LEAKAGE REDUCTIONS FOR LARGE BUILDING AIR SEALING AND HVAC SYSTEM PRESSURE EFFECTS

Transcription

1 LEAKAGE REDUCTIONS FOR LARGE BUILDING AIR SEALING AND HVAC SYSTEM PRESSURE EFFECTS David Bohac *, Martha Hwtt, Jams Fitzgrald, Joshua Novachck, and Andrw Lutz Cntr for Enrgy and Environmnt 212 Third Avnu North, Suit 56 Minnapolis, MN, USA *Corrsponding author: ABSTRACT Building air lakag tsts wr conductd on six commrcial and institutional buildings bfor and aftr air saling work. Th tst protocol gnrally followd th rquirmnts of ASTM E779, with additions to addrss th complxitis of tsting largr buildings. Th buildings wr on to thr storis and wr constructd btwn 1936 and 27, with floor aras that rangd from 27, to 246, ft 2 (2,5 to 22,9 m 2 ). Bfor air saling, th buildings wr rlativly tight with normalizd air lakags that rangd from.15 to.31 cfm@75pa/ft 2 (2.6 to 5.7 m 3 /h m 2 ) using abov grad nvlop ara and.9 to.19 cfm@75pa/ft 2 including blow grad walls and slab. Th air saling focusd on cost ffctiv spray foam saling of th wall/roof joints, with upgrads of xtrior door wathrstripping a scond priority. Th saling rducd air lakag from 6 to 18% with a mdian of 11%. For thr of th buildings, th air saling contractor gnratd th work scop and stimatd th physical lakag ara to b sald. Th contractor stimatd air saling was significantly gratr than th masurd valus. Th ratio of masurd chang in th EqLA to stimatd sald ara rangd from.5 to.31. Thr was a consistnt and significant bias for highr lakag undr prssurization than dprssurization. Th ratio of prssurization to dprssurization tightnss for th pr and post saling masurmnts varid from 1.12 to 1.31 with a man valu of Individual door tsts indicatd that doors with loos latchs bing pushd opn during prssurization may hav bn rsponsibl for about 17% of th incrasd lakag for prssurization at on of th schools. Th air tightnss tsts wr conductd with xhaust fans, outdoor air inlts, and xhaust air outlts tmporarily sald. Singl point tsts wr conductd aftr th sals wr rmovd to comput mchanical systm lakag. Th normalizd lakag rangd from.19 to.137 cfm@75pa/ft 2 and incrasd th nvlop lakag by 15% to 119%. This suggsts that mchanical systm air lakag can hav a significant ffct on building air lakag whn th systms ar off. Air saling contractors oftn stimat nrgy savings from monthly avrag wind prssur or wind and stack prssur ls that do not includ hating, vntilation, and air conditioning (HVAC) ffcts. Long-trm building prssur monitoring indicatd that HVAC opration positivly prssurizd many of th buildings. For on of th buildings th prssur at roof lvl was typically abov +4Pa whn th outsid tmpratur was lowr than 4F. In thos situations ignoring th HVAC prssur ffct rsults in high stimats of air infiltration and air saling nrgy savings. Howvr, thr wr also tims whn th HVAC systm causd dprssurization and in thos situations infiltration and air saling savings would b undrstimatd. KEYWORDS Airtightnss, infiltration, commrcial buildings, mchanical systm lakag, HVAC prssur ffct.

