimitedButIncreasingEvenifallaluminiumwererecycled,thisscrapwouldonlyreplacelessthanhalfofcurrentdemand.Primarybauxiteorecontinuestobethemainrawmaterialinaluminiumproduction,althoughtheshareofsecondaryscrapisincreasing(seeFigure5.9).In2019,34percentofalumi-niumwasproducedfromscrap(IAI2021).Aswithsteel,scrapsuppliesarelimitedduetorapidgrowthandlonglifetimes(over20years).Evenifallend-of-lifealuminiumwererecy-cled,thescrapwouldonlyreplacelessthanhalfoftoday’saluminiumdemand(demandin2020wastwicethatof2000).By2050,theshareofscrapinaluminiumproductioncouldequalthatofprimaryore(IAI2021),evenasproductionconti-nuestorise(seeFigure5.10).Ifthedemandforaluminiumwerereducedthroughmaterialefficiencymeasures,itcouldrepresentanevenhighershare.5.3.2ENDOFLIFEGlobalAluminiumProductionEmbodiedEnergy(kWh/kg)Milliontons/year020002030Steel9%Copper50100150PrimaryAluminiumScrapSecondaryScrapPrimaryOreSecondaryScrapPrimaryOre5.3.3ShareofPrimaryandRecycled(%)AluminiumIngotProduction(Mt)201950197019902010203020504060801004080120160200Recycled%AluminiumproductionMTPrimary%535.5PlasticsandPolymerCompositesKEYMESSAGEPlasticsareeverywhereandexistinmanygradesandevenmorechemicalcompositions.Whileadditivesoptimisetheuseofplasticsinproducts,theyalsogreatlycomplicaterecycling.Polymersusedinbuildingsaspipingorwindowframesarerarelyrecycledattheirend-of-use.UseofPlasticsinBuildingConstructionIsIncreasingRapidlyUseofplasticsandpolymercompositesisprojectedtomorethandoubleby2060.Plasticsandpolymercompositesareubiquitousmaterialswhoseusehasskyrocketedsincethemid-20thcenturyandisprojectedtomorethandoubleby2060(OECD2022b).Plasticsarepopularduetothelowcostandeaseofmanu-facturing.PlasticsproductionoccursaroundtheworldbutisexpectedtogrowespeciallyrapidlyinAfrica,IndiaandtheMiddleEast(seeFigure5.11).IntheUnitedStatesofAmerica,buildingsandconstructionaccountedfor16percentoftotalplasticsusein2015(Dietal.2021).However,thisfiguredoesnotaccountforalltheplasticsusedintheinteriorfurnishingsandfinishesofbuildings,whichalsocanposerisksforthehealthandwell-beingofinhabitantsfrommaterialoutgassing.5.11Totalplasticsproductionbyregion,1980-2060PlasticsproductionisexpectedtogrowrapidlyinAfrica,IndiaandtheMiddleEast.Source:OECD2022b.GlobalPrimaryPlasticProduction(Mt)GlobalPrimaryPlasticProductionbySector50019501955196019651970197519801985199019952000200520102015100150200250300350400450BuildingandConstructionOtherTextilesIndustrialMachineryConsumer&InstitutionalProductsElectrial&ElectronicTransportationPackaging©KrishnaviHardware54PlasticsandPolymerComposites5.12EndusesofpolymersforthebuildingsandconstructionindustryMostplasticsareusedinthebuildingsectorforpipes,windows,insulation,liningandcoverings.Note:ThefigureshowsthemostlywidelyusedplasticpolymersintheUSA(left)andEurope(right).PP=polypropylene,LDPE=low-densitypolyethylene;HDPE=high-densitypolyethylene,PET=polyethyleneterephthalate,PVC=polyvinylchloride,PS=polystyrene,EPS=expandedpolystyrene.Source:Dietal.2021;Kawecki,ScheederandNowack2018.IntheU.S.constructionsector,themostwidelyusedplasticpolymerisPVC(polyvinylchlorideor“vinyl,”usedmostlyforpipingandwindowframes),followedbyhigh-densitypolyethylene(HDPE,usedinbuildingenvelopes)(seeFigure5.12left)(Dietal.2021).InEurope,mostoftheplasticsusedinbuildingsareforpipes(mostlyPVCbutalsoHDPEandpolypropylene),followedbywindows(PVC),insulation(expandedpolystyrene),linings,buildingtextilesandpacka-gingfilms(seeFigure5.12right)(Kawecki,ScheederandNowack2018).Withawidespreadtransitiontobio-basedmaterialcomposites,theuseofpolymericbindingagentswouldincreasedramatically.Thiswouldrequireamassiveincreaseinfundingforlow-carbonpolymersthatarebiocompatibleandbio-based.TheCarbonIntensityofPlasticsVariesbyType,andEmissionsAreRisingToreducecarbonemissionsfromplasticsrequiresreducingthegrowthrateofthesectorbyhalf.Plasticsaccountedfor3.4percentofglobalgreenhousegasemissionsin2019,andplastics-relatedemissionsareexpectedtomorethandoubleby2060(OECD2022a;OECD2022b).Around61percentofemissionsfromplasticsaregeneratedduringresinproduction,30percentduringconversionprocessesand9percentduringend-of-useprocessing(seeFigure5.13)(ZhengandSuh2019).Emissionsarelowestduringlandfillingbecauseplasticsdonotdegrade–andthereforedonotcontributetolandfillemissions–formanydecades.Thecarbonintensityofplasticsvariesbytype,withtheemissionsfromcarbonfibresbeingfour-foldhigherthanthosefromthetypicalresinsused(Nicholsonetal.2021).Largereductionsinthecarbonimpactofplasticsarepossiblethroughintegratedenergy,materials,recyclinganddemand-managementstrategiestocurblife-cycleemissions.Onestudyestimatedthattokeepplastics-re-latedemissionsin2050near2015levels(thusavoidingtheprojectedfour-foldincrease)wouldrequiremajorshiftstowardsbio-basedplastics,renewableenergyinproduction,andrecycling,aswellasreducingtheglobalplasticsgrowthratefrom4to2percent(ZhengandSuh2019).5.4.2ConstructionPipesNon-consumerﬁlmsOtherconsumerpackagingOthernon-consumerpackagingConsumerbottlesConsumerbagsClothingConsumerﬁlmsHouseholdplasticsOthernon-textileproductsHouseholdtextilesAgriculturalﬁlmsFurnitureHygieneandmedicaltextilesNon-consumerbagsTechnicalclothingOthertechnicaltextilesMobilitytextilesAgrotextilesAgriculturalpackagingﬁlmsAgriculturalpackagingbottlesGeotextilesPersonalCareandCosmeticProducts(PCCP)AgriculturalpipesAgriculturalotherTechnicalhouseholdtextilesFabriccoatingsElectricalandElectronicEquipment(EEE)AutomotiveWindows,Proﬁles,FittingsConsumption(kt)ExamplesofEndUsesforPlasticsinBuildingsPlasticswithEndUseinBuildingsandConstructionintheUSin2015inEuropein2017BuildingsandConstructionPackagingElectricalFurnitureandFInishingsCosumerProductsIndustrialAdhesives,Ink,CoatingsOtherTransportInsulationCoveringsLiningsBuildingTextilesConstructionPackagingFilms010002000LDPEHDPEPPPSEPSPVCPETother16%55BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURERecyclingRatesofPlasticsAreVeryLowandAreNotProjectedtoIncreaseSubstantiallyGlobally,theaverageplasticsrecyclingrateisonlyaround9%.Recyclingoffersanopportunitytoreducethedemandfornewpetroleum-basedplastics.Yettheaverageend-of-liferecyclingrateisonly9percent(Geyer,JambeckandLaw2017;OECD2022a),leavingmuchroomforimprovement.Plastics’lowcost,easeofmanufacturingandtunabilityhaveresultedinaplethoraofchemicalcompositionsthatposetechnologicalchallengesduringrecycling.Theseincludeconcernsaboutthequalityofthefeedstock(giventhethou-sandsofmonomers,additivesandprocessingaidsused)(Wiesinger,WangandHellweg2021),colour,contaminationanddegradationofphysicalproperties.Strictregulationsforfood-gradeapplicationsalsolimittheuseofrecycledplastics.Mechanicalrecyclingisthedominantrecyclingtechnologyforplasticsandentailsaseriesofseparationsteps,followedbymeltingandreprocessing.Novelwaystocomplementmechanicalrecyclingincludesolvent-basedrecycling(puri-fication),chemicalrecycling(depolymerisation,solvolysis)andchemicalrecovery(thermochemicalconversionsuchaspyrolysis,gasification).However,technologiesarehighlyplastic-specific–requiringstrictsortingmethods–andindustrialimplementationandeconomicandecologicalevaluationsaremostlypending(ThiounnandSmith2020;Hofmannetal.2020).5.13Life-cyclegreenhousegasemissionsfromtheplasticssector,2015Themajorityofplastics-relatedemissionsaregeneratedduringresinproduction.Note:Thefigureshowsgreenhousegasemissionsbyplastictypeandlifecyclestage.Thecarbonimpactishighestduringresinproductionandlowestduringlandfilling.PP=polypropylene,LDPE=low-densitypolyethylene;HDPE=high-densitypolyethylene,PET=polyethyleneterephthalate,PVC=polyvinylchloride,PS=polystyrene,EPS=expandedpolystyrene,PUR=polyurethane,PP&A=polyphthalamide.Source:ZhengandSuh2019.KEYSTEPSTOWARDSDECARBONIZINGPLASTICSANDPOLYMERSReducethedemandforvirginplasticsbyincreasingrecyclingandimprovingcollectionandsorting>Recyclingplasticsoffersanopportunitytoreducethedemandforpetroleum-basedplastics.However,plasticsrecyclingfacessubstantialtechnologicalandlogisticalchallenges.>Bettercollectionandsortingcanbeencouragedthroughbothmarketincentives(suchasgreaterrecycledcontent)andregulatoryincentives(suchasannualincreasesinrecoverytargets).>Forwindows,collectionschemesshouldfocusonthecombinedrecoveryofwindowglassandframematerials(PVC,aluminium,wood)andoff-siteproces-singtominimiseglasscontamination.Shiftfromfossil-basedtobio-basedfeedstockstoreduceemissionsfromplastics>Bioplasticsareeitherbio-based,biodegradable,orboth,withamarketshareoflessthan1percentin2021;onlyaround50percentofbioplasticsarebiodegra-dable(EuropeanBioplastics2022).>End-of-lifemanagementofbio-based,non-biode-gradableplasticsisofconcernsincelandfillingorincinerationwouldleadtogreenhousegasemissions,negatinganyupfrontcarbonsequestrationbenefits.>Duringthetransitionfromfossil-basedtobio-basedplastics,theircombinedappearanceinrecyclingstreamswillfurthercomplicatesortingandrecycling.>Misunderstandingsaboutthe(bio-)degradabilityofplasticscouldleadtoanincreaseratherthandecreaseofplasticsintheenvironment(AlbertssonandHakkarainen2017),asbio-degradationdependsoncontrolledindustrialcompostingconditionsandwouldnotapplytoplasticlitterintheenvironment.Simplifythechemicalcompositionsofplasticstofacilitategreaterrecycling>Today’splasticsarebasedonmorethan10,000monomers,additives,andprocessingaids,withnearlyaquarterofthemofpotentialconcern(Wiesinger,WangandHellweg2021).Recyclingishinderedbythecomplexityinproductcompositionsandalackofinformationonsubstanceproperties.>Designingplasticsforthecirculareconomyaddressesalllife-cyclestages,fromcircularpolymerdesign(Sobkowicz2021)tosourcing,manufacturing,useandend-of-use(OECD2021).LandﬁllRecyclingIncinerationGlobalLifecycleGreenhouseGas(GHG)EmissionsofPlasticsin201591%RESINPRODUCTION61%ENDOFLIFEPRODUCTIONCONVERSION30%OthersOthersAdditivesAdditivesPVCPVCPSPSHDPEHDPEPETPETL/LLDPEL/LLDPEPURPURPPPPPP&APP&A5.4.1ENDOFLIFE9%56BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE5.6GlassKEYMESSAGEToreducetheembodiedcarbonofglass,asetofactionsisrequired.Theyincludeshiftingenergy-intensiveglassproductiontobestavailabletechnologiesandlow-carbonenergysources;establishingapolicyframeworkthatincentivisesflatglassrecyclingfrombuildingsthroughlocalsolutionsthatavoidcontaminationofrecyclingstreams,anddesigningglassthatminimisesunwantedheatabsorptionintotheinteriorandinsteadcapturessolarenergyforheating,coolingandlighting.DemandforGlassinConstructionandRenovationIsRisingThebuildingssectoristhesecondlargestenduserofglassafterpackaging.Theglasssectorisdividedintoflatglass(51percent;forbuildings,automotiveandelectronics),containerglass(45percent;forfoodandbeverages)andotherglass(4percent;e.g.,domesticglassandtableware)(InternationalYearofGlass[IYOG]2020).Thebuildingssectoraccountsforaroundtwo-thirdsofflatglassproduction,withglassusedinmostbuildingfaçadesaswellasinmanyinteriorapplications.Around60percentoftheworld’sflatglassmanufacturingcapacityisinChina(IYOG2020).GlassisEnergyIntensivetoProduceandInvolvesEmissionsTrade-offsMulti-panedwindowssaveenergyduringoperationsbutaremoreenergy-intensivetoproduce.Glassproductionisahigh-temperature(between1,400and1,600degreesCelsius),energy-intensiveprocessthatisresponsiblefor0.3percentofglobalcarbonemissions(86millionmetrictons)(Westbroeketal.2021).Glassproductionreached209millionmetrictonsin2019andisgrowingrapidlyat5.2percentannually(IYOG2020).Therawmaterialsforvirginglassproductionaresand,limeorcalciumcarbonate,andsodaash.Miningthesematerialsposesahighriskofforcedlabour(GraceFarmsFoundation2022).MeltingtherawmaterialsforglassleadstotwomainsourcesofCO2emissions:1)energyemissionsfrommeltingand2)processemissionsfromaddinglimestoneandsodaashtothemelt(Westbroeketal.2021).Theenergyintensityofproductiondependsgreatlyonthetechnologyandfuelsourceused.©IlyasYasinUslu/Shutterstock57BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREGlassGlassisamongthemostcontroversialbuildingmaterials,withtrade-offsbetweenembodiedandoperationalemis-sions.High-efficiencywindowswithdoubleortriplepanesprovidesubstantialenergysavingsduringtheoperationofbuildingsbutaremoreenergyintensivetoproduce.Glasscoatingsreduceoperationalemissionsbyprovidingshadingandreducingtheneedforartificiallighting(ArupandSaint-GobainGlass2022),buttheycomplicaterecyclingwiththeircomplexmaterialcomposition.Variationsindesignandexpectedbuildinglifetimesgreatlyinfluenceemissionsovertheglasslife-cycle.Atthemanufacturingandusephases,themostpromisingmeasuresforimprovingthematerialefficiencyofglass(andthusreducingemissions)arethere-useofcontainerglass(68percentre-usebringsemissionsavingsof38percent),usinglessmaterialinthedesignofcontainers(10percentreductioninmassbrings6percentemissionsavings)andextendingthelifespansofbuildingsandvehicles(Westbroeketal.2021).HardlyAnyGlassintheBuiltEnvironmentIsRecycledRecyclingisapowerfulbutunderusedtoolfordecarbonizingglass,particularlyinthebuildingssector.Glassisamaterialthatintheorycouldbeproducedinalow-carbonmannerandbeinfinitelyrecyclable.Inpractice,onlyathirdofcontainerglassandhardlyanyflatglassisrecy-cled.Containerglass,usedmostlyforbeverages,typicallyfacesshortlifetimes(lessthanoneyear)andhaswell-esta-blishedrecyclingtechnologies;itsaveragerecyclingrateis32percentglobally,althoughinsomecountriesitreaches70percent(Westbroeketal.2021).Incontrast,flatglassisusedmainlyforbuildingswithlonglifetimes,estimatedat75years,delayingrecyclingopportunities(Westbroeketal.2021).Thelittleglassfromthebuiltenvironmentthatisrecycledisrarelyrecycledasflatglass;instead,afterremovalitisdowncycledforuseininsulation,containers,constructionaggregatesandroadpaint,amongothers(Westbroeketal.2021).InEurope,therecycledcontentofflatglassis26percent,butmostofitcomesfrompre-consumerscrap(GlassforEurope2020),aspost-consumermaterialcurrentlycannotreliablymeetthestrictqualityrequirementsinflatglassmanufacturing.Also,thehighweight-to-volumeratioofglassmakesitstransportcostly,withhighenvironmentalimpacts;forthisreason,itisimportanttosetuplocalandregionalrecyclinginfrastructures(BristogianniandOikono-mopoulu2022).KEYSTEPSTOWARDSDECARBONIZINGGLASSShiftglassproductiontolow-carbonenergysourcesandbestavailabletechnologies>Solutionsincludeswitchingtolow-carbonfuels,meltingusingrenewableelectricity,improvingenergyefficiencyinprocessingandoperations,andwasteheatrecovery(Zieretal.2021).>Analysisof16emergingglassproductiontechnologiesshowedpotentialenergysavingsof20-70percent(SpringerandHasanbeigi2017).>Largeregionaldifferencesinemissionsindicatethatashifttobestavailable(andemerging)technologiesisakeydecarbonisationtool(Scaletetal.2013).Provideincentivesforlocalproductionandrecycling>Usingrecycledglass(“cullet”)inglassmanufacturingcanreduceenergyuseinfurnacesby2.5to3percentforevery10percentofculletinput,ontopofthesavingsfromavoidedsodause(IEA2007)(or30percentifallglassweremanufacturedfromcullet).>Throughtheproperhandlingandrecyclingofbuildingglass,theEuropeanUnioncouldavoidthelandfillingof925,000metrictonsofglasswasteannuallyandsavearound1.23millionmetrictonsofprimarynon-renewablerawmaterials(Hestin,deVeronandBurgos2016).>Thesemeasuresrequireeducationandclosecollaborationofcontractorsandrecyclers,standardsandlegislationthatencouragesuchpractices(e.g.,landfilltax,incentivesforlocallybasedproductionandrecycling),rewardsforrecyclingandre-useincertifica-tionsystems,andfocusingsustainabilityassessmentcreditsystems(e.g.,BREEAM,LEED)onthere-useandrecyclingofglass.Improveglassrenovationanddemolitionpracticestomaintainqualityandenablerecycling>Increasingtheuseofflatglassculletrequiresensuringthattherecycledglassisclean,withonlyminimalcontamination(e.g.,nomixinginofspecialheatandfire-resistantglasstypeslikeCeran).>Discardedwindowsshouldbedisassembledoff-siteincleanenvironmentsthatallowforefficientseparationandforclosed-looprecyclingprocessesthatmaintainthehighqualityofflatglassandthere-useofcoatedglasswherepossible(GlassforEurope2013).>Glassrecyclingneedstobeoptimisedforthelocalcontext,balancingtheneedsforhighcollectionefficienciesandmaterialquality(Hestin,deVeronandBurgos2016).>Analternativeglassrecyclingpathproposesthelocal,low-techandcontamination-tolerantcastingofculletintovoluminouscastglasscomponentsforstructuralapplicationsinarchitectureandinteriordesign(BristogianniandOikonomopoulu2022).58BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE5.14AdvancedglassfaçadesGlassfaçadesofthefutureneedtocapturesolarenergyforuseinheating,cooling,lightingandelectricalloads.Duetoitstransparencyanddurability,glasshasauniquerelationshiptotheenergybalanceofbuildings:itcantransmitupto80%ofavailablenaturaldaylight,therebygreatlyboostingthehealthandwellbeingofoccupants,whileloweringelectricalloads,ithasalsobeenimplicatedindrivingupthecoolingexpendituresofbuildingthroughunwantedsolarheatgain.