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ArchitectureinaClimateofChangePage52-Page62LowenergytechniquesforhousingItwouldappearthat,fortheindustrialisedcountries,thebestchanceofrescuelieswiththebuiltenvironmentbecausebuildingsinuseorinthecourseoferectionarethebiggestsingleindirectsourceofcarbonemissionsgeneratedbyburningfossilfuels,accountingforover50percentoftotalemissions.IfyouaddthetransportcostsgeneratedbybuildingstheUKgovernmentestimateis75percent.Itisthebuiltenvironmentwhichisthesectorthatcanmosteasilyaccommodatefairlyrapidchangewithoutpain.Infact,upgradingbuildings,especiallythelowerendofthehousingstock,createsaclusterofinterlockingvirtuouscircles.ConstructionsystemsHavingconsideredthechallengepresentedbyglobalwarmingandtheopportunitiestogeneratefossil-freeenergy,itisnowtimetoconsiderhowthedemandsideoftheenergyequationcanrespondtothatchallenge.Thebuiltenvironmentisthegreatestsectoralconsumerofenergyand,withinthatsector,housingisinpolepositionaccountingfor28percentofallUKcarbondioxide(CO2)emissions.IntheUKhousinghastraditionallybeenofmasonryandsincetheearly1920sthishaslargelybeenofcavityconstruction.Thepurposewastoensurethatasaturatedexternalleafwouldhavenophysicalcontactwiththeinnerleafapartfromwalltiesandthatwaterwouldbedischargedthroughweepholesatthedamp-proofcourselevel.Sincetheintroductionofthermalregulations,initiallydeemednecessarytoconserveenergyratherthantheplanet,ithasbeencommonpracticetointroduceinsulationintothecavity.Foralongtimeitwasmandatorytopreserveaspacewithinthecavityandalongrearguardbattlewasfoughtbythetraditionaliststopreservethis‘sacredspace’.DefeatwasfinallyconcededwhensomeextensiveresearchbytheBuildingResearchEstablishmentfoundthattherewasnogreaterriskofdamppenetrationwithfilledcavitiesandinfactdampthroughcondensationwasreduced.SolidmasonrywallswithexternalinsulationarecommonpracticeincontinentalEuropeandarebeginningtomakeanappearanceintheUK.InCornwallthePenwithHousingAssociationhasbuiltapartmentsofthisconstructionontheseafront,perhapsthemostchallengingofsituations.Theadvantagesofmasonryconstructionare:●Itisatriedandtestedtechnologyfamiliartohousebuildingcompaniesofallsizes.●Itisdurableandgenerallyriskfreeasregardscatastrophicfailure–thoughnotentirely.AfewyearsagotheentireouterleafofauniversitybuildinginPlymouthcollapsedduetothefactthatthewalltieshadcorroded.●Exposedbrickworkisalowmaintenancesystem;maintenancedemandsriseconsiderablyifitreceivesarenderedfinish.●Fromtheenergyefficiencypointofview,masonryhomeshavearelativelyhighthermalmasswhichisconsiderablyimprovediftherearehighdensitymasonryinternalwallsandconcretefloors.FramedconstructionVolumehousebuildersareincreasinglyresortingtotimber-framedconstructionwithabrickouterskin,makingthemappearidenticaltofullmasonryconstruction.Theattractionisthespeedoferectionespeciallywhenelementsarefabricatedoffsite.However,thereisanunfortunatehistorybehindthissystemduetoshortcomingsinqualitycontrol.Thiscanapplytotimberwhichhasnotbeenadequatelycuredorseasoned.Framedbuildingsneedtohaveavapourbarriertowallsaswellasroofs.Withtimberframingitisdifficulttoavoidpiercingthebarrier.Therecanalsobeproblemsachievinginternalfixings.Forthepurist,theultimatecriticismisthatitisillogicaltohaveaframedbuildingcladinmasonrywhenitcriesoutforapanel,boarded,slateortilehungexternalfinish.Pressedsteelframesforhomesarenowbeingvigorouslypromotedbythesteelindustry.Thesellingpointisagainspeedoferectionbutwiththeaddedbenefitofaguaranteedqualityintermsofstrengthanddurabilityofthematerial.Fromtheenergypointofview,framedbuildingscanaccommodatehighlevelsofinsulationbuthaverelativelypoorthermalmassunlessthisisprovidedbyfloorsandinternalwalls.InnovativetechniquesPermanentInsulationFormworkSystems(PIFS)arebeginningtomakeanappearanceinBritain.TheprinciplebehindPIFSistheuseofprecisionmouldedinterlockinghollowblocksmadefromaninsulationmaterial,usuallyexpandedpolystyrene.Theycanberapidlyassembledonsiteandthenfilledwithpumpgradeconcrete.Whentheconcretehassettheresultisahighlyinsulatedwallreadyfortheinstallationofservicesandinternalandexteriorfinishes.TheycanachieveaU-valueaslowas0.11W/m2K.Abovethreestoreystheadditionofsteelreinforcementisnecessary.Theadvantagesofthissystemare:●Designflexibility;almostanyplanshapeispossible.●Easeandspeedoferection;skillrequirementsaremodestwhichiswhyithasprovedpopularwiththeself-buildsector.Experiencederectorscanachieve5m2permanhourforerectionandplacementofconcrete.●Thefinishedproducthashighstructuralstrengthtogetherwithconsiderablethermalmassandhighinsulationvalue.SolardesignPassivesolardesignSincethesundriveseveryaspectoftheclimateitislogicaltodescribethetechniquesadoptedinbuildingstotakeadvantageofthisfactas‘solardesign’.Themostbasicresponseisreferredtoas‘passivesolardesign’.Inthiscasebuildingsaredesignedtotakefulladvantageofsolargainwithoutanyintermediateoperations.Accesstosolarradiationisdeterminedbyanumberofconditions:●thesun’spositionrelativetotheprincipalfacadesofthebuilding(solaraltitudeandazimuth);●siteorientationandslope;●existingobstructionsonthesite;●potentialforovershadowingfromo