2 1. INTRODUCTION Building architcts, nginrs, contractors, and facility managrs tnd to think of larg buildings as fairly airtight and assum that nvlop air lakag dos not typically hav a significant impact on nrgy us in commrcial and institutional (C&I) buildings (Prsily, 1988). Emmrich (25) conductd lling that contradicts that convntional wisdom, stimating that infiltration accounts for 33% of total hating nrgy us in U.S. offic buildings. Svral stats, including Minnsota, hav rcntly incorporatd air barrir rquirmnts into thir nrgy cods for nw C&I buildings. In addition, th US Army Corps of Enginrs (USACE) has stablishd a prformanc airtightnss rquirmnt for nw buildings and major rtrofits of.25 cfm/ft 2 (1.25 L/s m 2 ) of total nclosur surfac ara at a prssur of 75 Pascals (USACE, 21); and othr cods or organizations hav adoptd a standard of.4 cfm/ft 2 (2. L/s m 2 ). Howvr, th building stock that xistd prior to this incrasd mphasis on nvlop tightnss contributs much mor to ovrall nrgy us than do buildings built sinc ths changs, and will continu to for many yars, as th C&I building stock turns ovr slowly. Rducing air lakag nrgy us in xisting buildings rquirs ffctiv scrning tools to idntify buildings with a highr probability of having tratabl laks; invstigation mthods to idntify ky nvlop air lakag dficincis and/or mchanical systm prssur issus; and rliabl procdurs to stimat cost and savings. This projct was initiatd to dvlop and tst nvlop air lakag scrning protocols, invstigation protocols, masur th chang in building lakag du to air saling, l th ffct of lakag rduction on spac conditioning loads, and gnrat cost and savings stimation procdurs. Projct staff conductd air lakag invstigations on 25 xisting C&I buildings, including whol building air lakag tsts bfor and aftr air saling on six of thos buildings. Thy also rcordd continuous building indoor to outdoor prssur and mrgd it with automation systm trnd data to valuat th ffct of th hating, vntilation, and air conditioning (HVAC) systm on building prssur. Thos rsults ar bing usd to dvlop CONTAM ls (Walton, 213) that includ HVAC prssur ffcts. This papr prsnts th rsults of th air lakag tsts and continuous prssur monitoring. 2. METHODOLOGY Th building air tightnss tsts gnrally followd th rquirmnts of ASTM E779-1 (21), with additions to addrss th complxitis of tsting largr buildings. Th ky additions to or clarifications of th tst protocol ar outlind blow: In/outdoor prssur snsors. Th avrag of four ground lvl in/outdoor prssur masurmnts placd on diffrnt sids of th building was usd to indicat th building indoor with rspct to outdoor prssur diffrnc. Baslin prssurs. Building baslin prssurs wr masurd for at last fiv minuts bfor and aftr both th prssurization and dprssurization tsts. Tst prssurs. Multipl, calibratd fans wr usd to vary th baslin adjustd building in/outdoor prssur at 5Pa incrmnts from approximatly 15 to 75Pa. Masurmnts wr conductd at 13 to 16 prssur lvls for 6 sconds at ach lvl. Mchanical systms. All mchanical damprs wr closd and th damprs or trminations of th outsid air ducts, xhaust air ducts, and xhaust fans wr tmporarily sald. Aftr th dprssurization tst was compltd, th tmporary sals wr rmovd squntially from th mchanical quipmnt whil th tst fans wr

3 usd to dprssuriz th building to a baslin adjustd prssur of approximatly - 75Pa. On minut of masurmnts wr rcordd at ach stag of th unsaling. Th masurd fan flow rat and building prssur wr usd with th dprssurization tst baslin and flow xponnt to comput a total building lakag for a rfrnc prssur of 75Pa. Th nvlop only building lakag was subtractd from that valu to dtrmin th additional lakag du to th mchanical systms. Projct staff usd commrcially availabl softwar to rcord building prssur diffrncs, rcord fan flow rats, control tst fan spds, graphically display th masurmnts, and comput air lakag valus. Thy improvd data quality by using distributd gaugs to minimiz tub lngths and ral-tim rgrssion analysis to idntify rronous masurmnts. Exprincd staff or consultants conductd th building air lakag invstigations with a combination of an xtrior infrard (IR) survy and intrior lak invstigation with smok visualization. Thy usd th building s HVAC systm or tmporary fans to prssuriz th buildings for th xtrior survys (ASTM E1186-3, 29); and conductd th invstigations with a minimum insid to outsid tmpratur diffrnc of 18F, with no dirct solar radiation on th surfacs for four to six hours prior to th survy. Th rsults of th IR survy and xprinc of typical lakag sits hlpd guid a visual nvlop lakag invstigation. From th building intrior a smok puffr was usd to rlas chmical smok nar suspctd lakag sits. Th vlocity and volum of smok movmnt indicatd th rlativ magnitud of air lakag. Th invstigations typically focusd on wall/roof intrsctions, roof lvation changs, xtrior doors, mchanical systm pntrations, and windows. Th final stp in th procss was to dtrmin cod compliant mthods for saling th major nvlop air laks. Staff consultd building wall and roof air barrir dtails whn availabl; and only considrd saling that rquird limitd or no rmoval of building matrials. Air saling contractors oftn stimat nrgy savings from monthly avrag wind prssur or wind and stack prssur ls. Th ls do not typically includ th ffcts of mchanical systm opration on th building prssur. Prssur monitors wr installd at th buildings to rcord on minut avrags of building insid with rspct to outsid prssur diffrncs at on to thr intrior locations. Th tubs for th outdoor prssur rfrnc xitd th buildings at ithr th roof or ground lvl dpnding on accssibility. Th monitoring priods lastd 5 to 2 days. Th prssur data was convrtd to 15 minut avrags and mrgd with local wathr station outdoor tmpratur, wind spd, and wind dirction data. Building automation systm trnd data was usd to idntify and un opration s. Th data has bn analyzd to valuat th ffct of HVAC opration on th variation in building prssur with outsid tmpratur. Th nxt phas of th projct is dvloping CONTAM ls (Walton, 213) using th building air lakag tst data to stablish th sum of th nvlop and mchanical systm lakag. Th un data will dtrmin th building s nutral lvl to assist with assigning th vrtical distribution of CONTAM nvlop air lakag. Finally, analysis of th prssur and HVAC trnd data will stablish th variation with outsid tmpratur in building prssur inducd by th HVAC supply and xhaust systm flow rats.