(althoughthiswouldgenerallybeanetpositiveincoldclimatesinthewinter).Infuture,inordertoreachnet-zerooperationalenergy,perthefigurebelow,glasswillbeaveryimportantmaterialforcombiningthecollectionofsunlightforbothdaylighting,heatingcoolingandelectricity,inordertooptimiseforallofthesefunctionssimultaneously.Source:Novellietal.2022.DAYLIGHTING&VIEWSCOLLECTION+CONCENTRATIONCOGENERATIONENDUSESImproveglassdesignandrelatedcomponentsbyadoptingbestavailabletechnologies>Typically,glassisnotusedonitsowninbuildingsbutisassociatedwitharangeofothermaterialsandcomponents.Thesupplychainsforglasscurtainwallsinparticularcanbecomplex.>Decisionsmadeduringthedesignstagecanhaveimpactsontheembodiedcarbonofglasssystems.Incentivesineducationandenforcementbybuildingcodeswouldgreatlyincreasetheavailabilityofcircularglass.>Incommercialbuildings,usebio-basedframingmaterials,suchasengineeredtimberorbamboo,ratherthanhigh-carbonmaterialssuchasaluminium.Improveglassdesignforwindowsandcurtainwallstooptimallyabsorb,storeandredistributesolarenergyforbuildingfunctions>GlassfaçadesoftendriveuptheenergydemandforcoolingGlassfaçadesoftendriveuptheenergydemandforcoolingbecausetheyeitherletintoomuchheatandglare(increasingthesizeandemissionsofcoolingequipment)ortheyreflecttheexcesssolarenergyontourbanpavements,worseningtheheatislandeffectanddrivingupcoolingloads.>Byusingbuildinginformationmodellinginthedesignphase,abuilding’sshapeandfaçadecanbedesignedtoletinmoresolarenergyduringcoldperiodsandremainself-shadedduringhotperiods.However,thesestrategiesarelimitedinhotclimates.>Farmoreresearchanddevelopmentisneededtoadaptglassfaçadestocapturesolarenergyforuseinheating,cooling,lightingandelectricalloadsinthebuildinginterior(seeFigure5.14).Glassiskeytothefutureon-sitesolarcollectiontechnologiesthatcanenablenetzerobuildings(Novellietal.2022).59BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE5.7MasonryandEarth-BasedMaterialsKEYMESSAGEImportantprogressisoccurringinthedecarbonisationofearth-basedmasonry,includingthroughtheuseoflow-carbonbinders,secondarycementitiousmaterialsandadmixturesthatresultinhigher-qualityproducts.However,scalingtheadoptionofthesematerialsaffordablyreliesonlocaladoptionofexistingstandards,certification(low-carboncredits)andcoordinatedupskillingofstakeholders.Decarbonisationofthebuildingsandconstructionsectorrequiresashiftawayfromtheuseofconventionalhigh-carbon,non-renewablebuildingmaterialsandtowardstheuseofrenewableandbio-basedmaterials.However,itisunrealistictoassumethatthesectorcanrapidlyandeasilytransitionto100percentrenewablebiomaterials.Duringtheinterimperiodandbeyond,itiscriticaltosupporttheconti-nueduseoflower-carbonnon-renewablematerialssuchasmasonryandearth-basedmaterials.TraditionalTechnologiesHaveProvenBenefitsbutHaveLostAppealinEmergingMarketsFormuchofhumanhistory,peoplehaveusedearth-basedmaterialsforload-bearingapplicationsinmasonryconstruc-tion,withsustainable,low-carbonmethods.Inthetraditionalcontext,thesematerialsaremadeon-sitebymixingclay-richsoil,naturalfibres,andwater,andlettingthemdryinhighoutdoortemperatures.Recyclingofnon-firedearth-basedmaterialsiscommonpractice,astheclaybinderscanbere-usedwithoutadditionalheatingorchemicaltreatment.Duetotheirhighthermalmass,earth-basedmaterialscanhavepositivebenefitsforpassivespaceconditioning,greatlyreducingtheoperationalcarbonofbuildingsincertainregions,particularlyaridclimates(seeFigure5.15).Giventheprojectedimpactsofclimatechangeinregionscharacterisedbyextremelyhighdaytemperatures(above40degreesCelsius)andcoldnights,passiveearth-basedsystemscouldhelpmediateharshclimaticpatterns.Onlyaround8-10%oftheworld’speoplecurrentlyliveinearth-basedstructures.Attheendofthe20thcentury,earth-basedstructureshousedaroundathirdoftheglobalpopulation;sincethen,thissharehasfallentoonly8-10percent,with20-25percentoftheuseoccurringindevelopingcountries(HoubenandGuillaud1994;MarshandKulshreshtha2022).Asincomeshaverisenandaccesstoconcretemasonryhasincreased,theuseofearth©TimUmphreys/UnsplashMasonryandEarth-BasedMaterialsasabuildingmaterialhasdeclined.Countrieswheremorethan10percentofthepopulationstilllivesinearth-basedbuildingsincludeBangladesh,theDemocraticRepublicoftheCongo,Ethiopia,India,Mexico,Nigeria,UnitedRepublicofTanzaniaandVietNam(MarshandKulshreshtha2022).Inmanydevelopingcountries,earth-basedmasonryisasso-ciatedwithpoordurability,poormoistureperformance,highmaintenanceandlowsocialclass.Inappropriateuseofthematerialforthelocalcontexthasinfluencedperceptions.Poorbuildingorientation,largewest-wallsurfaceareasandpoorcross-ventilationcanbringinefficienciesinheatgain/loss.However,acrossregions,andwithinhigh-endarchitecturaldesign,thereisrenewedinterestininnovatingearth-basedpracticeswithcontemporarytechniquesandstandards.Earthbrickproductioncanbeverylowcarbon,butitisatriskforpooron-sitelabourandenvironmentalconditions.Althoughthepotentialishightoincreasedevelopmentoflocallybasedsupplychains,theproductionofearth-basedmaterialscanhavenegativesocialimpactsifnotproperlyoverseen.Brickisoneofthemost-usedmaterialsatriskforforcedlabour,withmorethan20countriesidentifiedforabuseswithintheindustry(GraceFarmsFoundation2022).Childrenandadultsproducingbricksareoftenheldindebtbondageandbreathehazardousdustforprolongedperiods.5.15Climatetypesandthepotentialforearth-basedbuildingsEarth-basedbuildingshavehighpotentialtoreduceemissionsinaridandtemperateclimates.Note:Thefigureshowstheclimatetypeswhereearth-basedbuildingshavepotentialtodrivedownoperationalcarbonthrougheffectivepassivedesign.Source:Gupta2019.5.16ComparisonofthecarbonintensityandmechanicalperformanceofdifferentstabilisedearthmasonrytechnologiesStabilisationofearthmasonryusingPortlandcementmultipliesthecarbonintensityindex.Source:AdaptedfromVanDammeandHouben2018.ExistingearthenconstructionAridandtemperateclimatesAridandtemperateclimates+earthenconstructionoverlap5.6.2CarbonIntensities(kg.m-3.MPa-1)Compressivestrengh(MPa)10020401000kg/m3500kg/m3250kg/m3100kg/m3608010020304050StabilizedadobeStabilizedrammedearthStabilizedearthblocks61BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREBOX5.3GREENINGTHEMASONRYVALUECHAININWESTAFRICAWiththeiryoungpopulationsandgrowingneedforinfrastructureandhousing,developingcountriesinAfricarepresentthefutureinconcretemasonrydemand.WestAfricahastraditionallyimportedmostoftheclinkerandcementthatitusesforconcreteproduction,duetothelackofsuitablelimestonereserves.GiventhehighcarbonfootprintofconcretemasonrystructuresthatrelyonPortlandcementbinders,however,thedevelopmentandadoptionoflocal,low-carbonalternativesiskey.GhanahasthehighestuseofPortlandcementinsub-SaharanAfrica,at215kilogramsperperson(Harder2021).AcrossWestAfrica,reducingimportdependencethroughsubstitutionofPortlandcementwithearth-based,locallyavailablecementitiousmaterialsandpozzolanaresourceswillbekeytodrivingdownCO2emissionsandincreasingeconomicresilience(Bediako,AmankwahandAdobor2015).Already,leadingcementcompaniesinGhana,suchasSUPACEMandPozzomixCement,areusingcalcinedclaycementasanalternativetoclinker-basedcement.AdobeearthmasonrytechnologieshavealonghistoryinWestAfrica.Theyaretraditionallymadefromubiquitouslateritesoilscomprisingsand,clay,silt,andpebbles,sometimesmixedwithcowdungorfibrefromguineagrassstraw.Themodernversionofadobeisthecompressedearthbrick,producedusingchemicalstabilisationandcompactiontoimprovemechanicalperformance.Earthmasonryisbasedoncommunity-specificknowledgeaswellassmall-scaleindustrialmanufacturingofstabilisedearthblockproducts.ForcountriesthatsupplyWestAfricawithcement,suchasSenegal,usinglow-carbonfuelsinproductionandintegratingearth-basedmasonryproductsintothevaluechainiscritical.OneofSenegal’slargestcementcompanies,Sococim,isusingalternativefuelssuchasgroundnuthulls.SenegalisalsoexperimentingwithusingTyphaaquaticweedbiomasstodevelopearthmasonrywallsandroofingproductson-site(seeFigure5.17).5.17Compressedearthblockmasonrywallandon-sitemanufacturinginDakar,SenegalSenegalisexperimentingwithTyphaweedbiomasstodevelopearth-basedstructures.Credit:Worofila.©Worofila62BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREEmissionsfromEarth-BasedTechnologiesRisewithCement-BasedMortarsToimprovetheperformanceanddurabilityofearthmasonry,progresshasbeenmadeindevelopinglow-carbonbinders,surfacetreatmentsandadmixtures(chemicalsusedtoreducebinderandwaterdemandandincreasedurability)(VanDammeandHouben2018).Traditionally,materialstabilisationhasbeenachievedusingearthenplastersandstuccoesthatintegratearangeofplant-basedresins,gums,plantjuice,animaldungandfluids.Morerecently,theuseofPortlandcementtostabiliseearthblocksgreatlydrivesupemissions,withonlyminorperformancebenefitsthatcanalsobeachievedthroughlow-carbon,circularby-products(seeFigure5.16).Thus,thecarbonfootprintofearth-basedbuildingtechnologiesvariesdependingonthebinders,naturalfibresandadditivesused;onwhereproductionoccurs(on-oroff-site);andontheuseofcompactionorfiringtoimprovematerialstrengthanddurability.>Fornon-firedadobeearthblocksthatcureinthesun(madefromsand,claybinderandorganicmaterial),theembodiedcarboncanrangebetween1.2and5.4kilogramsofCO2perkilogramofearthblock(Illampas,IoannouandCharmpis2014;Christoforouetal.2016).>Forfiredclaybricks,thecarbonfootprintskyrocketsduetothehightemperaturesrequiredforclaysintering.Whenusinganaturalgas-firedkiln,theaveragecarbonfootprintisanestimated230-250kilogramsofCO2perkilogramofearthblock(KulkarniandRao2016).Thefootprintusinganoil-firedkilnis1.4timeshigher,near340kilogramsofCO2perkilogramofearthblock(VentaandEng1998).>Forrammedearthwallstructures–inwhichprocessedearthsoiliscompactedintosolidwallsusingtemporaryformwork–theuseofPortlandcementstabilisersandelectricandpneumaticrammingcangreatlyincreasecarbonfootprints(ReddyandKumar2010).Comparedtoconventionalconcretemasonry,adding5-10percentPortlandcementandlimetorammedearthstructuresledtohigherCO2emissionsandworseperformance(Scrivener,JohnandGartner2018).Thecarbonfootprintofstabilisationtechniquesmustbeweighedagainstthesusceptibilityofunstabilisedearthwallstomechanicalandmoisturedamageanderosion.InterestinModernEarth-BasedConstructionIsGraduallyIncreasingThestockofmodernearthenbuildingsisgrowing.Duetothehighqualityandappealofmodernearthenbuil-dings,theuseoflocalearthresourcesforbuildingisgainingrecognitionasa“niche,”reliableandattractiveoption(Swan,RteilandLovegrove2011;Niroumandetal.2017).Asaconse-quence,thenumberofinnovativeearth-basedproductsfromearthconstructioncompanieshasincreased(Leylavergne2012;MarshandKulshreshtha2022),ashastheworldwidestockofmodernearthenbuildings(Correia,DipasqualeandMecca2011).However,suchinitiativesarelimitedbythehighcostsofentrepreneurialexperimentationandearlyadoptionshoulderedbyclients.KEYSTEPSTOWARDSDECARBONIZINGEARTH-BASEDMASONRYImprovethedesignofearth-basedmasonryforlongevity,andprovidetechnicaltraining>Inthenearterm,effortisneededtowardsimprovingthelongevityofearthmasonrywithoutPortlandcement(Scrivener,JohnandGartner2018).>Technicaltrainingisneededonthedesigntoenhancethedurabilityofearthmasonryandpanelsystems.>On-sitetrainingandupskillingofarchitecture,engineeringandconstructionprofessionalsisneededtoencourageandnormalisethedesignandintegrationofearth-basedtechnologies.ShiftfromPortlandcementbinderstolow-carbonalternativesinearth-basedmasonry>Rapiddevelopmentisneededoflow-carbonbinders,naturalsupplementarycementitiousmaterials.>PromotealternativestoPortlandcementforbinders,suchaslow-carbonlime,alkaline-activatedmaterials,andgeopolymers,includingvolcanicpozzolan(Abidetal.2022;Kamwaetal.2022).>Promotebio-basedsupplementarycementitiousmaterialsincludingfusedlateriteandagriculturalandindustrialresidues,oftenavailablelocally(Adinkrah-AppiahandObour2017;Schmidtetal.2021).>Indevelopingcountrieswherelow-carbonbindersandcementitioussupplementsalreadyexist,incentivesandeducationareneededtostimulatemarketdemandandfinancingtoscaleadoption(seeBox5.3).Developlocallyadaptedstandardstoincreaseadoptionandaffordabilityofearth-basedmasonry>Incentivisestakeholderstocontinuetodevelopregionalandinternationalstandardsforearth-basedmaterialsthatcanbeintegratedintolocalandregionalbuildingcodesandmaterialstandards(CRAterre-EAG1998;NewZealandStandards1998;Vyncke,KupersandDenies2018;AfricaResearchandStandardsOrganisa-tion2018;Schroeder2018).Increaseeducationanddemonstrationtoboostsocietalandindustryacceptanceofearthbuildings>Incentiviseprofessionalstodevelopawarenessamongclientsandtobuildtheresearchcapacitytoaddressnegativeperceptionsandtechnicalchallenges.>Toincentivisetheadoptionoflow-carbon,earth-basedmaterials,educationontheirpositiveimpactsneedstobeextendedtobuildingownersaswellasfinanceandinsurancecompanies.>Educationontheappropriatedesignandintegrationofearth-basedmaterialsiscriticalforimprovingfurabilityandreducingoperationalcarbon,especiallyforhousingintropicalrainforestandsavannaclimates.63ConcreteSteelAluminiumPlasticGlassTABLE5.1SUMMARYOFDECARBONISATIONSTRATEGIESPERMATERIALNON-RENEWABLEMATERIALS>Improvequarryrehabilitationandbiodiversityrestorationoflandscapes.>Reducetheclinker-to-cementratiowithalternativematerials.>Userecycledaggregates.>Electrifykilnsanduserenewableelectricitysources.>Integratecarboncaptureandstoragetoprovideadditionalstrength.>Minimizewastewithcomputationaldesign-for-disassemblyandre-use.>Minimizeon-sitewasteandemissionsthroughpre-fabrication.>Educatebuildingdesignprofessionalsinmaterialefficiency,optimization.>Developstandardsandbuildingcodesthatrequiremodularconcrete.>Incentivizerenovationoverdemolitionandbuildingcodesforrecycled.>Shiftfromblastfurnacestodirectreducediron(DRI)technology.>Electrifyallsteelproductionmethodswithrenewableenergysources.>Reducesteelusethroughacombinationofmaterialefficiencymeasures.>Avoidusingnewsteelbysubstitutingwithre-used(best)andrecycledmaterials.>Shifttolow-carbonalternativessuchasbio-basedmaterialsifpossible.>Adaptbuildingcodestoavoidoverspecificationandoptimizestructures.>Designwithpre-fabricatedelementsfordisassemblyandre-use.>Includematerialefficiencytraininginthecurriculaofarchitectsandengineers.>Ensurethatstakeholdersacrossthevaluechainusethesamemetrics.>Improverecyclingmethodstoenabletherecoveryanduseofmoresteel.>Reducedemandfornewaluminiumbypromotingre-useandrecycling.>Useelectricityfromrenewablesources(includinghydropower).>Imposestrictregulationstodesignforthecircularityofcomponentparts.>Standardizealuminumalloys/componentsforre-use.>Avoidoverspecificationanduseofprimarysourcematerial.>Electrifyheavyconstructionandtransportequipment.>Specifyhigh-performancebuildingenvelopes.>Maximizerecyclingandinvestinalloy-specificsortingandrecycling.>Certifydisassembledandre-usedcomponents.>Avoidtheproductionofnon-recyclableproductsthatharmthebiosphere.>Reducetheuseofplasticsinbuildingmaterials,wherefeasible.>Usebio-basedandbio-degradableplasticsproducedwithrenewableenergy.>Designfordisassemblyandre-use.>Standardizethechemicalcompositionsofpolymersforeaseofrecycling.>Increasetransparencyand/orstandardizechemicalcompositions.>Tracematerialusagetokeeptrackofavailablestock.>Increasemateriallifewithlow-carbonmaintenancepractices.>Investinmuchgreatercollection,sorting,andmechanicalrecyclingtoavoidproductionofnewplastic,complimentedbyimprovedchemicalrecycling.>Avoidnewdemandbyextendinglifetimesofbuildingsandcomponents.>Incentivizeandsupportlocallyproducedandrecycledglasssources.>Improveresearchonefficientmeltingtechniquestoavoidemissions.>Shiftglassproductiontobestavailabletechnologiesandrecycling.>Electrifyproduction,construction,andtransportwithrenewableenergy.>Useprocessintensificationandwasteheatrecovery.>Designstandardcomponentsandfaçadesurfacingforrecycling,re-use.>Designglassfaçadesthatminimizeheatabsorptionandreflectionandinsteadcapturesolarenergyforheating,cooling,waterandlighting.64BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREMasonryTimberandWoodBambooBiomassLivingMaterialsTRANSITIONALRENEWABLEMATERIALS>Regulatequarryclosuretorestorenaturallandscapes.>Usestructuralandfacingbricktoincreaselongevityandreducemaintenance.>Replacehigh-carboncementbinderswithlower-carbonalternativebinders.>Usecement/mortaralternatives,suchasflyashwasteandsewagesludgeash.>Designmasonryunitsfordisassemblyandre-use.>Incentivizelocal,low-carbonearthmasonrymaking.>Educatedesignprofessionalsinmethodstoenhancethelongevityofnon-stabilizedearthmasonry.>Incentivizerenovationoverdemolition.>Incentivizeforestlandsownerstodevelopsustainablemanagementandbiodiversity.>Improvethedesignofforestbyproducts,toimprovecircularityintimber.