RobinLancashireandLewisTaylor Innovative timberconstruction Newwaystoachieveenergyefficiency
innovativetimber construction
RobinLancashireandLewisTaylor
innovativetimberconstruction
Asthermalperformancerequirementshavebecomeharderandmore expensivetoachieve,allsectorsoftheconstructionindustryneedto considerbuildingathickerexternalenvelopetoprovidespaceforinsulation. Thisneedisonlygoingtoincreaseastheindustrymovestowardthe‘Zero Carbon’targetin2016.Fortimberframeconstruction,merelyincreasing thedepthofsolidtimberstudsandfittingmoreinsulationbetweenthemis becominginsufficienttomeettheincreasingrequirementsforthermaland energyperformance.
Althoughenthusiastshavedesignedavarietyoflow-energytimberframe buildingsoverrecentdecades,thetechniquesusedhaveremainedon theperipheryoftheconstructionindustry,withmainstreamtimberframe evolvingslowlytokeeppacewithnationalbuildingregulationchanges.This bookhasbeenwrittentoexpandoninformationprovidedonsomealternativeformsoftimberconstructionmentionedin
Fourofthemostcommontypesofalternativetimberwallsandroofsare exploredhere.Thesearestructuralinsulatedpanels(SIPs),cross-laminated timber(crosslam),engineeredstudandtwinstud.
RobinLancashireisheadoftheBuildingPerformancesectionatBM TRADAwithparticularexpertiseintimberframeconstruction.
LewisTaylorisatimberframeconsultantatBMTRADAwithparticular expertiseinthermalandacousticperformance.
3
5 1Introduction7 1.1Designrequirements7 1.5Airpermeability11 1.6Walls11 2SIPs13 2.1Applications13 2.2Sustainability14 2.3Structure14 2.5Erection15 2.7Airtightness20 2.9Services22 3Engineeredstud23 3.1Applications23 3.2Sustainability24 3.3Structure24 3.5Erection25 3.7Airtightness27 3.9Services31 4Cross-laminatedtimber33 4.1Applications33 4.2Sustainability34 4.3Structural34 4.5Erection37 4.8Airtightness40 4.9Services41
Innovativetimberconstruction 6 5Twinstudwalls43 5.1Applications44 5.2Sustainability44 5.3Structural44 5.5Erection46 5.7Airtightnessandcondensation48 5.8Services50 6Lookingahead51 References53 Furtherreading53
1Introduction
Asthermalperformancerequirementshavebecomeharderandmore expensivetoachieve,allsectorsoftheconstructionindustryhavebeen drivendownthepathofbuildingathickerexternalenvelopetoprovide spaceforinsulation.Fortimberframeconstructionithasnowreacheda stagewhenmerelyincreasingthedepthofsolidtimberstudsandfitting moreinsulationbetweenthemisbecominginsufficient.Tokeepuptodate withcurrentthermalperformanceregulations,thedetailsin 1haveintroducedaninsulatedservicezoneonthe insideofthewalltohelpimproveairtightnessandallowspaceformoreinsulationtobeinstalled.Dependingontheinsulationmaterialsused,U-values below0.2W/m2Kcanbeachieved.
predominantlydealswithwhatcouldbeconsidered‘conventional’platformtimberframeconstruction–thepanelisedform ofconstructionusingsolidtimberwallstudsandrailswithwood-based sheathingboards.ThismethodhasbeenembracedbytheUKconstruction industryasastandardformoftimberframeconstructionoverthelast50years.
Althoughenthusiastshavedesignedavarietyoflow-energytimberframe buildingsoverrecentdecades,thetechniquesusedhaveremainedon theperipheryoftheconstructionindustry,withmainstreamtimberframe evolvingslowlytokeeppacewithnationalbuildingregulationchanges. DrivenbytheneedtoreduceCO2emissions,theEuropeanUnionhasstarted tosetever-tighterrequirementsontheenergyperformanceofbuildings, leadingto‘zero-carbon’buildingsby2016.