4 3. RESULTS AND DISCUSSION 3.1. Pr-Saling Building Tightnss Th projct conductd air saling and lakag tsts on two lmntary schools, a middl school, a univrsity library, a combination community library/offic, and a small offic building. Th building IDs shown in Tabl 1 indicat th building typ. Th buildings wr on to thr storis tall built from 1936 to 27, with floor aras ranging from 26,927 to 246,365 ft 2 (about 2,5 to 22,9 m 2 ). Th pr-saling building air tightnss normalizd by th abov grad nvlop ara (i.. fiv sids) rangd from.15 to.31 cfm/ft 2 (2.6 to 5.7 m 3 /h m 2 ) and.9 to.19 cfm/ft 2 whn normalizd by th six sids ara that includs blow grad walls and slab (s Tabl 1). Both sts of valus us a rfrnc prssur of 75Pa. Tabl 1: Building charactristics and pr-saling air tightnss Air Lakag at 75Pa Floor Envlop Ara (ft 2 ) 5 Sids 6 Sids # Constr Building ID Ara (sf) 5 Sids 1 6 Sids 2 (cfm) (cfm/ft 2 ) (m 3 /h. m 2) (cfm/ft 2 ) Storis Yar Wall Typ Elm School TF 59,558 87, ,977 27, Masonry & corrugatd mtal panl Middl School 138,887 13,318 28,733 32, Cast concrt w/cmu infill Small Offic 26,927 38,34 65,267 9, EFIS tip up (3 walls) and CMU block Univ Library 246,365 98,24 171,712 23, Cast concrt w/cmu infill & brick xt Elm School PS 6,968 84, ,766 17, CMU w/brick xtrior Library/Offic 55,47 84, ,965 12, Stl studs & brick or ston cladding Minimum 26,927 38,34 65,267 9, Man 98,19 87, ,43 2, Mdian 6,263 86,18 146,371 2, Maximum 246,365 13,318 28,733 32, abov grad surfac ara 2 includs blow grad xtrior walls and slab Th buildings wr much tightr than xpctd, vn though many of th buildings wr oldr and non wr rquird to mt a tightnss standard at th tim of construction. Th avrag normalizd tightnss of.23 cfm/ft 2 (4.2 m 3 /h m 2 ) was 83% lss than th avrag valu of 1.38 cfm/ft 2 rportd by Emmrich (211) for a convninc sampl of 227 U.S. C&I buildings. Th tightnss of th lakist of th six buildings was lss than th 25 th prcntil of Emmrich s databas and was 25% tightr than th USACE standard. It is possibl that buildings in cold climats ar tightr du to gratr concrn for cold drafts, frozn pips, and highr spac hating costs. A prvious analysis by Emmrich (25) suggstd that buildings in coldr climats ar gnrally tightr than th U.S. avrag. Th rsults for ths six buildings ar consistnt with that trnd, but a largr sampl is ncssary to proprly dtrmin th distribution of normalizd lakag and th fraction of nw buildings that would b impactd by a lakag standard or xisting buildings that ar likly to hav cost ffctiv air saling opportunitis Air Saling Lakag Rduction Th air saling focusd on cost ffctiv spray foam saling of th wall/roof joints, with upgrads of xtrior door wathrstripping a scond priority, and mchanical systm pntration saling was compltd at som of th buildings. An air saling contractor conductd th initial invstigations of th thr school buildings. Projct staff conductd follow-up invstigations and th contractor adjustd th work scop basd on staff fdback. Th contractor s proposals includd stimats of lakag ara to b sald and nrgy savings. For th thr lmntary and middl schools th contractor stimatd that 81% of th saling would b producd from wall/roof joint foam saling and 15% from xtrior door