>Improvecollectionratesof“clear-cuts”fromloggingpracticesandoff-cutsfromwoodmanufacturingforwoodproducts.>Improvewoodmanufacturingtocapturelossfromtimberprocessing.>Promoteandincentivizetheuseandre-useofstructuralmasstimber.>Trainandupskillconstructionactorsindesign-for-disassemblywood.>Updatebuildingcodestomandatereliablycertifiedproducts.>Incentivizetheresearchanddevelopmentofnon-toxicgluesandbinders.>Increasepolicysupportforcommercialenterprisestransitioningtohighlyproductiveandsustainablebambooforestmanagement.>Improvebambooplantpropagationmethods.>Transitionbamboomanufacturingtoon-siterenewableenergy.>Promotematerialefficiencybydevelopingstructuralstandardsfordifferentregionalspeciesandcirculardesign.>Incentivizetheuseofnon-toxicchemicalsandglues.>Integrateand/oradaptbamboostandardsforlocalbuildingcodes.>Educatearchitecture,engineeringandconstructionprofessionals.>Integrateintersectoralbiodiversebiomasssupplychainmanagement.>Incentivizeandinvestintechnologiesandbioadhesives.>Redirectbiomasstowardshigher-valueend-of-useproducts.>Createfinancialincentivesforthecaptureofbiomassbuildingmaterials.>Educateandtrainbuiltenvironmentprofessionalsindesign.>Educatestakeholdersoneffectivemaintenanceofproducts.>Educatefinanceandinsurancecompaniestoincentivizeadoption.>Implementmarketingandeducationprogrammes.>Trainandupskillmaterialrecoverymanagementtoimprovere-userates.>Understandnativeecologicalsystemsandcontextbeforeintroducingnewlivingbiomassmaterial;Usenativespeciesandorganicfertilizer.>Adaptdistrict-scalecarbonincentivesforimpactstourbanheatislandandstormwaterinfrastructure.>Designwithlow-carbonmaterialsubstructures,growingmedia,passivesolarenergy,andharvestedrainwaterforirrigation.>Provideavenuesforcircularcompostandwasteby-productrecovery.>Minimizematerialusethroughtheoptimizationofstructures.>Minimizeweightofmaterialsbyusinglesswaterandsoil.65BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE6Toolsareemergingthatenableverificationandtrackingofmaterial,energyandinformationflowsacrossthebuildinglifecycle.TOOLSforAssessingCarbonImpactAcrosstheBuildingLifeCycle666.1MeasurementandDataareImproving,butTransparencyandVerificationareNeededTheuseofreadilyavailabletoolstomanage,visualizeandcommunicatethedatabehinddecisionscanbegame-changing.Comingtogethertoconstructsustainablebuildingsandcitiesishardwork.Shiftingtheprocesstowardsbio-basedandcircularrenewablematerialsmakesitevenmorechallenging.Theuseofreadilyavailabletoolstomanage,visualiseandcommunicatethedatabehinddecisionscanbegame-changing.Informalconstruction,wheresupplychainsforbuildingmaterialsandsystemsarehighlycomplex,computationaltoolsanddatavisualisationframeworksarekeyinhelpingdecision-makerscomparetheprosandconsofdifferentmaterialsintermsoftheirembodied,operationalandend-of-useemissions.However,hugediscrepanciesinaccesstosuchtoolsexistacrosstheformaltoinformalconstructionsectors.Tocomplywithincreasinglyambitiousemissionreductiongoalsandpledges,stakeholdersacrossthebuiltenviron-mentsectoraretakingresponsibilityforawiderscopeofinformation,inordertodelivermaterialsandsystemsthathavepredictableandverifiableenvironmentalperformance.Datamanagementandvisualisationtoolsareemergingthatoffer“at-a-glance”scenariostosupportdecision-makinginrealtime.However,aswithenvironmentalassessmentsandcertificationsacrossallsectors,theverifiabilityofdataremainsahugechallenge.Thereisasignificantrangeinthequalityandquantityoftransparentdata,regulatoryprocedures,andcertificationprocessesacrossallmaterialsectors,eventhemostdevelopedones,resultinginuncer-taintyonthepartofmaterialspecifiers.Thetransparentmeasurementandqualityofdataontheenvironmentalimpactsofconstructionmaterialscontinuestoimprove.Accessibleandtransparenttoolsareemer-gingthatinvolvethird-partyverificationandtrackingofglobalmaterial,energyandinformationflowsacrossthebuildinglifecycle,providingthepolicyenablersformarkettransformation.However,considerablechallengesremainincomparingtheenvironmentalimpactsofmaterialsandsystemsthroughtheuseofthird-partycertifications,duetovariabilityindataquality,methods,functionalequivalencies,etc.(seeFigure6.1).©ShopArchitects6.1MunicipalbuildingenergycodesneedtotransitiontoincludeembodiedenergyVariousrequirementsandchallengesarenecessaryforsuchatransition.AdaptedfromAmericanCouncilforanEnergy-EfficientEconomy2021.REGULATIONANDMARKETDEMANDBuildingspeciﬁcations,standardsandcodescanbeeffectivepolicyapproachestoacceleratetheshifttolow-emodied-carbonbuildingsbyinﬂuencinggeneralpracticeinthebuildingindustryandincreasingmarketdemand.BENCHMARKNoconsensusexistsonhowtobenchmarkorbaselinethelife-cycleembodiedcarbonofabuilding.Guidelinesareneededtoevaluatethetrade-offsbetweenembodiedandoperationalcarbon.DATAExistingdataandpoliciesareatthemateriallevelandfocusonmanufacturingprocesses.Moredataareneededonthedurabilityandresilienceofmaterialsanditsimpactonembodiedcarbon.CAPACITYManufacturers,constructioncompaniesandtradesneedtobuildtheircapacitytoparticipateindatacollectionandreporting.BUSINESSCASEBusinesscasesneedtobedevelopedformanufacturerstointegratebuildingdecarbonizationwithindustrialdecarbonization.Istheworldreadyforembodiedenergybuildingcodes?67BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURETable6.1TOOLSANDSTANDARDSUSEDTOASSESSLIFE-CYCLEEMISSIONSLife-CycleAssessmentLife-cycleassessmentreferstoasystematicanalysisandevaluationofthepotentialenviron-mentalimpactsofmaterialproductsorservicesduringtheirentirelifecycle,fromproductiontodistribution,operationandend-of-life(oruse)phases.In2006,theInternationalOrganisationforStandardisation(ISO)issuedtworevisedstandardsforlife-cycleassessment–ISO14040and14044–thatsetoutafour-stageassessmentprocess:1)goaldefinitionandscoping(ideallyinclu-dingalldirectandindirectsourcesofemissionsthroughoutthelifecycle),2)life-cycleinventory(collectingdataonallthesysteminflowsandoutflows),3)impactassessment(classifyingtheseflowsintoenvironmentalimpactcategoriesandcharacterisingthembytheirimpactpotential)and4)interpretation(ISO2006a;ISO2006b).GHGProtocolTheGreenhouseGas(GHG)Protocol,foundedin1997,aimstoestablishasetofclear,rigorousandconsistentaccountingrulestocalculatethe“carbonfootprint”ofproducts.Theinitiativeintroducedathree-foldcategorisationoflife-cyclegreenhousegasemissions:scope1(directemissionsfromownfacilitiesandvehicles),scope2(indirectemissionsfrompurchasedelectricityandfuels)andscope3(emissionsfromallotherupstreamanddownstreamactivities).Ofspecialinteresttothebuiltenvironmentsectoraresoftwaretoolsthathelpcalculatethegreenhousegasemissionsofspecificsub-sectorsandmaterials,includingaluminium,cement,ironandsteel,andwood.Importantly,theGHGProtocolalsoincludesseveralcomplementarystandardsforthecalculationandmanagementofemissionsatdifferentscales,fromproductstothecorporateleveltowholecities.EnvironmentalProductDeclarationsEnvironmentalproductdeclarationsareoneofthreetypesofenvironmentallabelsestablishedunderISO14020standardsforecologicallabelling,designedtohelpbusinessesmeasureandcommunicatetheireffortstominimisetheirenvironmentalimpact(ISO2006c;ISO2016;ISO2018;ISO2022b).Ofthethreelabelcategories–certifiedeco-labels,productself-declarationsandenvironmentalproductdeclarations–onlythelattermandatestheuseoflife-cycleassessmenttoquantitativelyestimatelife-cycleimpacts,includinggreenhousegasemissions.In2012,theEuropeanCommitteeforStandardisation(CEN)publishedstandardEN15804toregulatehowlife-cycleassessmentsareappliedtoenvironmentalproductdeclarationsintheconstructionsector(CEN2019).However,concernsremainamongstakeholdersregardingthelimitedtransparencyandaccesstodevelopmentprocessesforenvironmentalproductdeclarations(GelowitzandMcArthur2016).ProductEnvironmentalFootprint(PEF)andOrganizationEnvironmentalFootprint(OEF)Since2012,theEuropeanCommissionhasbeendevelopinganambitiousschemeaimedatprovi-dingdetailedguidanceforcalculatingthe“environmentalfootprint”ofaproductandorganisation(EuropeanCommissionJointResearchCentren.d.).Whilebasedonlife-cycleassessment,theseeffortsaimtoimproveconsistencyandcomparabilitybymandatingspecificchoicesintermsofsystemboundary,allocationprocedures,impactassessmentmethods,etc.Onenotableinnova-tionistheuseofa“circularfootprintformula”toenabletheconsistentcalculationofend-of-liferecyclingcreditsacrossalllife-cycleassessmentsthatarecompliantwiththePEF.DevelopmentofthePEFmethodologyisstillinprogress,butithasalreadyresultedinatleastonemandatorystandard:the2019revisionofEN16804+A2fortheEuropeanconstructionsector(CEN2019)withamorerigorousaccountingofbiogeniccarbonflows.Adetaileddiscussionofthemethodologicalimplicationsofthisformulaisbeyondthescopeofthisreport,butitisessentiallyacaseofestablishinganagreed-uponcompromiseratherthancorrectingorimprovinguponthepreviouslyexistingalternativemethodologicaloptions.68BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREThechallengeacrossallglobalsectors,frominformaltoformalconstruction,istogettherightdatatotherightstakeholdersattheconsequentialstagesofdeci-sion-making.Eveninthemostenhancedbuiltenvironmentprocesses,certificationssuchasfulllife-cycleassessmentaretoocumbersometoconductatthecriticalinitialstagesofplanning.Often,materialchoicesandsystemsaresetinmotionduetosocio-economicorculturalpressuresandaredifficulttoshiftonceamulti-stakeholderprocessisestabli-shed.6.2ExistingToolsforAssessingCarbonImpactDecision-makersneedeasieraccesstotherightdatatoassessthecarbonimpactsoftheirmaterialchoices.Fordecision-makerstoadoptandapplywholelife-cyclethinkingandmakeoptimaldecisionsaboutdecarbonisation,theymusthaveaccesstotherightdatatoassessthecarbonimpactsoftheirmaterialchoices.Rigorousestimationofthe“carbonimpact”ofbuildingmaterialsacrossthebuildinglifecycleisnotaneasyortrivialtask,andinthepastsignificantexpertiseandtimewererequiredtomakeproperlife-cycleassessments(Takanoetal.2014).Currenteffortsareimprovingtheaccessibilityofthistaskthroughtheuseof“ataglance”tools.Analystsnowhavekeytoolstodrawfrom,developedduringthreedecadesofmethodolo-gicalrefinement,aswellasaseriesofdetailedandpragmaticsector-specificstandardsandguidelines.Thesetoolsattempttosolvetheproblemofproducingconsistentresultsthatcanbemeaningfullycomparedacrossstudies.However,furtherdevelopmentisrequiredtoaddressvariabilityindataprovenanceandreliability.Table6.1providesasummaryofsomeofthemostcommontoolsforassessinglife-cycleemissions.6.3RecommendationsforFutureCarbonAssessmentToolsEmergingtoolscanprovidenon-expertssuchasdesignersanddeveloperswithsnapshotsondataassociatedwithdiffe-rentdecisions;however,theyarestillatanearlystageandrequiremoredevelopment.Thekeytosupportingproductiveuseofthesetoolsisforthemtoprovidemoretransparencyandthird-partyanalysisandqualificationstothedata.DisseminatingDataandLow-CarbonMethodsinSemi-formalandInformalConstructionAddingdataontheeffectsofmaterialsonopera-tionalenergycostscouldbeakeyincentivetowardsshiftingconsumerpatterns.Accesstocarbonassessmenttoolsisdeeplyunevenacrosssectorsandregions,necessitatingalternativewaystocommunicatethecarbonimpactsofmaterialchoicestomorestakeholders.Althoughmostoftheconstructionboomindevelopingcountriesistakingplacewithouttheregulationofbuildingenergycodes,inaworldofsmartphones,manyinhabitantsacrossthespectrumofhousingtypes(formal,semi-formal,informal)arekeepingacloseeyeontheirenergyandwaterbills.Therefore,addingdatadetailingtheeffectsofmaterialsonoperationalenergycostssuchasheating,coolingandair-conditioningcouldbeakeyincentivetowardsshiftingconsumerpatterns,asbuildingoccupantsbegintounderstandhowtolowertheirenergybillsbysimplychoosingtherightroofingorcladdingmaterials.Forexample,conventionalbuildingmaterials–includingtheconcreteandasphaltoftenusedinroofing–absorbsolarradiationandemitheat,causingtemperaturestoincreaseandcoolingloadstosoar(Doulos,SantamourisandLivada2004;PradoandFereira2005;BozdoganSertetal.2021;Stacheetal.2022).Asinformalhousingrapidlyincreasesindensity,withdo-it-yourselfadditionsandupgrades,addingsimpledatatoutilitybillssupportsbuildingoccupantstomakedecisionsonadditionsandrenovationsusinglow-costbio-basedmaterialsthatlowertheirenergybillswhileimpro-vingthermalcomfort.CreatingDataandKnowledge-SharingNetworksAmongStakeholdersFuturetoolsneedtobeinteroperableandtocommu-nicateimpactsacrossthelifecycle.Perhapsthebiggestimpedimentfacingbuildingprofessio-nalswhodohavefullaccesstothelatestsoftwareisthattherearesomanydifferenttoolsavailable,andexpertsneedtobespeakingtoeachother(AlyEtmanetal.2016;AlyEtman,KeenaandDyson2017;Keena2017;KeenaandDyson2017;Keena,AlyEtmanandDyson2020).Thecompart-mentalisationandlackofcommunicationamongbuildingprofessionalsineachsectorresultsinsub-optimalmaterialdesignsthatcontributetoenvironmentalimpactsacrossthelifecycle(U.S.DepartmentofEnergy2008;DuPlessisandCole2011).AMcKinseyreportreinforcesthestagnantproductivitynumbersintheconstructionsectorandpredictsthat,facedwithsustainabilitydemands,thesectorwillneedtoreassessdigitalmethodstoreducewasteandabatecarbonemissions(Barbosa,WoetzelandMischke2017).Thereporthighlightstherolethat“bigdata”canplayinhelpingtoestablishcolla-borativenetworks,withefficientconstructionpracticesthattrackmaterial,energyandinformationflowsacrossthebuildinglifecycle.Intheconstructionphasealone,on-siteproductivitycouldincreaseby50percentbasedontheimplementationofdatatechniquesandaccuratedataflowsthroughstakeholdersystemsthatarebothbackward-looking(tracingbacktoproductionphase)andpredictive(modelling69BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREfutureusepatterns)(Barbosa,WoetzelandMischke2017).Bigdataoncarbon,energyandmaterialflowscanbeharnessedtoprovidestakeholderswithanat-a-glanceinteractivelookatthecausesandeffectsofmaterialchoicesanddecisions(Keena2017;KeenaandDyson2017;KeenaandDyson2020).Figure6.2showsanexampleofadashboardthatallowsstakeholderstoviewmultiplewindowstotrack,communicate,andassessmaterialflowsandenvironmentalimpactsacrossthelifecycle.Importantly,itharnessesarti-ficialintelligenceandbigdatatoenableuserstoquestiontheprovenanceandreliabilityofthedataandtocomparedifferentsources.Futureintelligentdataframeworkssuchasthiswillincreasethetransparencyandreliabilityofassessmenttoolsastheybecomemoreinteroperableandaccessibletoairqualitysensorsandsoftwarethathelptracktheemissionsofmaterialprocessesatdifferentphasesofthelifecycle,fromextractiontodemolition.Theywillalsoallowforbetterreal-timemonitoringofthelabourandenvironmentalconditionsofconstructionsites.InCanada,thenewDataHomebaseapplicationenablesstakeholderstoaccesstheestimatedenergyuse,carbonemissionsandaffordabilityindexesofresidentialbuildingsacrosscities(seeBox6.1).Visualisationframeworksthattraceamaterial’slineageandcharacteristics,aswellaspredictitsfutureimpactsonopera-tionalenergyandend-of-life,areespeciallycriticalforthedesignarchitectsandengineerswhohaveanoutsizedimpactonthedecision-makingprocessandtypicallyhaveverylittletimetojustifymaterialspecifications.Thisiscrucialtoensureconfidenceintheshifttowardslocallysourcedcircular,bio-based,andearth-basedmaterials,sincespeciesqualityandstructuralcharacteristicsvaryextensively.Hugestrideshavebeenmadeindevelopingaccessibledesignstandardsforbamboo(Harriesetal.2022),butframeworksforotherspeciesarelacking,withguidelinesalmostnon-existentforforestdetritusandagriculturalby-products.AssessmentToolsNeedtoConsidertheFullEcosystemicImpactsofBio-basedMaterialsItiscriticalthatfuturetoolsassessthelocalimpactsonregionalecosystemsfordifferentpracticesofextractingmaterials.Inscalinguptheglobalshifttowardsbio-basedmaterials,itiscriticalthatfuturetoolsassessthelocalimpactsonregionalecosystemsfordifferentpracticesofextractingmaterials,especiallyprimarytimberandbamboo.Life-cycleassess-mentsforbio-basedconstructionmaterialshaverarelyconsideredtheimpactsoflanduseandland-usechanges(Hoxhaetal.2020).Besidescarbonandclimatechange,landuseforbiomasssupplyalsoimpactsbiodiversityandecosystemservices(Verkerketal.2014;Gaudreaultetal.Likemanycountriesworldwide,Canadaisfacingahousingcrisis.Oneapproachtotacklinghousingsupplyisthroughthecirculareconomy,bykeepingmaterialsandbuildingsinuseforaslongaspossibletoreducewasteandpromotesustaina-bility,andbyre-usingbuildingmaterialsratherthanturningthemintowaste.However,effectivecirculareconomydecision-makingrequiresrobustdataonbuildings,andinmostcasesthesedataarewidelyscatteredandlackstandardisation.Toovercomethisbarrier,aninterdisciplinaryteamledbyresearchersatMcGillUniversityhasdeveloped“housingpassports,”orstandardiseddigitaldescriptionsofresidentialbuildingcharacteristics.Eachhousingpassportrepresentsdifferentresidentialtypologiesbasedonanalysisoftheexistingbuildingstock.Throughanewweb-based,datavisualisationapplicationcalledDataHomebase,housingpassportinformationisorganised,linkedandvisualisedinamannerthatmakesiteasilyaccessibletoawidevarietyofhousingstakeholders,fromthebuildingsectortofinanceandpolicymaking.Forexample,housingpassportscanhelpbankscompletepropertyassess-mentsandhelpcitiesmanagegovernmenthousingassets.DataHomebaseintegratesandannotatesdata,displayingcalculationsofestimatedenergyuse,carbonemissionsandaffor-dabilityindexesofresidentialbuildingsacrossCanadiancities.Itdoesthisatmultiplescales:thecityscale,theneighbourhoodscaleandthebuildingmaterialsscale.Byprovidingacompre-hensivedisplayofabuilding’sdegreeofcircularityacrossthesescales,theappallowsstakeholderstodetectwhichbuildingsatthecityandneighbourhoodlevel,andwhataspectsofanindividualbuilding,areprimedforimprovement,fromretrofittomaterialrecovery.Stakeholderscanusethesedataasaresourceforimplementingnewcircularbuildingdesignstrategiestowardsmitigatinghousing-relatedgreenhousegasemissions.BOX6.1DATAHOMEBASE:AWEBAPPLICATIONVISUALISINGCANADA’SHOUSINGCHARACTERISTICSTOFOSTERACIRCULARECONOMYSource:KeenaandFriedman2022.70BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE2016;Ferrarinietal.2017).Giventhehugeregionalvariationsofecosystems,suitablebiomasssourcesandproductionscalesneedtobeassessedandidentifiedattheregionalleveltoensurethattheuseofbiomasssupportshealthyecosystems.Currentlife-cycleassessmentmethodscansupportholisticassessmentofsomeenvironmentalimpactsbutnotall.Forexample,assessingtheimpactsonbiodiversityandecosystemserviceswillneedothercomplementarytoolsanddataforregionalassessment(Winteretal.2017;VanderWildeandNewell2021).Differentlife-cycleassessmentmethods(forexample,attributionalandconsequentiallife-cycleassessments)andcarbonaccountingframeworksexist.Thesuitabilityandpracticalityofthesemethodstosupportpolicymakingforbio-basedbuildingmaterialswillneedtobeassessed.Attheglobalscale,thereisanurgentneedtosupportthedevelopmentofpredictivemodelstoanticipatetheimpactsonglobalecosystemsofscalingupbio-basedmaterialprocesses.TheuseofbiomassaffectsdiverseecosystemsthatremoveCO2fromtheatmosphere,whichshouldbeconsideredwhenassessingtheimpactsofbio-basedmate-rials.Forexample,onestudylinkedalife-cycleassessmentmodelofcross-laminatedtimberwithaforestdynamicsimulationforapineforestinthesoutheasternUnitedStatestounderstandthecarbonfluxesassociatedwiththelifecycleofbothcross-laminatedtimberandforestlandssupplyingwoodacross100years(Lanetal.2020).Furtherpredictivemodelsandassessmentstudiesareurgentlyneededforallregions,especiallyinemergingecono-mies,tosetthepolicyforsustainablemanagementofbothforest-basedandagricultural-basedbiomaterialstocks.6.4ToolsforGreenhouseGasAssessmentAreNeededforDistrict-ScalePlanningUrbanplanningoftenignoresemissionsrelatedtositepreparation,whichcanaccountfor12%ofaneighbourhood’slife-cycleemissions.Greenhousegasassessmentsatthelevelofindividualbuildingsareanimportantstepandarebecomingcommoninmanypartsoftheworld.However,broaderperspectivesarealsoneeded.Urbanplanningoftencompletelyignoresemissionsrelatedtothepreparationofthebuildingsite(e.g.,earthmovingandsoilstabilisation),infrastructureconstruc-tionandmaintenance,traffic,andsoilandvegetationcarbonsinks.Suchomissionscanleadtoskewedperspectivesonprioritiesinlow-carbonurbandevelopment.6.2TheClark’sCrow“ataglance”datatoolThetoolshowstheenvironmentalandsocio-economicimpactsofmaterialchoicesacrosstheentirelifecycle.Source:Keena,AlyEtmanandDyson2020.71BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREBOX6.2FINLAND’S“AT-A-GLANCE”AVATOOLFORGREENHOUSEGASASSESSMENTATTHENEIGHBOURHOODLEVELHelsinki,Finlandisusinganeighbourhood-levelgreenhousegasassessmenttoolcalledAVA,whichcanbeappliedtodetailedplanscoveringonetofivebuildings,orurbanblocksofapartmentsand/orofficebuildings.AVAwasdevelopedtobeappliedquicklyandpracticallytotypicalurbanplans,sothataplannercanuseitwithoutexpertunderstandingofgreenhousegasassessments.Despitethetool’ssimplicity,itsresultshavebeenshowntogenerallyalignwithothermethods(Tevajärvi2022).KeygoalsinAVA’sdevelopmentweretocapturethemainsourcesofemissionsinbuildingsandinfrastructureandtofocusonissuesthaturbanplannerscaninfluence,suchasidealmaterialrequirementsforstructuresandfoundations,thechoiceofconcreteortimberforthestructuralframe,thelevelofenergyefficiency,andacapontheoverallcarbonfootprint.Thisforeshadowsanupcominglawthatwillmakecarbonfootprintcalculationsrequiredforallnewbuildings(Kuittinen,IlomäkiandKoskela2021).ThespeedandeaseofuseofAVAallowdesignerstocomparetheenvironmentalimpactsofdifferentoptionsforasite.Importantly,thetoolcanbeappliedtolargerandmorecomplexplans,althoughusersneedtobeawareofthetool’slimitationsasaballparkassessmenttool;onmorecomplexinfrastructureneeds,assessmentswillneedtobesupplementedbymoreexpertanalysis.Figure6.2showsresultsfromAVAassessmentof19differentdetailedplansinHelsinki,reflectingadiversityofbuiltareasizesandbuildinguses.InlinewithpreviousFinnishstudies(Puurunenetal.2021),theresultsindicatethatthreemainactivitiesdominateemissions:buildingconstruction,energyuseandtransport.Inmostcases,theconstructionandmaintenanceofbuildingsisbyfarthelargestcategoryofemissions.Thisshowsaclearshiftfromolderstudies,whichtendtoshowthedominanceofoperationalenergyinemissions.Thecontributionofbuildingsandconstructiontoemissionsislikelytogrow,asscenariosindicatethatbothenergyproductionandtransportcanbedecarbonisedrelativelyswiftlybasedonHelsinki’stargetsandcurrentactions.TheresultsinFigure6.3arerevealing.Forexample,theimpactofatimberframeisshownincase18,whichhasthelowestemissionsfrombuildingconstruction.Case4islocatedinawoodedarea,whichleadstoanoticeableimpactresultingfromthelossofcarbonsinks.Incontrast,cases12,14and18showdevelopmentswheresoilandvegetationcarbonsinkswerestrengthenedduringtheassessmentperiod.6.3Greenhousegasemissionspertotalfloorareafor19detailedplansassessedinHelsinki(50-yearassessmentperiod)Theconstructionandmaintenanceofbuildingsisbyfarthelargestcategoryofemissions.Note:Theassesseddevelopmentsrepresentawidevarietyofbuildingusesandtotalfloorarea.Source:Puurunen2023.012345678910111213141516171819200-2004006008001000BuildingsandLotsSoilandVegetationCarbonSinksInfrastructureTransportSitePreparationEnergyGHGemissions(kgCO2e/m2)STORAGEEMISSIONS72BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURETheimportanceofaccountingforthesewider-areaemis-sionsisheightenedbytheinsightthatthesearetheveryfirstemissionsreleasedduringthelifecycleofanurbanproject.Forexample,studiesinFinlandhaveshownthatemissionsfromsitepreparationcanaccountforupto12percentofaneighbourhood’stotallife-cycleemissions(Puurunenetal.2021).Inparttoaddressthischallenge,thecityofHelsinkihasadoptedthenewlydevelopedAVAtooltoassessemis-sionsataneighbourhoodscale(seeBox6.2)Climatepledgesanddecarbonisationpathwaysthatignorescope3emissionsmustbeseenasinadequate.Increasingly,citiesareadoptingmunicipalgreenhousegasassessmentstoaccountforlocal-levelemissions.UndertheGlobalCovenantofMayorsforClimateandEnergy,morethan12,000membercitiesestimatetheirannualemissionsbasedontheGlobalProtocolforCommunity-ScaleGreenhouseGasInventories(GlobalCovenantofMayors2016).Typically,city-levelpathwaystodecarbonisationarebasedonlyonscope1emissions(emissionsproducedwithinthecitylimits)andscope2emissions(energy-relatedemissions)(Fongetal.2021),withassessmentsforbuildingsbasedonthestandardEN15643.Scope3emissions,whichincludeemissionsthatoccuroutsidethecityboundaryasaresultofactivitiestakingplacewithinthecity,havereceivedlessattention(Linton,ClarkeandTozer2022).Theseincludetheembodiedemissionsofbuildingmaterialsandotherproductsusedincitiesbutproducedelsewhere.Climatepledgesanddecarbonisationpathwaysthatignorescope3emissionsmustbeseenasinadequate.Consump-tion-basedaccountingofemissionsisanabsolutenecessityasonebasisforsolvingtheclimatecrisis.Forexample,arecentcomparisonofgreenhousegasassessmentsin10Europeancitiesfoundthat,inallcities,assessmentsofscope1and2emissionsrevealedsignificantreductionsinemissions(upto68percent)(Harrisetal.2020).However,assessmentsofscope3emissionsshowedthat,in8ofthe10cities,consumption-basedemissionswererising,byasmuchas35percent.Thishighlightstheimportantroleofmeasuringandtacklingembodiedemissions.6.5GlobalStandardsandLabelsforEmissionTransparencyCanGalvanizetheMarketIfallG7economiesimplementedpoliciesthatfavourlow-carbonmaterialsandproducts,globalemissionscouldbereduced5.5%.Itisessentialthatallofthedifferentmethodsforidentifyinganddeclaringmaterials-relatedgreenhousegasemissionsbebroughtintogloballyregulatedcompliancethroughtransparentlabelling.Thiswouldhelpcreatealevelplayingfieldacrossthesupplychainandlifecycle.Materialprodu-cers–particularlyinemergingeconomieswhereresourcesforcertificationarelimited–mustbesupportedtoenablefair,third-partyverificationofprocessesandequipment.Forpurchasersofmaterials,suchindependentverificationisneededbysupplier,assembly,installation,geographyandasset.Themostimpactfulwaytofacilitatemulti-stakeholdercooperationacrossglobalmaterialsupplychainsisto“closethecarbonloophole.”Thismeansthatdevelopedeconomiesthatarenownetimportersofrawmaterials–andthathavecontributedthevastmajorityofpastgreenhousegasemissions–shouldnotbepermittedtopurchasethosematerialsat“discounted”pricesfromemergingeconomies,whichareobligatedtomaintainlowpricesthroughlaxenvironmentalandlabourregulations.Globalcooperationisneededtocreateanewtradeparadigm.IfallG7economiesimplementedpoliciesthatfavouredlow-carbonmaterialsandproducts,whileensuringfairtradeandlabour,globalemissionscouldbereducedby5.5percent(1.8gigatonsofCO2)(IEA2021).Thiswouldalsocreateafarmoreequitablesystemfortrackingemissionsacrossthemateriallifecycle.Closingthecarbonloopholewouldprovidepathwaysforproducersinthedevelopingworldtogainaccesstonewmarkets,byshiftingemissionsoffthebalancesheetsofdevelopingeconomiesandplacingmoreaccountabilityonconsumersinhigh-in-comecountriesthatboaststrictenvironmentalregulationsathome.Furthermore,alevelplayingfieldisessentialforthecreationoftransparentandverifiableinternationallabellingandcertificationprotocols.Publiceducationandpolicyarecriticaltoensurethatconsumershaveabetterunderstan-dingofthesocialandenvironmentalcostsofcheapmate-rials,fromforcedlabourtothedegradationofecosystems,speciesloss,forestfires,waterandairpoisoning,etc.Thedemandforlow-carbonmaterialscanbebolsteredbymarket-basedmechanisms,financing,certificationsandregulationstolowerrisksandcreateafair,competitiveplayingfield.Bordercarbonadjustments,suchastheEuro-peanUnion-ledCarbonBorderAdjustmentMechanism,ortradeagreementsliketheU.S.proposalforaGlobalArrange-mentonSteelandAluminium,bothannouncedinDecember2022,areexamplesofpolicyinstrumentsthatintendtominimisetheriskofunfaircompetitionand“carbonleakage”incross-bordercarbonaccounting.However,ifthesemechanismsaretotrulysupportglobaldecarbonisation,thentheirdesignmustaccountfortherealitiesofproductionanddemandinemergingeconomies.Globalagreementsoncarbon-adjustedbuildingmaterialmarketsandfinancingshouldbuildcapacitiesfortranspa-rentlyidentifyingandverifyingcarboncompetitiveness,sothatmaterialscanbefairlycertified(Brenton2021).73BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURETable6.2EMERGINGMECHANISMSTOSUPPORTWHOLELIFE-CYCLEDECARBONISATIONOFBUILDINGMATERIALSPerformance-basedbuildingcodesTheemergenceoflow-costtrackinghasenabledgreateraccesstodemand-sidemetricsonenergyandwateruseinbuildings.Transitioningtoperformance-basedbuildingcodesthatdrawonthesemetricscouldtransformwell-establishedcodes.Itwouldalsolendacriticalopportunityforemergingeconomieslackingexistingbuildingenergycodestoleveragetheirongoingbuildingboomtoleapfrogoveroutdatedprescriptivebuildingcodes,whichwerelargelybasedon“bestpractice”examples,with“one-size-fits-all”guidelinesthatareillsuitedduetothevariabilityoflocalmicro-climatesandbuildingtraditions.Performance-basedbuildingcodeshaveagreaterchancetoconnecttoarangeofstakeholders,fromglobalarchitecture,engineeringandconstructioncompanies,toowner-buildersininformalsettings.Examples:EnergyPlus,ZeroTool,BuildingEnergyModelling,AutodeskEnergyAnalysis,SefairaBuildingPerformanceSoftware,PVCalculator,DSIREEfficiency/EnergyIncentivesDatabase,WUFI.CarbonfootprintassessmentsEmergingcarbonfootprintassessmentsconveymoretransparentlythepotentialwholelife-cycleimpactsofembodiedandoperationalcarbon,bothfortraditionalconstructionmaterialsandforprefabricatedsystemsandassemblies.Throughcriticalcomparisons,stakeholderscanconsiderandtrackthebeneficialimpactsacrossthelifecycleofcomputer-enhanceddesign,procurementandproductionmethods.Thesebenefitscanincludeincreasingtheefficiencyofmaterialsandstructures,reductionsinon-siteemissionsfromconstruction,andtheimprovedabilitywithinfactoriestodesignfordisassemblyandcircularreuse/recycling.However,anticipatingtheimpactofmaterialsonoperationalperformanceiscomplexandneedstoaccountforfactorssuchaslocalbioclimate,buildingtypologies,systemsintegration,andhumanbehaviourandoccupationpatterns.Allofthesecancausegreatvariabilityintheoperatingperformanceofabuildingmaterialanditssystem.Examples:EC3CarbonCalculator,Tally,WoodWorksCarbonCalculator,AthenaImpactEstimatorforBuildings,OpenLCA,GLADEmbodiedcarbonlabellingWidediscrepanciescurrentlyexistinthemethodsandqualityofthelabellingofembodiedcarboninbuildingmaterials.Supportisgrowingfortheestablishmentofaninternationalstandardscommitteetooverseefairnessinthislabelling.However,moredevelopmentisneededofmethodsthataddressthe“carbonloophole,”sothattheconsumersandspecifiersofmaterialsincoun-trieswithstrictpollutioncontrolscanshareaccountabilitywithproducersfromregionswithlaxcontrols.Unfortunately,theinabilityofmanyproducers(particularlysmallones)topayforthecertificationoftheirproductscanleadtothembeingfurtherdisadvantagedbycarbonbordertaxes–thusleadingtothefurtherlooseningoflocalregulationstoensurethatexportsremaincompetitivelypriced.Examples:EC3CarbonCalculator,CradletoCradlecertified,DeclareLivingFutureInstitute.Low-carbonpublicprocurementpracticesMunicipalandnationalgovernmentsaresettingpoliciesandaggressivetargetsthatlimittheirchoicestolow-carbonalternativeswhenselectingcontractors.Thisisresultingintheestablishmentofleadingindustryprecedentsforintegrateddecarbonisationacrossmultiplescalesofinfrastructureandbuildings.Example:SeeBox6.2onHelsinki,FinlandIndustrypledgesGloballeadersinthearchitecture,engineeringandconstructionindustryaredevelopingpledges,internalbenchmarksandnovelmethodstotrackthecarbonimpactsoftheiractivities.Despiterampantaccusationsofgreenwashing,withmanyrisksofdatamanipu-lation(especiallywhenself-reported),ratingagenciesandeffortssuchastheScienceBasedTargetsinitiativeworkwithbusinessestoagreetoascience-basedtargetthatlimitsabusiness’globalshareofgreenhousegasemissions,withindependentverification.However,firmcommitmentsneedtobesecured.Theclimatepledgesmadeatthe2021UnitedNationsClimateConferenceinGlasgowwerefollowedbylawsuitsforgreenwashinginadvertising;thus,manyfirmsarechoosingtoavoidscrutiny.Examples:GreenBuildingPrinciples:TheActionPlanforNet-ZeroCarbonBuildings,SustainableConstructionLeadersPeerNetwork,Contractor’sCommitmenttoSustainableBuildingPracticesModelsforcoordinationModelsforcoordinationacrosstheforestry,agricultureandconstructionindustriesareemergingforenhancedcooperationonlanduseandthesupplyofbio-basedbuildingmaterials.Theaimistodevelopsupplychainsandproductsderivedfromtheupcyclingofforestdetritusandagriculturalwasteby-productsintobuildingmaterials,whichwouldinturngreatlyreducecarbonemissionsfromforestfiresandcropburning.Example:BuildCarbonNeutralCalculatorCarbonoffsetsAsgovernments,industryplayersandothersstrivetomeetnetzeroemissiondeadlines,demandisgrowingforcarbonoffsetsandrenewableenergycredits.Thisissettingthestageforanescalatingcarbonoffseteconomy.However,theactualdecarbonisationofbuildingmaterialproductionprocessesmaybehamperedbytheabilityofindustriestomarketso-callednetzeroproductsthroughtheuseofcarbonoffsetsofvaryingquality.Greaterregulationisneededincertifyingdecarbonisationoftheactualprocessesofmaterialproduction.Example:SeeBox6.3onLendleaseAmericas74BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREBOX6.3NETZEROCONSTRUCTIONATLENDLEASEAMERICASTheglobalconstructioncompanyLendleaseAmericaswasabletoreachnetzeroemissionsforitsroughly$2billionconstructionoperationsduring2021and2022.Thecompanyusedlife-cycleanalysistoinformmultipleconcurrentdecarbonisationpathways.Tomaintainalignmentwithapathwaytokeepglobaltemperaturerisebelow1.5degreesCelsius,Lendleasehascommittedtoachievingcarbonneutralityinitsscope1andscope2emissionsby2025,andabsolutezerocarbonemissionsacrossscopes1,2and3by2040.Thecompanyachievedits2025goalsearlyforitsU.S.constructionbusiness,largelybyreducingitssignificantoperationalemissions.Duringfinancialyears2020and2021,Lendlease’sU.S.operationsreleasedatotalof15,799metrictonsofCO2-equivalentemissions.Ofthis,scope1emissionstotalled9,411tons,derivedfromtheuseoffuelsfortemporaryconstructionelectricalpowergenerationandfuelsusedinoperatingmajorplantandequipmentsuchasexcavatorsandtowercranes.Lendleaseusednaturalgasandotherfossilfuelstoprovideheatingduringconcreteplacementincolderwintermonths.Inaddition,thecompanyemittedindirectscope2emissionstotalling6,390tonsthroughtheuseofelectricityforsitelightingandothertemporaryuses.Lendleaseisimplementingthefollowingstrategiestoreducebothscope1andscope2emissions:>utilizingelectricplantandequipmentthroughexpeditingpermanentpowerutilityconnection>useofbiofuelsandrenewablediesel>leveragingbatterystoragesolutionstoreducegeneratorsizing>Elliminatingfossilfuelheatingofconcreteplacementoperationsduringwintermonths>leveragingon-siterenewablessuchassolarforsmall-scaleapplications>purchasingcarbonoffsetsandrenewableenergycredits.LendleasechoseseveralU.S.renewableenergyprojectstoprocurecarbonoffsetsforitsscope1emissions,andalsopurchasedhigh-qualityrenewableenergycreditsforitsscope2electricityuse.Throughthesemeasures,LendleaseAmericasConstructionhasbeenoperating“netzero”sinceJuly2020.Lendleasebelievesintheimportanceofsharingbestpracticesforreducingcarbonemissionsassociatedwithconstructionandcollaboratingwithpeerstorapidlydecarbonisethisindustry.Source:Lendlease2022.Developmentsininternationaltrademechanismsmaybeabletochangethegameincombatingglobalclimatechange.However,foremergingeconomiesthathavehistoricallycontributedverylittletoclimatechange,butwherethemajo-rityofmaterialproductionandconsumptionwilltakeplaceinthecomingdecades,itiscriticaltofacilitatethedevelop-mentofaconsistentandcomprehensiveaccountingsystemtoaccuratelymeasureemissionsallalongthelifecycleandvaluechain,sothatthesecountrieshaveafairchancetodemonstratetheircarboncompetitiveness(ColumbiaCenteronSustainableInvestment[CCSI],InternationalInstituteforEnvironmentandDevelopment[IIED]andInternationalInstituteforSustainableDevelopment[IISD]2021).Totrulycreatealevelplayingfieldtowardsglobaldecarbonisation,manyemergingeconomieshavetakenthepositionthattheyshouldreceivealargeportionoftheproceedsfrombordercarbonadjustments,tosupporttheminadoptinglow-carbonmethodsandcertifications.Table6.2providesanoverviewofsomeofthemechanisms,includingcarbonlabelling,thatareemergingtosupportwholelife-cycledecarbonisationofbuildingmaterialsinbothdevelopinganddevelopedcountries.Box6.3providesanexampleofhowonecompany,LendleaseAmericas,usedlife-cycleanalysistoinformmultipleconcurrentdecarboni-sationpathwaysonthepathtonetzero.6.6ChallengesandNextStepsExcellentanalyticaltools,frameworksandstudiesareemergingtohelpidentifykeyleversandpracticesfordecarbonisationinthebuildingsector.However,thesemustbesupportedbyappropriatepolicy,accesstoqualitydata,andtransparentauditsconductedbyqualifiedthird-partyreviewers.Inanefforttoincreasethetransparencyofmate-rials,theDesignforFreedomToolkit(GraceFarmsFounda-tion2022)highlightsdozensofrelevantcertifications,labelsandstandardsthatincludefairlabouraudits.Notably,intheinformalsector,stakeholderstypicallyhaveneithertheaccesstodatanorthemeanstoconductsuchanalyses.However,feedbackincludedinutilitybillsandothermechanismscancontinuetoaddlife-cycleinformationontheimpactofmaterialsonoperationalenergyexpendi-tures,includingdesigntipsformaterialretrofitstoreducecosts.Thisinformationcanthenbefedintodistrictandevenurbanmodelsshowingcomparisonsacrosshouseholdsandbuildingtypes.Thisreportoutlinesthemostadvancedmethodsindecar-bonisationanalysisandpracticesintheformalrealm,whilesuggestingpotentialpathwaysforcooperationandexchangebetweeninformalandformalconstructionpractices.75BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE7Decarbonizingbuildingswillnotbepossiblewithouttakingawholelifecycleapproachtotheirconstructionandensuringtherapiddecarbonisationofbuildingmaterials.POLICYRecommendationsforDecarbonisingMaterialsintheGlobalBuildingSector76DECARBONISINGBUILDINGSWILLNOTBEPOSSIBLEWITHOUTTAKINGAWHOLELIFECYCLEAPPROACHTOTHEIRCONSTRUCTIONANDENSURINGTHERAPIDDECARBONISATIONOFBUILDINGMATERIALS.Buildingmaterialchoicesmadeininfrastructurepolicy,urbanplanningandbuildingdesignrequirementshaveprofoundimpactsonGHGemissions.Theprecisesetofpoli-ciestooptimisebuildingmaterialdecarbonisationmustbeinformedbytheassessmentofthespecificcontext.Regu-lationisrequiredacrossallphasesofthebuildinglifecycle,fromextractionofmaterialsthroughend-of-useofbuildings,toensurethedevelopmentofaviable,circularsupplychainofsustainablematerialoptions.Effortstodecarbonisethematerialsupplychainaresynergisticwithmeasuresunder-takentoensurefairlabourandgenderequity.Thisrequiresradicalcollaborationandsimultaneouslysupportingmaterialproducers/manufacturersandconsumerssuchasarchi-tects,developers,communitiesandbuildingoccupants.Policymakerswillneedtoengageallactorsacrosstheentirevaluechainandconcurrentlyenabletheimplementationofthethreemaindecarbonisationprinciplesdiscussedinthisreport:>AVOIDmaterialoveruseandnewmaterialextractionbybuilding(with)less,activelyseekingwaysofreusingandrecyclingbuildingsandmaterials.>SHIFTtosustainablyproducedlowcarbonrenewablebuildingmaterialssuchasearthandbiobasedmaterialswheneverpossible.>IMPROVEmethodstodecarbonisecarbon-intensiveconventionalmaterialssuchasconcrete,steelandalumi-nium,andonlyusethemwhennecessary.Acrossregions,implementationmethodswillvaryaspatternsinmaterialflowscenariosdiffer.Inhighlydeve-lopedregions,incentivesneedtofocusontherenovationofexistingandageingbuildingstock,whereasindevelopingregionswithrapidruraltourbanmigration,thereisanoppor-tunitytoradicallyre-inventnewconstructiontechniquesandleapfrogoverpriormodernpracticesbydramaticallyimprovingconventionalmaterialproduction,reconnectingwithexisting,localclimate-specificbuildingknowledgeandvernaculartraditions,andshiftingtosustainablysourcedbiomaterialswhereverpossible.Annex3providesshortsummariesonhowcountriesthathaveverydifferentbuiltenvironmentcontexts–Canada,Finland,Ghana,Guatemala,India,PeruandSenegal–canpursuedecar-bonisationusingthe“Avoid-Shift-Improve”strategies.Todrivemarkettransformationandstakeholderaction,governmentsshouldtakeactionto:1.Setthevision,leadbyexampleandimprovemulti-levelgovernance2.Makecarbonvisiblethroughimproveddataaccessandquality3.Adaptnormsandstandardstoallowfortheuseofcircular,alternativeorlower-carbon,bio-basedbuildingmaterialsandconstructionpractices4.Acceleratetheindustrytransition5.Ensureajusttransition6.Strengtheninternationalactionandcollaborationforcollectiveimpacts7.1SettheVision,LeadbyExampleandImproveMultilevelGovernance7.1.1RallyingAllStakeholdersBehindtheWholeLifeCycleApproachSinceitiscriticalforactorsinthebuildingsandconstructionsectortoworktowardstheimplementationofawholelife-cycleapproachtobuildingsandconstruction,policymakersshouldstartbytakingstockofthecurrentsituationandpracticesinordertobringdiversestakeholdersofthebuil-dingsandconstructionvaluechainbehindacommonvisiontoovercomethefragmentationinthesector,andrampupboththelevelofactionandambitiontowardsdecarbonizingbuildingsalongtheirlifecycleandmakethemdurableandclimateresilient.Box7.1highlightsGlobalABCGlobalandRegionalRoadmapsasanexampleproductofstakeholderengagement.©Pixabay/Pexels77BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREKEYACTIONINSTITUTIONALISESTAKEHOLDERCOORDINATIONANDDEVELOPNATIONALANDSUB-NATIONALROADMAPSANDACTIONPLANSFORTHEDECARBONISATIONOFTHEBUILTENVIRONMENT>Initiateacountry-ledstakeholderengagementprocessthathelpstobringallactorsofthevaluechaintogethertoidentifyactionsandprioritiestotransformthebuildingsandconstructionsector(e.g.followingthemodelofGlobalABC’sRoadmapsforBuildingsandConstruction).>Establishandinstitutionaliseacoordinationmechanismtofacilitatecollaborationandsynergiesbetweenactors,facilitatecollaborativeactions/synergiesandensurethesearenotaffectedbyshort-termpoliticalcycles.7.1.2HarnessPublicProcurementtoSupportDecarbonisationofMaterialsThepublicsectorcanplayaleadingroleinenablingbuildingmaterialdecarbonisationthroughitsprocurementpowers.Publicprocurementexpenditures–governmentpurchasesofmaterials,productsandservices–compriseupto13percentofgrossdomesticproductinmembercountriesoftheOrganisationforEconomicCo-operationandDevelopment,withevenhighersharesindevelopingeconomies(Baron2016).TheimpactofpublicprocurementingeneratingmoresustainablegrowthisoutlinedinSustainableDevelopmentGoal12(Target12.7).Policygoalsfordecarbonisationmustbeformallylinkedtothepurchasingofmaterials,withadditionalbudgetsintheplanningphasesforrigorouswholelife-cycleassessmentsforpublicprojects,inordertoimprovethedataontheimpactofmaterialchoicesandserveasexamplesforeffectivesolutionsacrossspecificlocalclimatetypes.Inregionswherethevastmajorityofbuildershaveneitherthemeansnortheinclinationtoconductsuchanalyses,publicworksprojectsserveasespeciallycriticalexamplesfordemonstratingtheprinciplesof“Avoid,ShiftandImprove”asoutlinedinthisreport.Practicalstrategiesincludetenderswithlife-cyclecostinginvalue-for-moneyassessments,whichincludethecostofexternalitiessuchasCO2.Marketdialoguesandinternationalcollaborationcansupportbothmaterialprocurersandprodu-cersacrossthesupplychaininformulatinginnovativetenders,andencouragenewbusinessmodelsthatprovideservicestosupportreductionsinmaterialuseandenvironmentalimpacts(Baron2016).KEYACTIONLINKPUBLICPROCUREMENTWITHDECARBONISATIONPRACTICES>Formallylinkpolicygoalsfordecarbonisationtothepurchasingofmaterials.>Provideforadditionalbudgetsintheplanningphasesforrigorouslife-cycleassessmentsforpublicprojectsandpublishtheresultstoimprovethequalityandquantityofdataontheimpactofmaterialchoicesandtodemonstratesolutionsacrossclimatetypesandbuildingtraditions.>Issuetendersthatincludelife-cyclecostinginvalue-for-moneyassessments,whichincludethecostofexternalitiessuchasCO2.>Convenemarketdialoguesandinternationalcollaborationtosupportbothmaterialprocurersandproducersacrossthesupplychaininformulatinginnovativetenders.>Encouragenewbusinessmodelsthatsupportreductionsinmaterialuseandenvironmentalimpacts.7.1.3EmpowerCitiesandMunicipalitiesasDriversofChangeGovernmentsmustimprovemultilevelgovernanceframeworksandmechanismstobetterimplementandenforcebuildingsandconstructionregulationswhichsupportwholelifecycleapproachesandlowcarbonmaterialefficiencystrategies.TheGlobalABCGlobalandRegionalRoadmapsforBuildingsandConstructioninAfrica,AsiaandLatinAmericahelpsetpathwaystodecarbonisationofthebuildingsandconstruc-tionsectorby2050.Theseroadmapsarebeingcascadedtosub-regional,nationalandsub-nationallevelsleapingforwardtowardsimplementationinover30countries/jurisdictions.Theroadmapsaredevelopedthroughparticipativestakeholderengagementprocessandpresentacomprehensiveapproachtoemissionreductionsfromthebuiltenvironmentalongthefulllifecycle,withaspirationalshortandmediumtermandlonger-termtargetsgoals.SeeRoadmapsforBuildingsandConstructionGlobalABCBOX7.1GLOBALABCROADMAPSFORBUILDINGSANDCONSTRUCTION78BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURECitiesmustbeempoweredtoimplementandenforcedecarbo-nisationpoliciesincollaborationwithnationalandsub-nationalgovernmentinstitutionsaspartoftheirlocalactionplansforbuildingsandconstruction.Theyneedtopromotesustainableenergysolutionsandencouragepassivedesign,circularity,nature-basedandneighbourhoodlevelsolutions,incentivizingbuildingsandconstructionindustrystakeholdersaschangeagents.Aschampionsforimplementingandenforcingclimatepoliciesandtargets,citiesareuniquelyplacedtocatalysethistransitionthroughtheirjurisdictionoverlanduse,authorityoverhousingprogrammes,roleinimplementingnationalpoli-ciesandbuildingcodes,andtheirroleincoordinatingwithlocalutilitiesandstakeholders.Thepublicsectorisofteninthebestpositiontoimplementdecarbonisationplansatlocalordistrictscale.Itcanhavemaximumimpactfornewdevelopment,sincestrategiesforindividualbuildingscanbeintegratedinsynergywiththedesignofsustainable,electrifiedgridsforthemanagementofenergy,water,wasteandtransport.Policiesandambitioustargetsfromlocalandnationalgovernmentsestablishleadingprece-dentsforintegrateddecarbonisationacrossmultiplescalesofinfrastructureandbuildings(seeBox6.2onHelsinki).Thisisonlypossibleifmaterialchoicesandurbanplanningavoiddrivingupcoolingdemandsthroughthecreationofurbanheatislandsandinsteadlowerstheoveralloperationalcarbonofcitiesbymandatingbiomassmaterialsandothercoolsurfaces.KEYACTIONIMPLEMENTCOORDINATEDDECARBONISATIONACTIONSATTHELOCALORDISTRICTSCALE>Implementlocalorneighbourhood-levelbuildingdecar-bonisationplansforcoordinatedactionbyestablishinggridintegrationschemesandlocalmaterialbanksforandrenovatingbuildingenvelopesornewconstructionswithlowcarboncircularorbiobasedmaterials.>Createincentivesatthelocalleveltoovercomeinitialandongoingmaintenancecosts.KEYACTIONMANDATETHEUSEOFLIVINGSYSTEMSANDBIOMASSTOPROTECTURBANCLIMATES>Includeminimumrequirementsinbuildingcodesforvegetatedsurfacesforurban-scalebuildings.>Provideincentivesforsmallerbuildingstoincorporatelocallyappropriateplantspeciesintoroofsandfaçades.7.2MakeCarbonVisibleThroughImprovedDataAccessandQuality7.2.1EnvironmentalLabellingStandardsandCertificationsThereisaneedforinternationalenvironmentallabellingstandardswithestablishedstandardprotocolsandlicensedthird-partyverificationforbuildingmaterialsaswellasbuil-dings.Toensurethevalidityoftheclaimsandtofacilitatefaircompetitionamongproducers,transparent,scientificallysoundmethodsanddocumentationarerequired.Currently,theInternationalOrganisationforStandardisation(ISO)specifiestheprotocolsforallself-declaredenvironmentalclaimsofmaterials,includingwhatstatements,termsand/orgraphicsarepermitted,andprovidesqualificationsandveri-ficationmethodology.However,regulationandenforcementtoensurecomplianceisstillseverelylackinginmostsectors,leadingtopotentiallynegativemarketeffects.Risingpublicinterestinenvironmentallysoundconstructionpracticeshasledtoafloodofself-declaredenvironmentalclaimsfrommaterialproducers,withlimitedtraceability–generatingscepticismandbacklash.Forcertificationtofacilitateatransitiontolow-carbonmaterialsinafairandequitablemanner,moredevelopmentisrequiredformethodsthataddressanother“carbonloophole,”sothattheconsumersandspecifiersofmaterialsincountrieswithstrictpollutioncontrolssharetheonusforthedecarboni-sationofthematerialstheyconsumewithproducersfromregionswithnoorminimalcontrols.KEYACTIONPROMOTECLEARANDCONSISTENTSTANDARDSFORCARBONLABELLING>Attheveryleast,allmaterialproductsshouldbecertifiedwithinternationalstandardssuchastheGHGProtocolProductStandard,ISO14067orPAS2050.However,therearestillsomanybarrierstogettingthesestandardcertifications,andfarmoresupportneedstobegiventosmallerenterprises,particularlyindevelopingregionsifthereistobearealisticexpectationoffairnessacrosssuppliers.>Supportforenforcingfairregulationisabsolutelycritical,iflabelsaretobetakenseriouslyinmanymarketsthatcurrentlyeschewthecostofcertification.>Needtoaddressthebacklashfromrampantperceptionsof‘greenwashing’inthemarketplace.79BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE7.2.2LifecycleAnalysisofBuildingMaterialsinConstructionandRenovationProjectsCommonmetricsandconsistentassessmentprocessesallowdecision-makerstoaccuratelyweighthetrade-offsinprioritisingthedifferentdecarbonisationpathways,inordertoaccuratelyinformeffortstosetstandardsandtradepolicy.Oftenjustmakingthisdatavisible(e.g.throughlabels)canhaveeffectsonwhichpathwaysarechosenandpursued.However,furtherdevelopment,internationalcooperationandcoordinationisurgentlyrequiredinordertoensurefairnesswithaccurateandtransparentdata.Manytoolsareonthemarketthatallowacalculationofthecarbonfootprintofbuildingmaterialswhichisagreatfirststep,howevertheaccuracyandrelevanceofthedataneedssubstantialdeve-lopmentinregulatoryandverificationprocedures.Thedataavailability,especiallyindevelopingcountrycontextsneedstobevastlyimproved.Nevertheless,therearenowmanytools,suchastheEDGEtool,thatallowforanassessmentofalternativesalready,andthesemethodsneedtobeencou-ragedinordertospurfurtherdevelopment.Goingforward,moresophisticatedtoolscanbefurtherdevelopedtocapturethebeneficialimpactsofcompu-ter-aidedproductionmethods–fromefficienciesinmaterialsandstructurestoreductionsinon-siteemissions–andtheimprovedabilityofcomputer-aided,factory-basedproductiontoreducematerialwasteandsupportdesignfordisassemblyandcircularre-use.Thiscouldalsoincludethevalueandrequirementsofnon-humanlivingsystems.Thus,thevaluesinwholelife-cycleassessmentsneedtoexpandtoincludetheworkofthegeo-biosphere,becauseinsomecasesithastakenmillionsorevenbillionsofyearsfortheEarthtoformcertainrawmaterials–suchastheironorerequiredtomakesteel–thatarethereforeirreplaceable,butevenseeminglyabundantbio-orearth-basedmaterialshavehighlyvariableimpactsdependingontheirorigin(KeenaandDyson2017).KEYACTIONPROMOTEEVIDENCE-BASEDMATERIALSELECTION>Mandatetheassessmentofthecarbonimpactofbuildingmaterials(LCA)inconstructionandrenovationprojects.KEYACTIONINCREASETHEAVAILABILITYOFHIGH-QUALITYANDIMPROVEDMETHODOLOGICALDEVELOPMENT>Fundresearchtodeterminebestpracticesforlife-cycleanalysisofecosystemimpacts,aswellasresearchandmethodologicaldevelopmentforwholelife-cycleassessmentsthatincludethegeo-biosphere.7.2.3ImproveAccesstoDataKnowledgeabouttheembodiedcarboncontentofthecurrentbuildingstockisneededforcalculatingemissionbaselinesandsettingmitigationtargets,andformonitoring,reportingandverification(MRV).KEYACTIONIMPROVEACCESSTOTRACEABLE,TRANSPARENT,RELIABLEANDVERIFIABLEDATA>Purchase,provideorsubsidisedataneededforassessmentsforkeystakeholderssuchasdevelopersincontextswherethesedataarecost-prohibitive.