byPaulTesta
W
henit cametotheexistingroofofthe
house,wehavebeenverypragmaticand
replacedthecoveringwithnewconcrete
tilestomatchtheoriginalandourneighbour,
butina crispergreytone.Weinsulatedtheroof
extensivelybetweenandbeneaththeraftersto
createa warmroofstructure.(Insulationis oneof
thekeyingredientstohelpingusachieveEnerPHit
standard—thePassivhausequivalentforexisting
homes.)Thismethodisn’tasefficientasceilinglevel
insulationbutenabledustodesigna vaultedspace
abovethestairswhichfeaturestwolargeFakrotriple-
glazedelectricrooflightsforsummerventilation.
Allofourroofingandtiledcladdinghasbeen
expertlyinstalledbyEssentialRoofCoverings.Their
adviceonthebestapproachtotheglassreinforced
plastic(GRP),rooffalls,drainageandsoonwhen
constructingtheflatroofforthesingle-storey
extension,hasbeeninvaluable;it’sonereasonwhy
it’sa goodideatoemploythebesttradesyoucan.Choosinga windowsupplier
Aftera numberofyearsworkingwiththem,
choosingGreenBuildingStoreasourwindow
supplierwasa relativelyeasydecision.It’sdifficultto
findanequalintermsofthebalancebetweencost,
performanceandservice.
Atthetimeofspecificationtheyonlysupplied
timberwindowsanddoors,andwechosetheir
cheapest‘performance’rangeoftriple-glazed
windows;thisis theonlyoneofthethreeranges
offeredthatdoesn’tcomewitha Passivhauscertified
option.Althoughtheyarecheaperthantheirother
products,thewindowsstilloutperformmoston
themarketandareadequateforPassivhausand
EnerPHitprojectsaslongasit is detailedcarefully.
Wewantedtomakesurethedetailingand
installationofthewindowsanddoorswereas
thermallyeffectiveaspossiblebutalsoeasily
achievableonsite.We’vetakena differentapproach
ontheexistinghouseandtheextension.Ontheexistinghouse,theinternalinsulationhasbeen
wrappedaroundthewindowrevealstogivethermal
continuityanda goodoverlapbetweenthewindow
andinsulation.Thereplacementwindowsareall
outwardopeningsothattheoverlapontheinside
canbeasbigaspossiblewithoutinterferingwiththe
openingcasements,andtheprimaryprotectionis an
outermasticseal.
Wehaveinstalledtheextensionwindowstothe
outeredgeofthetimberframeandthenoverlapped
theexternalinsulationlayerovertheexternalfaceof
thewindowframes;thismeansthatthewindowsand
doorsoftheextensionareinwardopening.
Togivetheverybestweatherprotectionat the
edgesofthewindowstherearetwolayersofedge
sealingoneachinstallationandthere’ssecondary
protectionprovidedbyanexpandingfoamstrip
betweenthewindowandstructure.
Thedoorsandwindowshavea qualityfeeland
it’sgratifyingtoseecondensationontheoutsideof
theglassaftera coldnight—it’ssomethingyouonly
getwitha highperformancewindow.Paulchooses roof and glazing suppliers for his EnerPHit
remodelof a 1960s semi-detached house in Sheffield
flatroofing
thenewlybuiltflatroof
andterrace(above)
areconstructedwith
a structuraloSBdeck,
a thicklayerofrigid
insulationanda glass
reinforcedplastic
(grP) roof covering.Choosing our windows
was an easy decision
homebuilding.co.uk 209PaulteSta
is thedirector
ofPaultesta
architecture
and has a
special interest
in sustainable
designthe Build the eco retrofit diary