5 wathrstripping. Saling stimats wr not stablishd for th othr thr buildings. For two of th buildings (Univ. Library and Library/Offic) th work only includd wall/roof saling. Th rooftop unit pntrations and CMU bam wall pockts nar th roof wr sald for about a quartr of th Small Offic building. Th air saling of th thr schools was compltd at th bid pric by th commrcial contractor who spcifid th work. A diffrnt commrcial contractor conductd th air saling at th Univ. Library and Small Offic sits on a tim and matrials basis. Projct staff compltd th limitd saling at th Library/Offic building and costs wr stimatd basd on th scond contractors tim and matrials rats. Post saling IR scans and smok puffr/visual invstigations wr compltd to confirm that spcifid air lakag was sald. All of th work was dtrmind to b succssful xcpt som of th wall/roof saling at th Univ. Library building which rquird additional xtrior saling that could not b compltd prior to th post tst schduld dat. Th masurd chang in building tightnss was smallr than xpctd. Th rduction in lakag at 75Pa (CFM75) rangd from 6% to 17% with a man of 1% (s Tabl 2). Th building with th highst normalizd lakag had th gratst rlativ rduction in lakag and thr was somwhat of a trnd of gratr rductions for th lakir buildings. In addition, th air saling cost pr CFM75 rduction incrasd for tightr buildings xcpt for th Library/Offic building whr thr was an isolatd, significant wall/roof lak that was inxpnsiv to sal. Th rsults suggst that it is possibl to rduc th lakag of vn tight buildings. Howvr, th saling potntial is bttr for lakir buildings unlss concntratd laks can b idntifid that ar inxpnsiv to sal. Sinc fw U.S. air saling contractors conduct air lakag tsts, thy must rly on smok puffr/visual lakag invstigations to idntify cost ffctiv air saling opportunitis. Tabl 2: Envlop air saling rsults Air Lakag at 75Pa Lakag Ara Sald Ara (sf) (cfm) Rduction EqLA (ft 2 ) Rduction Air Saling Cost Contractor Estimatd Building ID Pr Post (cfm) (%) Pr Post (ft 2 ) (%) Total ($/CFM75) ($/ft 2 ) Roof/Wall Total Mas/Est Elm School TF 27,425 22,699 4,726 17% % $ 18,55 $ 3.92 $ 6, Middl School 32,818 28,872 3,947 12% % $ 23,7 $ 6. $ 8, Small Offic 9,177 8, % % $ 4,768 $ 6.73 $ 1,58 Univ Library 23,356 21,963 1,392 6% % $ 15,918 $ $ 65,159 Elm School PS 17,62 15,837 1,765 1% % $ 26,7 $ $ 38, Library/Offic 12,321 11, % % $ 1,152 $ 1.21 $ 1,297 Minimum 9,177 8, % % $ 1,152 $ 1.21 $ 1,297 Man 2,45 18,21 2,249 1% % $ 15,131 $ 7.41 $ 21,65 Mdian 2,479 18,9 1,579 9% % $ 17,234 $ 6.37 $ 9,246 Maximum 32,818 28,872 4,726 17% % $ 26,7 $ $ 65,159 1 at 1 Pa rfrnc prssur for orific with a discharg cofficint of.61 All lakag valus ar avrag of prssurization and dprssurization tsts Th contractor stimatd air saling was significantly gratr than th masurd valus. Th actual lakag sald was stimatd from th diffrnc in th pr to post quivalnt lakag ara (EqLA). Th ratio of masurd chang in th EqLA to stimatd sald ara was.24 and.31 for th two lakir buildings, but only.5 for th scond to tightst building. For that building th contractor stimatd ara to b sald was gratr than th total lakag. Sinc th post saling inspctions showd littl or no lakag at th aras sald, it appars that th rason for th high sald ara stimats was an inability to proprly stimat physical lakag aras and not poor air saling tchniqus. Whil judging th vlocity of smok movmnt into a gap and th siz of th gap usd to stimat th siz of laks, that mthod is only qualitativ. Th width of a visibl gap at a joint will ovrstimat th quivalnt width of th air lakag path whn thr ar gratr rstrictions downstram in th

6 path. For xampl, th visibl lak ara for th gaps sald at th Library/Offic building was 3.3 ft 2 but th masurd chang in th EqLA was.9 ft 2 whn th ara was sald. Finally, whil it is possibl to us this mthod to stimat th flow rat of air moving into a lak, th prssur across th lak would nd to b known to accuratly quantify th quivalnt lakag ara. This limitd sampl suggsts that furthr work is rquird to dvlop mthods to mor accuratly dtrmin physical lakag ara Prssurization and Dprssurization Comparison Thr was a consistnt and significant bias for highr lakag undr prssurization than dprssurization. Th ratio of