>Dramaticallyincreasethesupportforongoingtooldevelopmentanduseforstakeholdersacrossthesupplychaintobeabletomakerapiddesignandprocurementdecisionsandbeabletoverifytheprovenanceofmaterialsinrealtime.>Encouragedigitalisationandthedevelopmentofbuildingpassportstoassistinstandardisingdataandmakingthemtraceable,transparent,andverifiable.>Fundresearchtofurtherdevelopdatabanksthatcansupportfaircertificationandlabellingofmaterialsandbuildings.7.3AdaptNormsandStandardstoAllowforTheUseofAlternativeorLower-CarbonBuildingMaterialsandConstructionPractices7.3.1Introduce/StrengthenBuildingCodestoAddressEmbodiedCarbonMuchattentionhasbeenfocusedonreducingthecarbonimpactsofbuildingmaterialsinthecontextofformal,regu-latedpractices.However,mostglobalbuildingsectorshaveahighshareofinformalconstruction,withmorethan60percentofcountrieslackingmandatorybuildingenergycodes;assuch,morethan5billionsquaremetreshavebeenbuiltwithoutregulatedperformancerequirements(UNEP2022).Introducingandmandatingperformance-basedbuildingcodesthataddresstheperformanceofthebuildingenve-lopeandclimateimpactofbuildingmaterialsisessential.Ifenforced,buildingenergycodescanbethemosteffectivepolicyinstrumentforinfluencingenergyuseinbothnewconstructionandretrofits(IEA2018b).Emergingeconomiesthatlackexistingcodeshaveanopportunitytoavoidtherestrictionsofprescriptivebuildingcodesfromthefirstwaveof“environmental”buildingstandards,whichwere80BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURElargelybasedon“bestpractices”andwerenotalwaysadap-tabletolocalconditionsandpractices.KEYACTIONADOPTPERFORMANCE-BASEDBUILDINGCODES>Adopt(orstrengthen)buildingcodesthatencourageormandateevidence-basedandmaterialperfor-mance-basedrequirementsindesign.7.3.2EnforcePerformance-BasedBuildingCodesWiththegrowingadoptionoflow-costdigitisedtrackingmethods,aswellasaccesstodemand-sidemetricssuchasenergyandwateruse,performance-basedbuildingcodeshaveagreaterchancetoconnecttoarangeofstakeholdersacrosssectors,fromglobalarchitecture,engineeringandconstructioncompaniestooccupant/buildersininformalsettings.However,severalkeyimpedimentsneedtobeaddressedforwidespreadinclusionofembodiedcarboninbuildingcodes.KEYACTIONENFORCEPERFORMANCE-BASEDBUILDINGCODESTHATINCLUDETHEENVIRONMENTALPERFORMANCEOFMATERIALS>Mandatethetransitionfromnon-renewablematerialstolow-carbonbio-basedrenewables,hybrid,andrecycledmaterials,whereverpossible.>Buildsystemstocollectdataonoperationalenergycostsandtocreateinteractiveplatformsforuserstotracktheenergycostsofdifferentmaterialdecisions.7.4AcceleratetheIndustryTransition7.4.1RapidlyDecarboniseConventionalNon-RenewableMaterialsCement,steelandaluminiumarethethreelargestsourcesofembodiedcarboninthebuildingsector.Oneofthelowesthangingfruitsistofacilitateand/ormandatetheadoptionbyindustryaswellasenergyinfrastructureplan-nersofalreadydevelopedbestavailabletechnologiesfordecarbonisationandtomaximisetheuseofcleanenergyinmanufacturingprocesses.Adoptingdecarbonisationtechnologyinamannerthatreducesemissionsgloballywillrequireclosecoordinationofnationalandinternationaleffortsindatacollection,stan-dards,andleadershipintrademechanismdevelopment(seechapter6).KEYACTIONACCELERATEINDUSTRIALELECTRIFICATIONACROSSTHEBUILDINGLIFECYCLE,FROMMATERIALPRODUCERSTOCONSTRUCTORS,OWNERSANDDEMOLITION>Leverageadvancementsinlow-carbonelectricity,bothfromthegridandon-site(ordistrict)renewablepowergenerationsources.>Investinthedevelopmentofneighbourhoodmicro-gridsandpeer-to-peerpowersharingbetweendifferentstakeholders.KEYACTIONACCELERATEMULTIPLEPATHWAYSTODECARBONISATIONINTHECEMENTSECTOR>Increasefundingandprovideincentivesforpublic-pri-vatepartnershipstoacceleratethedevelopment,demonstrationandcommercialisationofconcretedecarbonisationtechnologiesandtechniques.>Investinmaterialssciencecapacityinconcretetechnologyandpractice.>Investinthetransitiontobiobasedcementitiousbindingmaterialsfromagriculturalandforestdetritus.>PromotetheresearchanddevelopmentofCarbonCapture,UtilisationandStorage(CCUS)technologythatcouldreducecarbonemissionsandincreasematerialstrength,therebyreducinguse.>Improvebuildingcodestomandatethedesignandimplementationof‘circular’,modularconcretecompo-nentsthatcanbeeasilydisassembledandreused.KEYACTIONREDUCETHECARBONFOOTPRINTOFTHESTEELMAKINGSECTOR>Encourageupgradesofexistingplantstobestavailabletechnologyinsteelmaking.>Providefinancialandstructuralsupportforphasingoutcoal-basedprimarysteelmakingtechnologies(blastfurnace/basicoxygenfurnaces)withlow-emissiontechnologies(directreducedironcoupledwithelectricarcfurnaces).>Incentivisematerialefficiencystrategiesacrossthe81BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREsteellifecycletoincreasesteel’scircularityandreduceitsembodiedcarbon.>Funddevelopmentanddemonstrationsoftransforma-tionalnewmethodsforCCUS,hydrogensteelproductionandelectrolysisofironore.KEYACTIONINVESTINLOW-CARBONPOWERFORALUMINIUMPRODUCTION,ANDMINIMISEDOWNCYCLING>Sharplyincreasetheavailabilityoflow-carbonelectricityforaluminiumproductiontoreducethehighembodiedcarbonofvirginaluminium.>Incentivisematerialefficiencystrategiesacrossthealuminiumlifecycle.>Improvecollectionandgrade-specificsortingatend-of-lifetomaximisetheuseofscrapinfuturealuminiumproductionwithouttheriskofdowncyclingtolow-valueapplications.>Investinandenablethetransitionofdigitisedoff-sitemanufacturingtogreatlyreduceyieldlossesinmanu-facturing.7.4.2PromotetheTransitiontoLow-Carbon,BiodiverseMaterialsDesigningwithnature-basedprocessesmeansshiftingfrom“extracted”non-renewablesto“grown”renewablesTodecarbonise,thebuiltenvironmentsectormustlearntodesignwithnature-basedprocesses.Thismeansshif-tingfrom“extracted”non-renewablematerialsto“grown”renewablematerials.Thedecarbonisationofthecementsectorandothermajoremitterscanbeenhancedbyshiftingtobio-basedmaterialsandotherlow-carbonreplacements.However,theseemergingmethodsareoftennotyetcostcompetitive,andwidespreadbiasesremainthatprotectentrenchedmethods.Sustainablyscalingupimplemen-tationcannotbeenforcedwithoutsubstantialinvestmentinresearchanddevelopmentalongsideincentivesand/orenforceablebuildingcodes.Therearesubstantialdangersofanunregulatedshifttowardsbiomaterialsbackfiringandcausingunmitigatedenvironmentaldegradation.KEYACTIONPROMOTETHEADOPTIONOFSUSTAINABLEMANAGEMENTANDPRODUCTIONOFBIO-BASEDMATERIALS>Adoptboth“push”and“pull”marketapproachestoscaleupsustainablebio-basedbuildingmaterials,bypushingtocreateconsumerdemandbysupportinglow-carbonbuildingmaterialenterprisesatthelocalandbioregionalleveltodevelopandmarketnewproducts,whilstcultivatingbroadpublicinterestandeducationthroughpowerfuladvertisingandpubliceducationcampaigns.>Createlocaleconomicincentiveschemesacrosstimber,biomassandrenewablebuildingmaterialproducerswhoimprovelocalandregionalbiodiversityconservationandenhancementpractices.>Accelerateinternationalandlocalregulatoryframeworkstonormaliseindustryadoptionofbio-basedmaterials,includingbystandardisingmaterialperfor-mancecriteria,integratingthesematerialsintobuildingcodesandtrainingstakeholdersinthemainstreamconstructionindustry.KEYACTIONFACILITATETHEADOPTIONOFLOCALISED,LOW-CARBONBUILDINGMATERIALS>Facilitateandinvestinindustrialenterprisespromotingtheuseoflocalised,low-carbonearthmasonryandreplacehigh-carboncementitiousmaterialandbinderswithsecondaryandbio-basedbinderswhereverpractical.>Dramaticallyreducetheriskofregionalforestfiresandincreasethecarbonsequesteringproductivityofregionalforestsandagriculturallandsbyfacilitatingeducationandinvestmentinenterprisesfocusedoncollection,incinerationandupcyclingofforest,agricul-turalandbiomassresources.>Promoteinvestmentandincentivisetheuseofby-pro-ductresourcesintheimprovementofconventionalbuildingmaterials–suchasflyashfromcoalandagriculturalindustriesorsewersludgeash.KEYACTIONPROMOTEAWARENESSANDCAPACITY-BUILDINGAMONGBUILDINGPROFESSIONALS>Partnerwithindustryassociationstoeducatebuildingdesignprofessionalsaboutalternative,low-carbonconstructionmaterialsandcomponents(bothvirginandsecondarymaterials),andaboutthepotentialenviron-mentalimpactsacrossthelifecyclewhenselectingmaterialsforabuilding.7.4.3IncentiviseCircularEconomyApproachesforRe-UseandRecycling82BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURERecycledmaterialsarenotyetavailableinsufficientquantitiesandqualitiesDespitegrowingawareness,mostmaterialcyclescontinuetobemorelinearthancircular.Asaresult,non-renewable,energy-intensivematerialsstillsupplythemajorityofdemand.Sofar,recycledmaterialsarenotavailableinsuffi-cientquantitiesandqualities,andthegapbetweensupplyanddemandforrecyclablesisgrowinginmostsectors.Anewsupply-and-demandmodelisneeded,withnewenterprisesthatallowforthecarefuldismantlingofbuildingsandforthestoring,preparationandmaintenanceofsecond-cyclematerialsforresalethatwillenablecirculareconomieswhileprovidingjobopportunities.Indevelopedeconomies,itiscriticaltoimproveindustrymethodstorepurposethemassivequantitiesoffailingconcreteandsteelfrom20th-centuryinfrastructurethatarenearingtheendoftheirfirstlife,sothattheycanbetransformedintomaterial“banks”fornewconstructionandslowthepaceofnon-renewablematerialextraction.Governmentincentives,awarenesscampaigns,andlegalandregulatoryframeworkshaveshowntobeeffectivetoincen-tiviseapproachesforre-useandrecycling(Liu,BangsandMüller2013).Recyclingsystemsforbuildingmaterialstendtorequiresimilarkindsofsupportacrosscountries,includingpromotingmarketsforre-usableproducts,providingincen-tivesforthecreationofre-usecentres(Forrest2021)anddevelopingspecialisedcontractors.Tofacilitatethis,farmoreinvestmentisrequiredforresearchanddevelopmentandforequipmenttorecoverandprocessconstruction,renovationanddemolitionwastematerials.KEYACTIONADOPTDESIGNPOLICIESTOPROMOTECIRCULARITY,RESOURCEEFFICIENCY,LONGBUILDINGLIFESPANSANDZERO-WASTERENOVATION>Incentivisebuildingdesignsthatlastaslongaspossibleand,wherepossible,incorporatedesignfordisassemblyandmodularconstructiontofacilitateend-of-liferecycling.>Adoptrenovationpoliciesthatencouragethediversionofend-of-lifematerialforrecoveryandrecycling,promoteregulationandmeasuringofwholebuildinglife-cyclecarbonemissions,incorporatedesignfordisassembly,andprovidequalitylong-lastingmaterialassembliesinretrofitsolutions.>Promotetheconsiderationofend-of-usestrategiesduringmaterialspecificationinthedesignofnewbuildingsandrenovationsolutionstoavoidwasteandassociatedemissionslaterinthebuildinglife.>Incentiviseamarketplaceformaterialre-useanddevelopstandardstoensurethequalityandefficacyfortheiruse,inordertoprovideassurancetoactorsinthebuildingsector.KEYACTIONINCREASERECYCLINGRATESFORKEYBUILDINGMATERIALS>Targeteconomicincentivestoincreaseoverallrecyclingvolumes,incentiviseefficientcollectionandsortingtocreatecompetitivesecondarymarkets,andputpremiumsonthecleanlinessofrecyclingstreamstominimisedowncycling.>Facilitatestakeholderengagementamongdesignersandrecyclerstoidentifychokepointsandproblemswiththequalityofsupply.>Investinnewequipmentforcollecting,sortingandconvertingsecondarymaterialsonsiteatthetimeofbuildingdeconstructionsothatitcanbeefficientlyrepurposedintoanewlifecyclewithitsvalueretained.>Putinplacemarketincentives(recycledcontent)andregulatoryincentives(collectiontargets)thatensurethatpolymerscollectedfromconstruction,renovationanddemolitionwastearedivertedfromlandfillsandtowardsrecycling.7.4.4PromoteBuildingRe-UseandRenovationInsteadofNewBuildIndevelopedurbanareas,thehighestcarbonsavingstrategyisthepreservationofexistingbuildingstock.Muchcanbedonetopromotethereuseofbuildings,componentsandmaterialsbymodernisingzoningandbuildingregulations,inparticulartoallowforthetransitionofunder-utilisedofficeandcommercialspacestobeconvertedintohousing.KEYACTIONDEVELOPCOMPREHENSIVEADAPTIVEREUSEPROGRAMS>Removeregulatorybarrierstothereuseofbuildingsandcomponents.>Prioritiseandexpediteadaptivereuseprojectswhenprocessingzoningapplications.>Supportthedevelopmentanddistributionoftoolkitsforadaptivereuse.>Developadaptivereusefundingtoencouragetherepur-posingofbuildingsoverdemolitionandconstruction.>Developacomprehensivedistrict-levelplanforthefuturethatincludespreservationstrategies.83BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE7.5EnsureaJustTransition7.5.1CoupleSocialandEnvironmentalJusticeinDevelopingEthicalDecarbonisationPoliciesAjusttransitionmeansthatthebenefitsofagreeneconomyarewidelysharedacrossallsectorsofsociety,ultimatelyadvancingalloftheSustainableDevelopmentGoals(SDGs).Increasingstakeholderengagementandcooperationacrossthelifecycle,fromproducerstodemolitioncompanies,iscriticaltoensu-ringajusttransition.However,acoherentclimatemitigationstrategymustbecoupledwithassertiveregulationoflabourmarkets,andwithoutitajusttransitioncouldfail,asmultiplebuildingmaterialsectorsarealreadysomeofthehighest-at-riskforforcedandunjustlabourpractices.Thetransitiontobio-basedandcircularmaterialecono-miesmayexacerbatetheserisksacrossthesupplychain,especiallyininformaleconomieswherebuildingcodesareextremelydifficulttoenforce.Therefore,itiscrucialthatgovernmentsseisetheopportunityofcouplingsocialandenvironmentaljusticewithfairandvisiblelabellingandcerti-ficationprocessestoraiseawarenessamongconsumers,sincethetwoissuescombinedmayultimatelyhavegreatermarket‘pull’thaneitherissuelabelledseparately.KEYACTIONENGAGESTAKEHOLDERSACROSSTHESUPPLYCHAINBYFUNDINGJUSTTRANSITIONPROGRAMS,LABELLINGANDCERTIFICATION>Anticipateandfundproblemareasforajusttransition,particularlyinconventionalhigh-carbonmaterialsectors.>Highlightandencouragetheresolutionofexistinginequities.>PromotethewidespreaduseofJustTransitionplanningToolkitssuchasbyClimateInvestmentFundsandDesignforFreedom.>Supportindustrytosecureworkersandtheircommuni-tiesaffectedbydownscalingofconventionalprocessesandencouragesynergieswithnewopportunitiesandreplacementmethodsthatarebiobasedorcircular.>Encourageinclusiveandtransparentplanning.7.5.2TackleGenderBiasinBothFormalandInformalBuildingSectorsSustainableDevelopmentGoal5isdedicatedtoendinggenderinequalitythatcreatesimpedimentstoeffectivesustainabledevelopment.Asoutlinedinthe2022reportoftheUnitedNationsSecretary-General,betterenvironmentaloutcomescanbeattainedthroughachievinggenderequalityandtheempowermentofwomenandgirlsinthecontextofclimatechangeanddisasterriskreductionpolicies.Increasedparticipationofwomenindecision-makingandmanagementofregionalnaturalresourcescanresultinmoreinclusiveandequitablegovernanceaswellasmorefavourableconservationoutcomes(UnitedNations2022b).Thereareopportunitiestoaddressgenderandminorityinequalitiesacrossthebuildinglifecycleincludinglanduse,planning,design,construction,managementandend-of-life(seeFIgure7.1).Althoughgenderbiasisprevalentacrossthebuiltenviron-mentsector,ittendstomanifestdifferentlyacrossregions.Intheformalsectors,thetwoprincipalissuestoactonare:1)closingthelargegenderpaygapsthatpersistacrossarchitecture,engineeringandconstructionindustries,(AIA,2020)and2)addressingthedominanceofmeninseniordecision-makingandadministrativeroles.Inmanyinformalconstructionsectors,women’seconomiccontributiontosettlementsremainsunpaid,unrecognisedandunderva-lued.Womenareoftenemployedinthemosthazardous,labour-intensiveandlow-payingjobs,withgenderpaygapsrangingfrom30percentto50percent(Baruah2010).KEYACTIONCLOSETHEGENDERPAYGAPANDIMPROVEWORKINGCONDITIONS>Incentivisegenderinclusioningovernmentcontractsandprioritiseprojectapprovalsforcompaniesthatpromotewomentoleadershippositions.