Thisbookhasbeenwrittentoexpandoninformationprovidedonalternative formsoftimberconstructionmentionedin .Four ofthemostcommontypesofalternativetimberwallsandroofsareexplored here.Thesearestructuralinsulatedpanels(SIPs),cross-laminatedtimber (crosslam),engineeredstudandtwinstud.Althoughthesesystemsareall different,theystillfollowthebasicprinciplesoftimberframeconstruction thataresetoutin .Althoughthisbookhasbeen writtenasastandalonepublication,itisnotintendedtobeafulltechnical manualforeachconstructiontype,butdemonstrateswhatispossibleandhow eachoftheformsworksinprincipletoprovideaneffectivethermalenvelope.
Moreindustrychangeswillbeneededtomeet2016regulations.Inorderto achievefurtherreductionsinU-valuesandachievebuildingswithminimal energyrequirements,timberframedesignersandarchitectsarebeginningto exploresomeofthesealternativetypesoftimberframeconstruction,which havebeenontheperipheryformanyyearsbutarenowbecomingbetter appreciatedfortheirhighlevelsofthermalperformance.
1.1Designrequirements
Timberframebuildingshavedemonstratedthattheyareadurableformof constructionandcaneasilyachieveaminimumdesignlifeof60years.There aremanyexamplesofsoftwoodtimberframebuildingsthatarehundreds ofyearsold.Inaddition,timberframebuildingshaveevolvedtoprovide goodthermalandacousticperformance.Itisimportanttoremember,when makingfurtherimprovementsinthermalperformance,tomaintainthesame gooddesignprinciples.
7
2SIPs
Astructuralinsulatedpanel(SIP)consistsofalayeroforientedstrand board(OSB)bondedontoeachsideofaninsulatingfoamcore.Astrong, structuralbondbetweenthethreelayersisessentialtotheloadbearing abilityoftheSIP.TheresultantsandwichofOSBandfoamcanbeusedas astructuralloadbearingelement.ASIPisacompositeengineeredproduct, witheachbuildingbeingindividuallydesignedandengineered.SIPstructurescanoffergoodthermalandairtightnessperformancewithminimal thermalbridgingduetothecontinuousnatureoftheinsulationcorewithin thepanel.
SIPbuildingswerefirstresearchedinNorthAmericainthe1930sand40s. SIPsasweknowthemtodaywereconceivedinthe1970sandhavebeenin usesincethen.
2.1Applications
SIPsareusedforexternalwallandroofstructureswheregoodthermal performancewithminimalthermalbridgingisdesired.Currently,loadbearingSIPstructuresaregenerallylimitedtofourstoreysinheightfor structuralreasons.AsSIPstructuresbecomelargerormorecomplex,additionalelementsofstructuremayberequiredtosupporttheimposedloads; however,theseelementsofstructurewillreducethethermalperformance benefitsoftheSIP.SIPscanalsobeusedasin-fillpanelsonlargemulti-storey steel-orconcrete-framedbuildings.Large-formatSIPscanbecranedinto placeandfixedtotheoutsideoftheframe,providingrapidenclosureofthe structurewiththermalinsulationalreadybuiltintothewalls.SIPwallscan becladwithalltypicalcladdingmaterials,suchasmasonry,timberorother lightweightsystems.
13
Figure2.1Joiningpanels
5Twinstudwalls
Atwinstudwallisasimple,easymethodofgettingalotofinsulationinto awallwithrelativelyinexpensivematerials.Itissimplytwotimberframe studwallsinparallel,separatedbyacavity,butonlyoneofthesecarriesthe verticalloadofthebuilding.Dependingonthestructuraldesignandorder ofworkproposedonsite,thiscanbeeithertheinnerortheouterwall.The cavitywidthandthedepthofbothwallstudscanbevaried,toprovidesufficienttimberforstructuralperformanceandspaceforinsulation.Thissimple methodusesmanymaterialsandtechniquesfamiliartothosewhobuild standardtimberframebuildings.
Toavoidrepetition,theillustrationswithinthischaptershowinternalloadbearingstuds,ablownfibreinsulationmaterialandtheinternalsheathing boardprovidingrackingresistance.Alternativedetailsmayshowexternal loadbearingstudsandsheathing,orquilt/batt/boardinsulationinany
43
Figure5.1Twinstudisometric
Innovativetimberconstruction