prssurization to dprssurization tightnss for th pr and post saling masurmnts for th six buildings varid from 1.12 to 1.31 with a man valu of 1.22 (s top row of Figur 1). This indicats that thr ar portions of th building nvlop that ar significantly lakir undr prssurization than dprssurization. This could b du to mmbrans that ar pulld tight to a surfac undr dprssurization or othr flappr situations. Projct staff noticd that th school buildings had a numbr of loos door latchs that allowd th doors to push opn during highr prssurs of th prssurization tst (typically abov 25Pa). Prssurization and dprssurization tsts wr conductd on 17 doors at thr of th school buildings. Figur 2 displays th rsults for on of th doors with loos latch movmnt. For 65% of th 17 doors, th prssurization CFM75 was ovr 4% gratr than that for dprssurization, and th avrag lakag diffrnc was 18 CFM75. If that avrag diffrnc is applid to th 26 xtrior doors for Elm School TF, th lakag diffrnc of 458 CFM75 would qual 17% of th 2,667 CFM75 highr lakag undr prssurization for th ntir building. Th door movmnt du to loos latchs provids on xampl of additional prssurization lakag. It is xpctd that thr ar svral additional situations that ar not as asy to obsrv or quantify. This raiss th issu of whthr a singl tst or an avrag bst rprsnts th building lakag undr typical opration, and which should b usd for building tightnss complianc standards /sf) 5 7 M F (C.15 g a k a L ir A.1 d liz a r m o N.5 Prssurization Dprssurization Prssurization/Dprssurization % (2%) 11% (2%) 14% (2%) 7% (2%) 5% (2%) 13% (2%) 8% (1%) 7% (3%) 1% (3%) 1% (2%) 6% (3%) 1% (3%). Pr Post Pr Post Pr Post Pr Post Pr Post Pr Post Elm School TF 1951 Middl School 1936 Small Offic 1998 Univ Library 1967 Elm School PS 1965 Library/ Offic 27 Figur 1: Building normalizd nvlop lakag pr and post air saling

7 ) 1.4, c fm t 1.3 a R w1.2 lo (F g o L1..9 Highr lakag whn buildingprssur "pushs" th door opn (35-45Pa) and latch is loos Tstr physically pushd door closd Log1(Envlop Prssur, Pa) Prssurization Dprssurization Prssurization, Highr Prss Figur 2: Prssurization and dprssurization lakag tsts on a door with a loos latch Th diffrnc in th prssurization and dprssurization tightnss also prsnts a concrn for valuating th ffct of air saling. Figur 1 displays th pr and post prssurization and dprssurization normalizd lakag. Th prcnt chang is shown to th right of th post masurmnt and th 95 th confidnc intrval uncrtainty is includd in parnthsis. For fiv of th six buildings, th diffrnc btwn prcnt chang in tightnss computd from th prssurization and dprssurization tsts is lss than th sum of th uncrtaintis. This indicats that ach tst mthod provids similar rlativ changs in tightnss, so ithr could b usd to valuat th ffct of air saling. Thr was oftn a significant diffrnc in th prssurization and dprssurization powr law quation xponnt. Figur 3 displays th xponnts from th pr and post tsts with th rror bars rprsnting th 95 th prcntil confidnc intrvals. Th prssurization xponnt was gratr than that for dprssurization for 1 of th 12 tsts, and for 7 of thos th diffrnc was gratr than th sum of th uncrtaintis..85 Prssurization Dprssurization.8.75 t n n o.7 p x E Pr Post Pr Post Pr Post Pr Post Pr Post Pr Post Elm School TF 1951 Middl School 1936 Small Offic 1998 Univ Library 1967 Elm School PS 1965 Library/ Offic 27 Figur 3: Powr law flow quation xponnt pr and post air saling 3.4. Mchanical Systm Lakag Whn th mchanical systms ar oprating and th outsid/xhaust air damprs ar opnd to rgulat air flow, th dampr lakag is typically not a concrn. Howvr, whn th systms