>Createinvestmentfundsforfemalecareerinnovationandpromoteskilldevelopmentamongcasuallabour.>Enforcenationalandmunicipalregulationsforsafetyandimprovedworkingconditionsatconstructionsites.7.5.3ImprovetheTrainingandCapacityBuildingOfferforStakeholdersAlongtheWholeSupplyChain,inBoththePublicandPrivateSectorThesuccessofgovernmentpolicies,financialincentives,regulations,andschemesinreducingcarbonandimprovingtheresilienceofthebuildingsectorwilldependontheavai-labilityofaskilledworkforcetoimplementthesechanges.Theshortageof“green-collar”professionalswithcutting-edgeskillsinenergyefficiency,lowcarbonengineering,andskilledconstructionlabourhasbeenidentifiedinanumberofcountriesasamajorobstacleinimplementingnationalstrategiestocutgreenhousegasemissionsoraddressenvi-ronmentalchanges(InternationalLabourOrganisation,2011).Overall,thechallengeofpromotingandimplementinghighperformingbuildingsliesinthetransitionfromtraditionalconstructionpracticestosustainablealternativesandthelackofskillsisconsideredabottleneckforthegrowthofalowcarbonbuildingsector.84BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREKEYACTIONEMBEDENVIRONMENTALSUSTAINABILITY,RESOURCEEFFICIENCYANDCLIMATERESILIENCEWITHINALLMAINSTREAMLEARNING,INCLUDINGNATIONALCURRICULA,APPRENTICESHIPS,DEGREESANDPROFESSIONALQUALIFICATIONS>Promoteawarenessamongbuildingdesignprofessionalsofalternativelow-carbonconstructionmaterialsandcomponents(bothvirginandrecycledmaterials).>Includetrainingasanintegralcomponentofnationalbuildingandconstructionsectorstrategy,involvingindustryandsocialpartnersinthedesignanddeliveryoftraining,combiningpracticalandtheoreticalknowledge,andtargetinginitiativestowardsmigrantandinformalworkersaswellassmallconstructionbusinesses.>Enhanceknowledgesharing,fostercollaborativecurri-culumdevelopment,encourageexperientiallearningandexchangeprograms,strengthenpartnershipandresourcesharing,providemoretechnicalassistanceandcapacitybuildingsupport,aswellasfundingandincentives.Figure7.1HumansarePartofaLivnigEcosystem:FrameworkfordignityacrossthebuiltenvironmentlifecycleSource:PartiallyadaptedfromInstituteforHumanRightsandBusiness(2022).LANDUSEDueprocessinlandacquisition,respectforindigenousandculturalrights,reducerawmaterialextraction,facilitatingurban-ruralcooperationandenforcingsustainableforestry,agricultural,andafforestationpractices,ensuresafeandfairworkingconditions.PLANNING+FINANCEInvestinnewmaterials,bestavailabletechnologies,andfacilitatecooperationtoincentiviseajust,circular,andbioeconomyacrossthelifecycle.Facilitatecooperationbetweenthebuilding,agrictulral,andforestrysectors.DESIGNPrioritisebuildingmaterials,interiorspacesandurbaninfrastrcturewhichsupportecosystemsdiversity,humanphysicalandmentalhealth,Inclusion,andaccessibility.CONSTRUCTIONConstructionworkers’rights,buldingsafety,responsiblesourcingofmaterials.Prioritisetheuseofmaterialswithcertiﬁcationofbothenvironmentallysustainableandfairlaborproductionpractices.MANAGEMENT+USEProvideopportunitiestoincreasethevalueandrightsofmaintenanceworkersandoccupantsbyreevaluatingtheimporanceofmaintainingmaterialsandlivingsystemsinacircularmaterialeocnomy.CIRCULARITYResponsibledisposal,re-useandreyclingofbuildingmaterials,approachtovacantlandandprojectlegacy.Promotebuildingre-use.HUMANDIGNITY+BIODIVERSITYACCOUNTABILITYPARTICIPATIONNON-DISCRIMINATIONDATATRANSPARENCY85BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE7.6StrengthenInternationalActionandCollaborationforCollectiveImpact7.6.1AddresstheDecarbonisationofMaterialsandEmbodiedCarboninNdcsAttheinternationalclimatelevel,actionisrequiredforcoun-triestoaddressembodiedcarbonintheirNationallyDeter-minedContributions(NDCs)towardsreducingemissionsundertheParisAgreement.Despitethemassivecontributiontoglobalemissionsfromembodiedcarbonwithinbuildingmaterials,ithaspreviouslybeenunder-addressedinstrate-giestoreducebuildingemissions.Thus,relatedactionsandtargetsshouldbeintroducedintoNDCs.KEYACTIONINCLUDESMARTGOALSFORDECARBONISATIONOFTHEBUILDINGSANDCONSTRUCTIONSECTOR>EnsurethatcommitmentsinNDCreflectcoherentpoliciespresentedinthischapter,withakeyemphasisonmaterialsindustrydecarbonisationanddecisionsmadeduringthedesignphase,eitheratthenational,subna-tional,architects,orcontractors/implementerlevels.7.6.2DevelopmentofInternationalTradeMechanismstoEnsureDecarbonisationofEmergingEconomiesInternationalcooperationisrequiredtoregulatefaircerti-ficationandtradeacrossbordersandregions.Labellingstandardsandadequateverificationmechanismsneedtobefairlysupportedacrosseconomiestoreducethewidediscrepanciesinmethodsandquality.Fortruedecarbonisationofglobalmaterialflows,itisnecessarytoclosea“carbonloophole”thatdisadvantagesproducersfromregionswithstrictpollutioncontrolsthatmustcompeteunfairlywithproducerswithmorelaxcontrols.Inturn,itiscriticaltohelpsmallerproducers,espe-ciallyinemergingeconomies,achievecertificationfortheirmethods.Currently,someofthelowest-carbonpracticesarebeingunfairlypenalisedwithcross-bordercarbontaxesbecausetheycannotafford,orlackaccessto,certificationprocesses.Developmentsininternationaltrademechanismsmaybeabletochangethegameincombatingglobalclimatechange.Foremergingeconomiesthathistoricallyhavecontributedverylittletotheimpactsofclimatechange,butwherethemajorityoftheproductionandconsumptionofmaterialswilloccurinthecomingdecades,itiscriticaltofacilitatethedevelopmentofaconsistentandcomprehensiveaccountingsystemtoaccuratelymeasureemissionsallalongthelifecycleandvaluechain.Thiswillenablethesecountriestohaveafairchancetodemonstratetheircarboncompetitive-nessintheirowndomesticbuildingbooms,aswellasintheproductionofmaterialsforexport(CCSI,IIEDandIISD2021).Forpolicymechanismstocreateatrulylevelplayingfieldtowardsdecarbonisation,manyemergingeconomiesthatsofarhavenotcontributedgreatlytoclimatechangehavetakenthepositionthattheyshouldreceiveasignificantportionoftheproceedsfromcrossbordercarbonadjustmentmechanisms,forexample,tosupportthemintheadoptionoflow-carbonproductionmethodsandcertifications.KEYACTIONPROMOTECLEARANDCONSISTENTSTANDARDSFORCARBONLABELLING>EnsurethatregulationandenforcementofdomesticcarbonlabellingmatchesISOstandards.>Establishaninternationalstandardscommitteeforcarbonimpactlabellingofbuildingmaterialstoaddressdiscrepanciesinmethodsandqualityandcreatepathwaystowardsenforceableregulation.>Closethe“carbonloophole”incarbonoffsetsbydeve-lopingaslidingscaleofrelevance,wherebytheprocessmostcloselyassociatedwiththeactualdecarbonisationofmaterialprocessesgetsthemostcredit.>Developtrademechanismstosupportemergingeconomies.>Ensureafairplayingfieldforlow-carbonbuildingmate-rialsthroughinternationalandmultilateralengagement.©Chuttersnap/Stocksnap86BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURE878CONCLUSIONAndDiscussion88Tomitigatedangerousongoingclimatechange,itiscriticaltomoveaggressivelytodecarbonisethebuiltenvironmentsector.Acrossregions,methodswillvaryinimplementingthethreemaindecarbonisationprinciplesoutlinedinthisreport:1)Avoidingnon-renewableextraction,2)Shiftingtobio-basedsustainablematerials,and3)Improvingconven-tionalbuildingmaterialsandprocesses.Materialflowscenariosfordevelopedversusdevelopingcountrieshighlightkeydifferences.Indevelopedcountries,thefocusshouldbeonincentivizingtherenovationofexistingandageingbuildingstocktotransitiontohigh-performancebuildings.Indevelopingcountries,rapidurbanisationunder-scorestheneedtosetandthenenforceperformance-basedbuildingenergycodesfornewconstruction,startingwiththepublicsectortosetthestandard.Inemergingeconomies,policiesthatfocusonthedecarbonisationofthebuiltenvi-ronmentsectormustalsoaddresstheneedsoftheinformalandsemi-formalconstructionsectors,wherethebulkofthelabourforceresides.Reducingembodiedcarboninbuildingmaterialstonetzeroisachievableby2050,ifwepromotetheuseofbestavailabletechnologiesforconventionalmaterials,combinedwithamajorpushtoadvancetheupcyclingofbiomaterialsfromforestandagriculturestreams.Thegreatestpotentialtodecarbonisethesectorlieswiththeabilitytomanagecarboncyclesbyremovingmaturetreesanddecayingforestandcropresidues,inordertostorethecarbonwithinbuildingmaterialsandproducts.Thiswouldproducecompoundingbenefits,fromreducingtheriskofforestfires,toincreasingtheproductivityofforestedlandtracksthroughrejuvenationandresponsiblereforestation–therebyincreasingthecarbonuptakefromforestswhilereducingclimatechangeemissionsfromtheburningofcropwaste.Theincreaseduseofproperlymanagedbio-basedmate-rialscouldleadto40percentemissionsavingsinthebuiltenvironmentsectorby2050inmanyregions,evenasthetransitiontolow-carbonconcreteandsteeloccursinparallel.Increaseddemandfordecarbonisedbio-basedmaterialscouldincreasethecarbonuptakeofresponsiblymanagedforestsinsomeregionsbyupto70percentby2050,comparedtobaselinescenarios.Supportingtheuseofallbestavailabletechnologieswillgreatlybolstertheeffort,THEBUILTENVIRONMENTPROCESSISCOMPLEX.TECHNOLOGYANDBIGDATAHAVEACRITICALROLEINHELPINGTOESTABLISHCOLLABORATIVENETWORKS,WITHEFFICIENTCONSTRUCTIONPRACTICESTHATTRACKMATERIAL,ENERGYANDINFORMATIONFLOWSACROSSBUILDINGLIFECYCLESANDGLOBALECOSYSTEMS.©ShigeruBan89BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREbutsubstantialresearchanddevelopmentisstillrequiredtodeploymoresustainablemethodsforbio-basedmaterials.Thisisespeciallytrueintheareaofgreenchemistryforbinders,gluesandtreatmentsthatenableforestryandagriculturalby-productstobeengineeredintostructuralsystems.Theincreaseduseofproperlymanagedbio-basedmaterialscouldleadto40percentemissionsavingsinthebuiltenviron-mentsectorby2050inmanyregions,evenasthetransitiontolow-carbonconcreteandsteeloccursinparallel.Increaseddemandfordecarbonisedbio-basedmaterialscouldincreasethecarbonuptakeofresponsiblymanagedforestsinsomeregionsbyupto70percentby2050,comparedtobaselinescenarios.Supportingtheuseofallbestavailabletechnolo-gieswillgreatlybolstertheeffort,butsubstantialresearchanddevelopmentisstillrequiredtodeploymoresustainablemethodsforbio-basedmaterials.Thisisespeciallytrueintheareaofgreenchemistryforbinders,gluesandtreatmentsthatenableforestryandagriculturalby-productstobeengineeredintostructuralsystems.Reducingtheextractionofnon-renewablematerialsisfurtherbolsteredbythedevelopmentofcirculardesignforre-useandrecycling,alongsidetheelectrificationofallprocesseswithrenewableenergyandthedevelopmentofat-plantcarboncaptureandstoragetoincreasematerialstrengthbyupto30percentinsectorssuchascement.Reducingmaterialusethroughdata-drivendesignoptimi-sationtosupportthetransitiontosustainablematerialsandsystemsthatarederivedfromrenewablebio-basedsourcessuchastimber,bambooandagriculturalbiomasswillrequiremorecomplexinformationmanagementandcommunicationacrossstakeholders.Policiesneedtosupportthedevelop-mentofaccessibleanalyticaltools,buttheyalsoneedtomandatetheirusethroughbuildingcodes.Inpursuingthesestrategies,thereareimportantco-benefitstoconsider,aswellasrisks.Inparticular,envisioningandimplementingalarge-scaletransitiontocircular,bio-basedmaterialsinthebuiltenvironmentcarriessubstantialrisksifthechangestothebroaderecological,socialandeconomiccontextarenotplannedforandhandledverycarefully.Decarbonisationofbuildingscreatesrisksofunintendedconsequencestotheecosystemsthatunderpintheproduc-tiontosupplythealternativebio-basedmaterials.Itcanalsoleadtotheperpetuationorexacerbationofunjustlabourpractices,andtoinequitableshiftsineconomicgainsandlossesasindustriestransition.Thereportemphasisestheneedtotakeawhole-lifecycleapproachwhenassessingstrategiestodecarboniseemis-sionsfromthebuiltenvironment.Whentakingsuchanapproach,theworkofthegeo-biospheretoproducespecificlocalnaturalresourcesisvalued.Therefore,theuseofbio-basedandrenewablematerialssuchastimber,bambooandbiomassproductsmustbesupportedwithregulationstoprotecttheecosystemsthatsustainthoseresources,withcarefulconsiderationofregionallyspecific,sustainablelanduseandforestmanagement.Inordertogalvanisethemarketandtoenabledesigners,buildingowners,andcommunitiestomaketherightdecisions,toolstosupportthedecarbonisationofbuildingmaterialsrequiremorerapidprogress.Thesetoolsmustbesupportedbyaccesstobetterqualitydataandtransparentauditsconductedbyqualifiedthird-partyreviewers.Moresynergycouldbeleveragedincombiningthecertificationoffairlabourandenvironmentalpractices/workingconditions.Intheinformalsectors,stakeholderstypicallyhaveneithertheaccesstodatanorthemeanstoconductanalysesorcertification,thusgreatlydisadvantagingbothproducersandbuildersinemergingeconomiesfromdecarbonizingtheiroutput,forbothlocalandexportmarkets.Thus,internationalcooperationiscriticaltosupportfaircertificationandlabelling.Suchpoliciescanbesynergisticwithimprovingstrategiestodecarbonisetheembodiedenergyofmaterialswithintheformalsectorsacrosstheglobe,asthesearethesectorsthatareconsumingandproducingthemajorityofcarbonemissionsinthebuiltenvi-ronmenttoday.Ultimatleytheresponsibilityforgalvanisingafuturenetzeroeconomyforthebuiltenvironmentsectorshouldbespreadacrossproducersandconsumerswithintheformalglobalbuildingsector,bothpublicandprivate.90BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREPOLICYMAKERSFINANCIALINVESTORS+DEVELOPERSMANUFACTURERS,BUILDERS+WASTEMANAGERSARCHITECTS,ENGINEERS+OCCUPANTSWORKOFTHEGEO-BIOSPHERE>Policiestoreduceextractionofnon-renewablematerials>Facilitateinnovationinbiodiverse,circularforestry+agriculture>Useeconomicpracticesthatvaluenaturalcapital+biodiversity>Committogenderequity+fairlabouracrossprojectlifecycles>Avoidunsustainableland-usepatterns,soildegradation+forestrypracticesinsourcingbothconventionalandbiomaterials>Considerthesource+recoveryrateofnon-renewable+renewablematerialswhendesigningmaterialsDESIGN>Enforceperformancebasedbuildingcodes>Developfairgreencertificationsandtransparentlabeling>Incentivizetoolsfordata-drivendesign>Investindesignofrecycled,re-used+bio-basedmaterialsandcomponents>Investinaccessibledatavisualizationframeworks>Committothedevelopmentofcircularcomponents>Developmaterialstooptimizerecyclability>Developbio-basedalternatives>Designforlongerlife>Increaseeducationindecarbonisationstrategies>Computation/design/optimizationoflocalmaterialsforre-usePRODUCTION>Electrifythegrid>Mandaterecycling+BestAvailableTechnologies(BAT)>Mandateforest+materialmanagement>Improvecertifications>Investininnovationforlow-carbonmaterials+binders>Investinnewlow-carbonmethods>InvestinBATequipment>Upgradeplants>Avoidprimarymaterials>Circularmanufacturing+compositesforre-use>Committofairlabour>Workwithproducerstospecifycircularmaterials>Designdevelopmentofalternativebiomaterials+componentsCONSTRUCTION>Mandategreencertifications>Mandatethirdpartyverificationofsiteprocesses+emissions>Incentivizeoff-sitecircularmanufacturing>Increaseenergy-efficientfinancing>Improvefinancingforrefurbishment+renovationofexistingbuildingsandmaterials>Committofairlabour>Tracematerialuse>Electrifyallequipmentwithrenewableenergy>Requireenergy-efficiency>Improvetraining>Committofairlabour>Manageon-sitewastethroughpre-fabrication>Improvemanagementofon-siteconstructionwithcirculardesignUSE>Buildingenergycodesthatmandatematerialselectionforhigh-performancebuildingenvelopestoreduceoperationalcarbon>Incentivizerenovationovernewconstruction>Financialtoolstoincentivizelowcarbonmaterialselectionbyreconizingenergy+costpaybackperiods>Supportbuildingowners+occupantstoselectlowcarbonalternativesthroughsupplychaindevelopment>Increasemateriallifewithlow-carbonmaintenancepractices>SelectmaterialsthatreduceoperationalcarbonENDOFUSE>Certifypre-usedcomponents>Buildingcodestomandatere-use>Cityplanningoftransferplants>Regulatedemolition>Provideeconomicincentivestoavoiddemolitionbyrefurbishingbuildings,increasingre-use+recycling>Improverecovery+on-sitesortingofmaterials>Standardizematerialstoimproverecycling>DesignforDissasembly+Re-Use>Increasecontinuingeducationforstudents+professionalsinnovelcircularmaterialstrategiesTABLE8.1BUILDINGLIFECYCLEPHASESWHODOESWHATTODECARBONISEMATERIALS?91BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREBIBLIOGRAPHYAbid,R.,Kamoun,N.,Jamoussi,F.andElFeki,H.(2022).FabricationandpropertiesofcompressedearthbrickfromlocalTunisianrawmaterials.BoletíndelaSociedadEspañoladeCerámicayVidrio61(5),397-407.https://doi.org/10.1016/j.bsecv.2021.02.001.Adinkrah-Appiah,K.andObour,G.D.(2017).Fusedlateritepowdersubstitutionforcementinconcreteproduction.InternationalConferenceonAppliedScienceandTechnologyConferenceProceedings:3(1),100-105.http://102.223.173.31/icast/index.php/proceedings/article/download/25/22.AfricanOrganizationforStan-dardization(2018).Compressedstabilizedearthblocks–requirements,productionandconstruction.https://www.arso-oran.org/wp-content/uploads/2014/09/WD-ARS-1333-2017-Compressed-stabilized-earth-blocks-Requirements-production-and-construction.pdf.Agarwal,B.