Energy Efficient Windows in Multifamily Buildings%2c rev rt
1. Installing Energy Efficient Windows in Multifamily Buildings Cuts
Energy Consumption and Reduces Carbon Footprints
Most people livingin the UnitedStatesandeveryenvironmentalist knowswhata‘carbon
footprint’is.Simplyput,itisthe total amountof greenhouse gasesemittedintothe airdirectlyor
indirectlyfromsome person’sorentity’sactivities,usuallymeasuredin CO2emissions.Itisalsowidely
understoodthatusingelectricitydirectlycausesanincrease inCO2emissionsfromfossil-fuelusing
powerplants. Multifamilybuildingsmake upabout18% of our nation’shousingandthatnumberhas
beenincreasinginrecentyearsdue touncertaintyinthe real estate industry.Accordingtoananalysis
done byEnergy ProgramsConsortium85% of multifamilystructureswerebuiltbefore 1990 with
inefficientheating,cooling,plumbing,andlightingsystems.Thisunfortunate statisticisonlymade worse
by the fact that the majorityof familieslivinginmultifamilybuildingsare renterswithanannual income
of $31,000, and these lowerincome familiesthatneedenergysavings are forcedtopaymore forenergy
due to inefficacy. Thislowerstheirdiscretionaryincome andmakesthemmuch more vulnerableto
fluctuationsinenergyprices,whichare increasingata fasterrate thanhousingcosts;between2001 and
2009, rentersinmultifamilyunitsfacedanaverage rentincrease of 7.6 percent,while energycostsfor
these rentersrose by22.7 percent.
What can be done?
For multifamilybuildingsalreadybuiltandoccupied,itwouldbe unrealistic togo and replace all
the windowswithenergyefficientones.Atthispointinstallingthermostatstocontrol temperatures
duringtimesof lowenergyuse andusinglow-costtechniquesare the beststrategies forthese
apartments.Nevertheless,manynewmultifamilyhomesare
beingbuilttomeetthe demandfromcost conscious consumers.
For example,IntusWindowswereusedina48-unitmultifamily
projectinMaine that recentlywascompletedand now offers
tenantsa lease withouthavingtopayforheating,hotwater,or
sewage. Forprojectslike thisthe use of energy efficient
windowscansignificantlycutenergyconsumptionand
therefore reduce carbonemissions.Inthe past,structural,
safety,andsupportissueskeptarchitectsfromusingenergy
efficientwindowsincommercialmultifamilyprojects.They
were primarily usedinresidential homeconstruction.Howeverwithadvancesintechnology,companies
like Intusnowofferpolymerwindowswithframesreinforcedwithsteel u-channels thatcanstructurally
supportlarge commercial projects. These polymerwindow solutionscostonaverage the same as
genericaluminumwindowsthatbarelymeetcode requirementsformostnortherncities. Architectscan
implementIntuswindowsin theirnextprojectswithoutbreakingthe budget. Sonow thatenergy
efficientwindowsare beinginstalledincommercial projects, how muchenergyisbeingsavedcompared
to oldermultifamilystructures? We will take alookatthe numbers.
The numbers
To firstunderstandhowmuchenergyisbeingsavedbyenergyefficient windows.Itmustbe
understoodwhatsourcesconsume the mostamountof energywithinmultifamilybuildings.The graph
1: Multifamilybuilding in Maine featuring
Intus Windows
2. on the rightcreatedusingdata fromthe U.S EnergyInformation
Administrationshowsthatspace heating isthe biggestcontributorat
(41%) andcombinedwithairconditioning (8%),theymake upnearly
half of the energyconsumedinmultifamilybuildings. Toaccurately
compare efficientversusinefficientwindowswe mustknow how
inefficientolderbuilding’swindowsactuallyare.ThankstoRDH’s
research, a consultingfirmforarchitectsinCanada, the thermal
envelopeperformance of 13 representative buildingswasmodeledin
detail usingthe thermal simulationprogramsTHERM5.2 and WINDOW.Thisincludedhundredsof wall,
roof, and windowmodelsbasedonoriginal drawingswhile takingintoaccountactual construction
details,thermal bridging,andwindowanddoorsizesandframe configuration.Thisanalysisincludes
bothoriginal 1980s enclosure conditionsaswell asthe envelopesthathave beenrehabilitatedin recent
years. The windowsof multifamilystructuresbuiltinthe 1980s had a veryhighU-value of (0.75) and
those rehabilitatedbuilding’sU-valuesrangedfromwindowswithlow E-value(0.45) andthose with
clear-glasswindows(0.6).Still notveryimpressive.RDHBuildingEngineersdrafteda digital ‘study
building’ withcomputerprogramsandfound thata thermallyimprovedenclosure designwithU-0.17
windows,walls withaneffective R-valueof about18, airtight
constructionand80% heatrecoveryonventilationaircanresultin 50%
to 90% heating energy use reductions as comparedtotypical current
high-rise residentialbuildings. Assumingwe have metthe R-value of 18
and are usinga HRV/ERV ventilationsystem;Intustriple-panedtriple-
glazedwindowsprovide aU-Value rangingfrom0.15-0.17, and <.01
cfm/ft2air tightness. IntusWindowsmeetsthe standardssetbythe
RDH studyfor reducing50%-90% of heatingenergy use.Thereforeitcan
be recognized thatinstallingIntuswindows innew multifamilybuildings
can reduce space heatingdown from41% of total energyconsumption
to only 6.5% of total energy consumption usedforspace heatingin
multifamilybuildingscomparedtoperformancesof the sample 13
representative buildings.Thisisa hefty reductioninenergy use that
logically translatestoa reductioninthe carbonfootprintforeverysingle man,woman,andchildlivingin
that multifamilybuilding. Take forexample acase studydone bythe USGBS on The Solaire multifamily
buildinginNewYorkCity.The average unitconsumed15,681 kBtu of energyperyear andreleased3690
poundsof carbon dioxide intothe atmosphere throughthisconsumption.If all the standardsoutlinedby
the RDH were metandthe buildingwasusingIntusWindows,eachunitwouldhave onlyconsumed
9,252 kBtuof energyandreleased2,177 poundsof carbon dioxide intothe atmosphere justfromheat
energyuse diminutions.Thatisa reductionof 1,513 poundsof carbon dioxide releasedintothe airper
unitina buildingwith293separate units. Architectsmustacknowledge thatmultifamilybuildingswillbe
occupiedbyfamiliessusceptible toenergyprice fluctuations.Itisthe corporate social responsibility of
the building’s ownerstoprovide the mostenergyefficientunitstheycanpossibly afford.Itnotonly
benefitsthe familiesthatwill live intheseapartmentsandcondos,butitbenefitsthe environmentasa
whole. Thisconceptmaysound toogood to be true,but thistechnologyhasthe potential tochange the
world.IntusWindowswantsclientstoknow thatchoosingourwindowsmeansmore thanjustsavings
and style;itmeansthe reductionof your building’s energyuse,reductioninthe carbonfootprintsof
your tenants, andthe preservationof the Earthwe call home.