8 ar off, th damprs bcom part of th building s air barrir and dampr lakag causs additional building air infiltration or xfiltration. Dampr lakag poss a gratr concrn for buildings with a highr fraction of tim whn th mchanical systms ar off. Th mchanical systm lakag varid from 1,618 to 23,516 CFM75 and th six sids normalizd lakag varid from.19 to.137 cfm/ft 2 with a man of.47 cfm/ft 2 (s Figur 4). For thr of th buildings, th mchanical systm lakag incrasd th total building lakag by ovr 5%. Ths thr buildings wr constructd in 1967 or arlir, whil two buildings built mor rcntly (1998 and 27) had rlativly low mchanical systm lakag. This suggsts that improving dampr tightnss offrs a significant nrgy fficincy opportunity to xisting buildings and should b a considration for nw construction. Furthr work is rquird to assss th mthods, cost, and tightnss improvmnts of dampr rtrofits..3 Mchanical.25 Envlop, Dprss. Aftr Saling 119% /sf) M F (C g a k a.15 L ir A d liz a.1 r m o N 15% %.1 2% %.7 21% Elm School TF 1951 Middl School 1936 Small Offic 1998 Univ Library 1967 Elm School PS 1965 Library/Offic 27 Figur 4: Building normalizd nvlop and mchanical systm lakag 3.5. Mchanical Systm Building Prssur Effct This projct sortd th 15 minut building prssur and wathr data into /un or day/night s of opration. Figur 5 scattr and box & whiskr plots display th rlationship of building prssur with outsid tmpratur for thr of th buildings. Th Elm School TF building has thr air handling units, six rooftop units, and six fan coil units for th original portion of th building and th four additions. Som units hav outsid air and som us an conomizr opration. Non of th units or xhaust fans oprats at night and thr is no activ building prssur control. Th systm rlis on a prdtrmind balanc of outsid and xhaust air to maintain th building dsign prssur. Excpt for on hour morning and vning transition priods, th HVAC opration producd a positiv building prssur at th roof monitoring position and th majority of th building xtrior was undr positiv prssur during th. Th scond row of plots for th Univ. Library shows a mor xtrm xampl of building prssurization. For mildr wathr th prssur at th roof typically varis from +1 to +3Pa during daytim opration, but whn th outsid tmpratur is lowr than 4F th building prssur is consistntly abov 4Pa. Non of th four air handlrs has activ building prssur control. I insufficint or malfunctioning xhaust capacity that producs high positiv building prssurs and oftn causs ntry doors to blow opn. For both buildings, ignoring th ffct of HVAC opration

9 on building prssur would produc ovrstimats of air infiltration loads and of nrgy savings du to nvlop air saling. Building wrt Outsid Prssur (Pa) Elm School TF 15 For priods with wind spd < 5mph Building In w rt Outsid Prssur (Pa) un 5 Building In wrt Outsid Prssur (Pa) Outsid Air Tmpratur (F) Outsid Air Tmpratur (F) un un un 1 9 Outsid Air Tmpratur (F) Building Prssur wrt Outsid Prssur (Pa) Univ. Library Day Building In wrt Outsid Prssur (Pa) Outsid Air Tmpratur (F) Building In wrt Outsid Prssur (Pa) Library/Offic un Building In wrt Outsid Prssur (Pa) Building In w rt Outsid Prssur (Pa) Outsid Air Tmpratur (F) Outsid Air Tmp ratur (F) un un un Figur 5: Occupid and un building prssur with outsid tmpratur Th third building (Library/Offic) has activ building prssur control, but th prssur snsor for on of th air handlrs was malfunctioning. Th building did not oftn achiv its prssur st point of +1Pa and typically only maintaind a positiv building prssur at outsid tmpraturs of 4F to 7F. Th rmaindr of th tim th building was dprssurizd, with significant dprssurization in warmr wathr. For this situation ignoring th HVAC prssur ffct would rsult in undrstimats of air infiltration and air saling savings. 4. CONCLUSIONS Th buildings wr much tightr than th U.S. avrag rportd by prvious studis, vn though many of th buildings wr built bfor 197 and non was rquird to mt a tightnss standard at its tim of construction. Prvious studis hav suggstd that buildings in coldr climats ar tightr, so ths buildings follow that trnd. Our air saling rsults indicat that it is possibl to rduc th lakag of alrady tight buildings. Howvr, th saling potntial is bttr for lakir buildings, unlss invstigators can idntify concntratd laks