(2010).GenderandGreenGovernance:ThePoliticalEconomyofWomen'sPresenceWithinandBeyondCommunityForestry.Oxford:OxfordUniversityPress.Agarwal,B.(2015).Thepowerofnumbersingenderdynamics:illustrationsfromcommunityforestrygroups.JournalofPeasantStudies42(1),1-20.https://doi.org/10.1080/03066150.2014.936007.Akbarnezhad,A.andXiao,J.(2017).Estimationandminimizationofembodiedcarbonofbuildings:Areview.Buildings7(4),5.https://doi.org/10.3390/buildings7010005.Albertsson,A-C.andHakkarainen,M.(2017).Designedtodegrade.Science358(6365),872-873.https://doi.org/10.1126/science.aap8115.Allwood,J.M.(2013).TransitionstomaterialefficiencyintheUKsteeleconomy.PhilosophicalTransactionsoftheRoyalSocietyA:Mathematical,PhysicalandEngineeringSciences371(1986),20110577.https://doi.org/10.1098/rsta.2011.0577.Allwood,J.M.,Ashby,M.F.,Gutowski,T.G.andWorrell,E.(2013).Materialefficiency:Providingmaterialserviceswithlessmaterialproduction.PhilosophicalTransactionsoftheRoyalSocietyA:Mathematical,PhysicalandEngineeringSciences371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tute2022).Thepropertiesofthefini-shedcementdependontheratioandselectionoftheblendingmaterials,whichcanbroadlybeclassifiedasprimaryversussecondarycementitiousmaterials(Shahetal.2022).Primarycementitiousmaterialsincludelimestone,naturalvolcanicmaterials,andkaoliniteandcalcinedclays(includingcalcinedclaylimestoneorLC3)(Scriveneretal.2018a),whilesecondarycementitiousmaterialsincludeindustrialby-pro-ductssuchascoalflyashandsteelblastfurnaceslag.Theyalsoincludebio-basedashes(mostlyby-productsfromagriculture,suchasricehuskorcassavapeel,aswellasfromforestry)andend-of-lifematerials(mostlybinderfromconstructionanddemolitionwastes,butalsopozzolansfromrecycledglass)(seeFigureA.2).Thetypeofsupplementarycementitiousmaterialthatcanbeuseddependsonthelocalcontext(seeFigureA.3),suchastheplantcapacity,themoisturecontentandburnabilityoftherawmaterials,theavailabilityofblendingmaterials,thereliabilityofsupplychains,aswellasnationalcementstandards.However,amajorimpedimenttowidespreadadoptionofmanyalterna-tive,“circular,”secondarycementitiousmaterials,particularlythebio-basedoptions,isthevariableperformanceandlackoflocalcertification.103BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREFigureA.3aAvailabilityofalternativecementitiousbindersbyregion,2018MostcountriescouldgeneratesufficientsecondarycementitiousmaterialstosubstituteforPortlandcement.Source:Shahetal.2022.Endoflife-CMsIndustrial-CMs<12.5%>100%Nocementproductionreported12.5-25%25-37.5%37.5-50%50-62.5%62.5-75%75-87.5%87.5-100%104BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREFigureA.3bAvailabilityofalternativecementitiousbinders,byregionandtype,2018Source:Shahetal.2022.Agricultural-CMsForestry-CMsEndoflife-CMsIndustrial-CMs<12.5%>100%Nocementproductionreported12.5-25%25-37.5%37.5-50%50-62.5%62.5-75%75-87.5%87.5-100%105BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREANNEX3MATERIALFLOWSFORSTEEL,ALUMINIUMANDGLASSFigureA.4SteelmaterialflowsMorethanhalfoftheworld’ssteelisusedintheconstructionofbuildingsandinfrastructure.Note:Circularmaterialflowsdominatepost-fabrication,withlittlereturningintotheglobalflowofsteelafterend-useproducts.Source:Cullen,AlwoodandBambach2012.106BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREFigureA.5Globalflowsofaluminium,2007Aluminiumisproducedusingprimaryminedmaterialsand,toalesserextent,scrap.Note:Thefigureshowstheflowofaluminiumfromproduction(ore-based,top,andscrap-based,bottom,greyflows)toenduses,withtheconstructionandassociatedsectorshighlighted..FigureA.6GlobalmaterialflowandendusesofglassGlobalglassproductionisdividedintocontainerglass(forfoodandbeverages)andflatglass.Source:Westbroeketal.2021.107BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREANNEX4COUNTRYCASESTUDIESOFTHE“AVOID-SHIFT-IMPROVE”STRATEGIESGlobally,countrieswithverydifferentbuiltenvironmentcontextscanpursuedecarbonisationoftheirbuiltenvironmentsectorsusingthe“Avoid-Shift-Improve”strategies.CANADADominantmaterials:>Concreteandsteel(commercial)>timber(residential)Currentstatus:>Canadahasoneofthecleanestgridsforglobalmanufac-turing(82percentemissions-free)andusesmorethan70percentlesscarbonthantheglobalaverageforsteelandaluminium(EnvironmentandClimateChangeCanada2022).However,theelectricityismostlyfromhydro-power,andfurtherproposedexpansionofdamsisbeingchallengedfordegradingenvironmentalandindigenousrights.>Timberisre-emergingtoreplaceconcreteandsteelintheresidentialsector,andthereareworld-firstdemonstra-tionsformassivetimberuseinhigh-riseconstruction,butfurtherdevelopmentofsustainablebindersisnecessary.Policyrecommendations:AVOIDprimarymaterialsandmovetoacirculareconomy>ConstructionrepresentsacoresectorforadvancingthecirculareconomyinCanadaduetoitseconomicimpor-tance,highmaterialnecessityandlargequantitiesofwaste(CouncilofCanadianAcademies2021).SHIFTtobio-basedmaterials>Improvesustainableforestrypracticesifwoodresourcesaretobemoreindemand.>Useamixoftimberspeciestoavoidamonocultureinforestry(forexample,whitesprucemonocultureshavereplacedAcadianforest,leadingtoreducedbiodiversity,diminishedecosystemfunctionandnegativeculturalimpactsforIndigenouspeople(GovernmentofCanada2021).>Mandateincreaseduseofagriculturalcovercropsandby-productsforbuildingmaterials.IMPROVEconventionalmaterialsandprocesses>EstablishaCleanInfrastructureChallengeFundtopromotepublicprocurementanddemonstrationofdecarbonisationpractices.>Promotelocal,Canadian-madeproductssuchasPortlandlimestonecement,whichcontainsupto10percentlessembodiedcarbonthanimportedcementandwouldavoidmorethan1milliontonsofcarbonpollutioneachyear.FINLANDDominantmaterials:>Concrete>Timberandwood(residential)Currentstatus:>HasreduceditsemissionsatafasterpacethantheEuropeanUnionaveragesince2005,withthelargestreductionsinmanufacturingindustriesandconstruction.Thesector’sshareoftotalemissionsfellfrom16percentin2005to11percentin2019(Jensen2021).>Hassomeoftheworld’smostambitiousbuildingcodesthatsupportthetransitiontobio-basedmaterialsandnetzerourbanemissions.>Initiatedtheuseofneighbourhood-levelcarbonplanningtools(AVA).Policyrecommendations:AVOIDprimarymaterialsandmovetoacirculareconomy>Adoptpoliciesandtargetsatthemunicipalandnationallevelsforintegrateddecarbonisationacrossmultiplescalesofinfrastructureandbuildings.>Usecarbontrackingtoolsatthelevelofurbanplanningandregionalecosystems.SHIFTtomoresustainablebio-basedmaterials>Furtherdevelopsustainableforestrypractices,aswoodresourcesareinhighdemand,butoverharvestingofrawtimberneedstobereplacedwithmoresustainablepractices.>Scaleupthedevelopmentanduseofagriculturalcovercropsandby-productsforbuildingmaterials.IMPROVEconventionalmaterialsandprocesses>Improvedatacollectionmethodsforbuildingmaterialsandprocesses,especiallytopromotere-useofmaterials.>Buildsystemstocollectdataonoperationalenergycostsandcreateplatformsforuserstotrackenergycostsofmaterialdecisions.108BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREGHANADominantmaterials:>Concretemasonry>Metals(roofing)Currentstatus:>Theshareofconcretemasonryusedforexternalwallconstructionhasrisenfrom39percentto64percentsince2000(GhanaStatisticalService2021).>Metalsheetscomprise80percentofallhousingroofingapplications(GhanaStatisticalService2021).>Useoflow-carbonearthmasonryforwallconstructiondeclined50to30percentsince2000(GhanaStatisticalService2021).>TimberloggingisanestimatedtwotothreetimesabovethelegalannualallowablecutssetbytheGhanaForestryCommission(Oduro2016).>Theelectricitysectorhasshiftedsharplyfrom64percenthydropowerin2015to66percentfossilfuel-basedin2020(Ritchie,RoserandRosado2020).Policyrecommendations:AVOIDprimarymaterialsandmovetoacirculareconomy>Investinandmarketlocalbuildingmaterials,withafocusonthepartialorfullsubstitutionofconcretemasonryproductsaswellasimprovedinfrastructuretorecoverhighratesoflocalmaterialwasteinthetimberandagri-culturalsectors.>Provideresearchsupportandindustrialincentivestoencouragetheuseoflocallyavailableandlow-carbonalternativestoPortlandcementbindersinconcretemasonryproducts.SHIFTtobio-basedmaterials>Progressivelyreviselocalbuildingcodesandstandardstoincludenear-terminstallationandperformanceguidelinesforlow-carbon,bio-basedandearthmasonrymaterials.>Revisethebuildingpermitprocesstorequiremandatoryminimumvaluesforroofinginsulation.>Provideprofessionaltrainingandupskillingintheuseoflow-carbon,bio-basedandearthbuildingmaterialsacrosstheagriculture,manufacturing,design,construc-tion,artisanalandwastemanagementsectors.IMPROVEconventionalmaterialsandprocesses>Progressivelyreviselocalbuildingstandardsandcodestoincludematerialspecificationsforembodiedcarbonandclimateperformance.>Enactgreenprocurementpoliciesthatsupporttheuseoflow-carbonandlocallyavailablebio-basedalternativesasaggregates,binders,reinforcingcomponentsoradditivesacrossmasonryandtimberproducts.GUATEMALADominantmaterials:>Concreteblockandsteel>Earth-basedandbiomassmaterials(vernaculartradi-tions)Currentstatus:>InGuatemala’sboomingresidentialconstructionsector,between2002and2018,theuseofcementblockincreased96percent,concrete215percentandmetal191percent;meanwhile,theuseoftraditionalmuddeclined38percentandtheuseofagriculturalandforestby-pro-ductmaterials(straw,sticks,orcanes)fell29percent(GuatemalaINE2002).Policyrecommendations:AVOIDprimarymaterialsandmovetoacirculareconomy>Establishnationalbuildingcodeswithregionalcompliance,andprogressivelyreviselocalbuildingstan-dardsandcodestoincludeembodiedcarbonandclimateperformance.>Supportnationalandregionalschoolsinarchitecture,engineeringandindustrialdesigntofocusonthetran-sitiontocircularprinciplesformodularpre-fabricatedconcretecomponents,andencouragedesignfordisas-semblyandre-useofcomponents.SHIFTtobio-basedmaterials>Developstandardsandconductcertificationsofregionalandtraditionalearth-basedandbio-basedstructuralandadditivematerialsbasedonlocalspecies,toengenderconfidenceinthesematerialsformulti-storeyconstruc-tionamongbuilderswhoneedtodensifyurbansettle-ments.>Facilitatecooperationamongsmall,localandlarge-scalecementindustryplayersandregionalagriculturalprodu-cersindevelopingnovel(bio-based)concreteadmixturestoreducebinderrequirements,whilealsocapitalisingonandupcyclingproblematicbiowastefromregionalagriculture.>Developstandardsforproductionandregulationofregionalbamboo,forestby-productsandbiomass.IMPROVEconventionalmaterialsandprocesses>Facilitatedomesticpartnershipswithmultinationalproducerstowardsestablishingnetzerocementproductionbasedonbestavailabletechnologiesbyelectrifyingwithrenewables.>CapitaliseontheregionalmomentumofCEMEXandotherstowardsfurtherresearchanddemonstrationofcarboncaptureandstorageatcementmanufacturingplants,withrenewableelectrification.109BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTUREPERUDominantmaterials:>Concreteandsteel(urbanhousing)>Earth-basedmaterialsandbio-basedmaterials(ruralhousing)Currentstatus:>Inurbanandruralareas,thereisashifttowardsconcreteandsteelconstruction,replacingtraditionaladobe,mudwall,woodandcanebuildings.Thesenewconstruc-tiontechniquesoftendonotrespondtolocalclimateandbuildingtraditions.Seismicconstructionisacrucialconsideration.>Around66percentofresidentialconstructioninPeruisintheinformalsector(EspinozaandFort2020),whichintheconsolidationphaseemploysmineral-basedmaterials.Policyrecommendations:AVOIDprimarymaterialsandmovetoacirculareconomy>Incentivisetheadaptivere-useofexistingbuildingsanduseofcircularmaterialswithbettercreditsystemsandlabels.>Fortheinformalhousingsector,supporttheparticipationofarchitectsandengineersandthetrainingoflocalpopu-lationsintopicssuchasdesignfordisassemblyandtheuseoflow-impactandlocalmaterials.>Supportdigitalizationasanopportunitytoreducewasteproduction(currentlyusedmainlyinlargeprojects).>Localgovernmentsshouldprioritizetheresearchanddevelopmentofdesignfordisassemblystrategiesforstructuralelements.SHIFTtobio-basedmaterials>Promotesustainableconstructionpracticesbyemployingbiodegradablebiomaterialsandprioritizingsourcingrawbiomaterialswhilepreservingvernaculararchitectureinruralareas.IMPROVEconventionalmaterialsandprocesses>Encourageresearchanddevelopmenttotransitiontraditionalseismicmaterialstowardsloweremissionsandre-evaluatelocalconstructiontechniquesthroughtechnologytransfer.>Supportjobcreationopportunitiesattheend-of-usephase,fromformalisingexistingrecyclerstocreatingnew,formaljobsrelatedtotheconstructionindustry.>Implementmoretransferplantsincitiesandallowurbanlandfillstoreceiveconstruction,renovationanddemoli-tionmaterials,topreventillegaldumpingsites.>Improvecertifications,creditsandlabels.INDIADominantmaterials:>Bricks,concreteandsteel>Rammedearthandmudbrick(ruralareas)Currentstatus:>India’sgreenbuildingmarketdoubledinthefouryearsbetween2018and2022,drivenbyincreasingawarenesslevel,environmentalbenefitsandgovernmentsupport.>Bricksandtraditionalmaterialsstillplayasignificantroleinruralareas,butwithrapidurbanisation,cementandconcretehavebecomethemostcommonlyusedconstructionmaterialsinIndia,accountingforover80percentofthetotal.>TheIndiangovernmenthaslaunchedseveralinitiativestopromotesustainableandeco-friendlybuildingmaterials,inordertousesecondarycementitiousmaterialssuchasflyashinbricksandgreenconcrete.>Womencompriseonly12percentofthebuildingsectorworkforce,mostlyintheleastdesirablejobsintheinformalsector,withagenderpaygapofbetween30and40percent.>Theuseofpre-fabricatedconstructionmaterialsisgainingpopularityinthecountryduetothehighermaterialefficienciesandloweron-siteemissionsanddisruption.Policyrecommendations:AVOIDprimarymaterialsandmovetoacirculareconomy>Establishenforcedpoliciesthatrequirecompaniestouserecycledmaterialsintheirproductionprocessesandtodesignproductsforre-useorrecycling,whichwouldreducewasteandresourceconsumption.SHIFTtobio-basedmaterials>Addresssupplychainchallengesbypromotingupcyclingofwastefromfoodcropsthatcanbeusedasbio-basedmaterialsandbyencouraginginvestmentintheproces-singandmanufacturinginfrastructureforbiomaterials.>Focusonlocalneedsbysupportingresearchanddeve-lopmentofbio-basedmaterialsthataddressspecificchallengesfacedbycommunitiesinIndia;addressnega-tiveperceptionsthroughdesignandmarketing.IMPROVEconventionalmaterialsandprocesses>Strengthenenvironmentalregulationstoreducegreen-housegasemissionsandresourceconsumptioninthemanufacturingsectorusingregulationsonenergyeffi-ciency,wateruseandwastedisposal.>Implementtaxincentivesandsubsidiesforcompaniesthatuselow-carbonmaterialsintheirproductionprocesses.110BUILDINGMATERIALSANDTHECLIMATE:CONSTRUCTINGANEWFUTURESENEGALDominantmaterials:>Concretemasonry>Metal(roofing)Currentstatus:>ConcretemasonryinSenegalaccountsfornearly70percentofwallconstructionand71percentofroofingmate-rials(PEEB2021b).>Metalsheets(38percent)areslightlymoreprevalentthanconcretemasonry(32percent)inruralroofingassem-blies(ANSD2021)>Only5percentoflocaltimberdemandismetbylocalproduction,fromthreatenedtreespecies(Berthome,SilvertreandKouame2013).>Althoughfossilfuelssupply86percentofelectricity,thesupplyfromrenewablesourceshasincreased(6percenthydropower,6percentsolar,0.33percentwindandotherrenewables)(Ritchie,RoserandRosado2020).Policyrecommendations:AVOIDprimarymaterialsandmovetoacirculareconomy>Progressivelyreviselocalbuildingstandardsandcodestoincludeembodiedcarbonandclimateperformance.>Provideresearchsupportandindustrialincentivestoencouragetheuseoflocallyavailableandlow-carbonalternativestoPortlandcementbinders,includingsupplementarycementitiousmaterialstoimprovethestabilisationandhygrothermalperformanceofmasonryproducts.SHIFTtobio-basedmaterials>Investinlocallyavailablelow-carbonfuelsforcementproduction.>Enactgovernmentmandatespromotingtheuseoflocalbio-basedandearthmasonryingreenpublicprocure-mentprojects.>Educatefinanceandinsurancecompaniesworkinginthebuildingsectoraboutthepositiveimpactsoflow-carbonbuildings,andpro-activelyincentivisebuildingownerswhoadoptsuchtechnologies,inassociationwithstandardssuchastheAfricaResearchandStandardsOrganisation’srecentlyratifiedcompressedearthblockstandard(ARSO2018).IMPROVEconventionalmaterialsandprocesses>Promotefinanceandindustrialinvestmentintheresearchanddevelopmentoftechnologicalinnovationofcement,metalandtimberproductsthatareconsistentwithlowgreenhousegasemissionsandresilientlocalbuildingmaterialsectors.©WorofilaUnitedNationsAvenue,GigiriP.O.Box30552,00100Nairobi,KenyaTel.+254207621234unep-publications@un.orgwww.unep.org

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