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1、錨逆耢刃舯醴氨莛錳皿淘迓UseofVaporBarrierstoPreventCondensation誰束騁賞桷硪薛逵弟斟鵒預(yù)Wheneverinsulationisinstalledinawall,roof,orslab,itsresistancetotheflowofheatissomuchgreaterthanthatoftheotherelementsoftheconstructionthatthedewpointandresultingcondensationmayoccurwithintheinsulation.竽芤狂腱夫徹暹讕爆碴螗鉚
2、Sincewatervaporflowsfromregionsofhightemperaturetoregionsoflowtemperature,asimplesolutiontocondensationistostoptheflowofwatervaporbymeansofsomesurfacematerialimpervioustomoisture---providedthissurfaceiscalledavaporbarrier.Itmustalwaysbeappliedonthewarmside.癥希貢圍饅技湛墳浣媾橘免Becausec
3、ondensationisgenerallymostsevereduringtheheatingseason,allvaporbarriersshouldbeinstalledontheinteriorsideofwallsandroofs.Fromapracticalstandpoint,thismeansthatthevaporbarriershouldbenexttoandpartoftheinsulation.竄薯悚痞竅聳歌藻篌轂揀倡Oneofthebestandmosteconomicalvaporbarriersisaluminumfo
4、il.Someinsulationcomeequippedwiththisfoilattachedtoonesurface.However,unlessreinforcedwithkraftpaperorsomeotherstrongmaterial,thefoiliseasilyripped,torn,orpunctured,andsoisoflittlevalueasabarrier.嗲臾磨努齊涉隧捍漿酚艟蝶Sincevaporbehavesasagas,avaporbarrier,tobeeffective,mustbeairtight,or
5、asnearlysoaspossible.Butthisisoftenanimpracticalrequirement.Forexample,consideraroofwiththeinsulationabovethedeckandbetweenavaporbarrierandwaterproofroofing.Unlesstheinsulationisofafirmmaterial,theinsulationtoexpand,formingbubblesunderthewaterproofing.炻餅莞韭徨茁鉈紺杵湯襲繇Duringthecool
6、nessofthenight,thebubbleswillcontract.Afteraseriesofsunnydaysandcoolnights,thebendingbackandforthofthesurfacemaydestroytheroofing.Onewaytopreventthisistoside-venttheroofinsulationsothecontainedaircanfreelyexpandandcontract.Thesideventsmust,however,beprotectedfromdrivingrain.亞愀
7、澄懋汔跛玳騰著焊寰嵴Vaporbarrierscanbemadeofothermaterialsbesidesaluminumfoil.Therearealuminumpaints,plasticpaints,someplasticfilms,asphaltpaints,rubber-basepaints,asphalt,andfoil-laminatedpapers.Itmustberememberedthatwaterrepellentsurfacesarenotnecessarilyvaporbarriers,thatis,airtight.
8、朧傲苊謄鞴淅殮咦爿腸疳居Toevaluateavaporbarrier,aunitknownasthepermisused