10 that ar inxpnsiv to sal. Th contractor stimats of physical lakag ara that would b sald wr lss than a third of th masurd rduction in lakag ara. IR scans and smok puffr invstigations confirmd that th spcifid laks wr succssfully sald, which suggsts that it is ncssary to improv mthods for stimating lakag ara. Th typ of tst and mchanical systm lakag has a significant ffct on building tightnss rsults that must b considrd for tightnss prformanc standards. Th lakag for prssurization tsts was an avrag of 22% gratr than that for dprssurization. It is unclar which tst is a mor valid indicator of lakag undr typical conditions. HVAC systms ar oftn dsignd to positivly prssuriz buildings, but on of th lakag paths (i.. loos door latchs) only occurrd at prssurs abov 25 to 35Pa. For half of th buildings, including th mchanical systm lakag incrasd th total building lakag by ovr 5%. Sinc th mchanical systm is part of th nvlop whn it is not oprating, that lakag can significantly impact air infiltration, and lakag rduction prsnts an opportunity for nrgy savings. For many of th buildings, ignoring th ffct of HVAC opration on building prssur would produc ovrstimats of air infiltration loads and high prdictions of nrgy savings du to nvlop air saling. Howvr, in som instancs HVAC dprssurization causd incrasd infiltration that would rsult in undrstimats of infiltration and air saling savings. 5. ACKNOWLEDGEMENTS Th authors wish to thank th Enrgy Consrvatory for th loan of quipmnt and staff assistanc that thy providd for th air lakag tsts. Many popl workd long hours undr advrs conditions to conduct th tsts including Enrgy Consrvatory staff: Ptr Burns, Paul Morin, Rob Nvitt, Gary Nlson; Cntr for Enrgy and Environmnt staff: Alx Haynor, Jrry Kimmn, Kirk Kolhma, Jol Lafontain, Dan May, Erik Mo, Tom Prbich, and Isaac Smith; and Bruc Stahlbrg of Affordabl Enrgy Solutions. This projct was supportd in part by a grant from th Minnsota Dpartmnt of Commrc, Division of Enrgy Rsourcs through a Consrvation Applid Rsarch and Dvlopmnt (CARD) program. 6. REFERENCES ASTM E779-1, (21). Standard Tst Mthod for Dtrmining Air Lakag Rat by Fan Prssurization, ASTM Intrnational, Wst Conshohockn, PA, 21. DOI: 1.152/E779-1, ASTM E1186-3, (29). Standard Practics for Air Lakag Sit Dtction in Building Envlops and Air Barrir Systms, ASTM Intrnational, Wst Conshohockn, PA, 21. DOI: 1.152/E1186-3R9, Emmrich, SJ, and AK Prsily, (211). U.S. commrcial building airtightnss rquirmnts and masurmnts. AIVC Workshop, Brussls, Blgium, 211. Emmrich, SJ, and AK Prsily, (25). Airtightnss of commrcial buildings in th U.S. AIVC Confrnc, Brussls, Blgium, 25. Emmrich, SJ, AK Prsily, and TP McDowll, (25). Impact of infiltration on hating and cooling loads in U.S. offic buildings. AIVC Confrnc, Brussls, Blgium, 25. Prsily, AK. (1998). Airtightnss of commrcial and institutional buildings blowing hols in th myth of tight buildings. Thrmal Envlops VII Confrnc. Dc. 6-1, 1998, Clarwatr, FL. US Army Corps of Enginrs ERDC, (21). Air Lakag Tst Protocol for Building Envlops, Air Barrir Association of Amrica.

11 Walton, GN and WS Dols, (213). CONTAM Usr Guid and Program Documntation, NISTIR National Institut of Standards and Tchnology. Downloadd from on Fbruary 28, 213.