Rethinking Timber Buildings

RethinkingTimberBuildings Sevenperspectiveson theuseoftimberinbuildingdesignandconstruction Foresight,ResearchandInnovationisArup’sinternalthink-tankandconsultancy whichfocusesonthefutureofthebuiltenvironmentandsocietyatlarge.Wehelporganisationsunderstandtrends,explorenewideas,andradicallyrethinkthefutureoftheirbusinesses. Wedevelopedtheconceptof‘foresightbydesign’,whichusesinnovativedesigntools andtechniquesinordertobringnewideastolife,andtoengageallstakeholdersinmeaningfulconversationsaboutchange. Formoreinformationonourforesightpublicationsandservices,pleaseemailforesight@arup.com. Tocontactourglobaltimberteam,pleaseemailtimber@arup.com. March2019 Coverimage:©MurrayFredericks 13FitzroyStreetLondonW1T4BQarup.comdriversofchange.com ©Arup2019 Contents Foreword4 Preface6 Introduction8 1.Managingourcarbonbudget14 2.Urbandensification24 3.Woodandwell-being32 4.Thefutureisprefabricated42 5.Sustainablesourcing54 6.Knowingthematerial64 7.Innovatingwithwood74 Conclusion84 References91 Acknowledgements99 TimSnelsonAssociateDirectorLondon Above:MetropolParasol,Seville,Spain. Foreword Urbanisationandhumanpopulationgrowthareincreasingthepressureonourplanet’spreciousresourceswithvisiblesignsofanthropogenicdamage.Itisestimatedthattwobillionsquare metresofnewbuildingstockareneededeveryyearbetween2019and2025,especiallyforhousing.Globalcarbondioxideemissions(CO2)haveincreasedbyalmost50%since1990.Theconstruction industryaloneproducesaround15%oftheseglobalemissions. Thereisanurgentneedtolimitglobalwarmingto1.5°Ctopreventtheworstimpactsofclimatechange,asstatedintheIntergovernmentalPanelonClimateChange(IPCC)specialreportonclimatechangereleasedinOctober2018.Thisstrategyrequiresgreenhousegasemissionstobecuttonetzerobyaround2050.Netzeroisthepointatwhichgreenhousegasemissionsarebalancedbytheremovalofthesegasesfromtheatmosphere. Anintermediatetargetof45%reductionby2030isalsorecommended.Weallneedtotakeresponsibilitytomakechangestoenergysystems,changestothewaywemanagelandandchangestothewaywemovearoundwithtransportation.Wealsoneedaradicalrethinkinourapproachtoconstructiontodeliver anetzerobuiltenvironment. Timberisoneofourmosttraditionalconstructionmaterialsandhasakeyroletoplayonbothsidesofthenetzerobalance.Forestenhancementisseenbymanygovernmentsasacrucialpartoftheiremissionsmitigationstrategy,astreesabsorbcarbonfromtheatmospheretogrow. Timberisalsolesscarbonintensivetomanufacture,transportanderectthansteelandconcretestructures.Therefore,increasingtheuseoftimberinourbuildingswillreducethecarbonimpactofconstruction.Athrivingsustainableforestrysectoralsocontributestothenon-urbaneconomy,reducingurbanisation. Thetimberindustryhasbeenenjoyingsignificantgrowthinthelastdecade,primarilyduetotheincreaseinmasstimberproductssuchascross-laminatedtimber,glulamandlaminatedveneerlumber,aswellasmanyboardproductssuchasOSB,thatmakeuseofsmalleroffcuts.Yettimberasastructuralmaterialseemstoinvokeamoreemotiveresponsethanitscompetitors,dividingopinionsandstiflingthemuch-neededdebateonhowandwheretimbercanbestbeusedtosafelydeveloplow-carbonbuildings;namelybyaddressingfurther researchneedsinrelationtofiresafetyperformance,floordynamics,robustnessanddurability. Thiswide-rangingreportexploressevendifferentperspectivesontheuseoftimberinbuildingdesignandconstruction.Ihopeitinformsdebateandmovesthediscourseforwardontheincreasinguseoftimberaspartoftheconstructionindustry’sconcertedendeavourtobuild asafe,resilientandnetzerofuture. Preface Thisreportisintendedforanyonewanting astrategicoverviewoftimberconstructionanditsrecentupsurgeinpopularity.Itconsiderssevenperspectivesontheuseoftimberinbuildingdesign,exploringwhereandwhenitisused,factorsinfluencingitsadoption,andhowitmightevolve.Thesesevenfactorsbestreflecttimber’scurrentsocial,technological,environmental,economicandpoliticalcontext,andprovideabroadandholisticreview: 1.Managingourcarbonbudget 2.Urbandensification 3.Woodandwell-being 4.Thefutureisprefabricated 5.Sustainablesourcing 6.Knowingthematerial 7.Innovatingwithwood Thereportisrelevanttothosewhoneedtotakealongviewofconstructionindustrytrends,andanyonewhohasastakeinthematerialswechoosetobuildwith,andtheimplicationsthesechoiceshavefortheenvironment,forspeedofprocess,forqualityofoutcome,andfortheamenityandsafety ofoccupants. Terminology Thisreportdescribesanewmethodofdesigningandconstructingmulti-storeytimberbuildings,variouslycalledmassivholz(German),masstimber,massivetimber,heavytimber,solidtimber,orengineeredtimber. Thetermusedinthisdocumentismasstimber.1Theperformancecharacteristicsofmasstimberaredifferenttothoseoftraditionalstudandjoistconstructioninjustabouteveryrespectsuchasstructural,fireresistance,buildingacoustics,physicsanddynamics. Glossary Brettstapel:methodofadhesive-andnail-freesoftwoodtimberconstructionusinghardwooddowelstojoincomponents. Cassettes:prefabricatedtimbercomponentsforuseinwallandroofassembly. CLT:cross-laminatedtimbercompriseslayersoftimberboards,alsoknownasdimensionallumber,arrangedperpendiculartooneanotherandgluedtogether,