Houses Need to Breathe... Right?

Transcription

1 Tight hou ar nrgy fficint, but good vntilation i ntial to mak thm halthful and comfortabl Hou Nd to Brath... Right? BY MaX H. HrMan I har it all th tim: Hou ar too tight. Hou didn t ud to mak popl ick. Th artion m wll foundd: Th mot riou chronic illn of Amrican childrn i athma, and th Environmntal Protction Agncy lit poor indoorair quality among it top fiv nvironmntal thrat. Ar tight hou poioning u? Thr no diputing th cau-and-ffct rlationhip btwn tight hou and indoor-air pollution. In thory, th olution i impl: If you build tight, you mut vntilat right. In practic, though, vntilating right i complicatd and controvrial. In 2003, I chaird an Amrican Socity of Hating, Rfrigration and Air Conditioning Enginr Indoor air pollutant air pollution uually mak u think moktack and xhaut pip, but indoor air i uually dirtir than outdoor air. litd at right ar om of th common pollution ourc arguing for good wholhou vntilation. 64 FINE HOMEBUILDING (ASHRAE) committ that pad th country firt ridntial vntilation tandard, which giv buildr and dignr guidlin for providing good indoor air whil kping utility cot low ( p. 69). Vntilation i manifold in hou ytm Bfor I go farthr, lt m dfin vntilation. Th word vntilat com from th Latin vntuilar, and it man to xpo to th wind. Although thi may ound lik om crp in a raincoat, th ral tory i mor complx. Vntilation i ud many way whn dcribing how a hou work: Thr crawlpac vntilation (oftn bad), vntilatd iding ambli (good), and roof vntilation (omtim bad, om- Moitur Moitur i not a contaminant in th uual n bcau watr vapor itlf i not an air-quality iu. But if th humidity i too high (a can happn aily in a tight hou locatd in a cold climat), it can lad to condnation, which can cau problmatic mold and fungi to grow. Can and bottl Toxic chmical (uch a pticid, paint uppli, and claning uppli ) that ar tor d around th hou can cau halth problm dirctly. Th itm arn t lim itd to th gara g and th claning -upply cabint ; many conumr product uch a comtic and a ir frhnr al o can cau indoo r-air pollution.

2 AN EXHAUST-ONLY SYSTEM REMOVES THE BAD AIR Exhaut fan Paivintak vnt provid rplacmnt air. Laundry room Th implt way to mak ur contaminant don t build up in a hou i to uck thm out with on or mor continuouly running xhaut fan. Thi approach i th lat xpniv, i th lat invaiv, and ha th advantag of working in hou without xiting ductwork. For wholhou vntilation, xiting kitchn and bath fan mut b lft running, a noiy propct unl you v got upr-quit modl. A bttr olution i to u a multiport fan (drawing p. 68) in th attic that xhaut many room imultanouly. Air lak provid unrliabl rplacmnt air. PASSIVE INTAKE Air pollutr In thi xhaut-only ytm, makup air com in through opn door and window, or through lak if you v got a laky hou. If you v got a tight hou, paiv vnt rv th am purpo. Th Thrmator vnt picturd hr com from and cot about $35. Similar vnt ar availabl from www. aldamrican.com and tim good). W r not talking about that tuff. Hr, w r talking about mchanical vntilation, uing fan to blow out old air (xhaut), uck in nw air (upply), or both (balancd vntilation). Laky hou ar not th anwr On avrag, th air in oldr hom i rplacd onc vry hour (1 ACH, or air chang pr hour) bcau oldr hom hav a built-in vntilating mthod that impl and rliabl: lak (or infiltration). Th avrag hou in th Unitd Stat ha about 3 q. ft. of hol in it, but infiltration i a prtty bad way to vntilat bcau it wat a trmndou amount of nrgy. you could platr that 3 ft. of hol rial Building mat d (VOC) nic compoun d toxic, Volatil orga r id n not b co may or may t cla of rg la th but thy ar air. Th und in indoor chmical fo aldhyd rm fo i C VO mot common in nginrd-wood d from glu u a particlboard. ch d paint product, u t and oil-ba Synthtic carp of indoor VOC. urc ar othr o Drawing: Don Mann. Photo: Danil S. Morrion. Pull cord opn and clo vnt. with $20 bill, and th work would pay for itlf in l than a aon. Sinc th oil hock of th 1970, hou ar tightr and bttr inulatd. Evn convntionally framd nw hou can b 5 tim tightr than th gnral tock. Many buildr and dignr ar tmptd to tak th Goldilock approach and to look for that lvl of lakag that i jut right, nithr too littl nor too much. Unfortunatly, thr i no hol for all aon. Th bt a laky hou can do i wat nrgy much of th yar and b undrvntilatd th rt of th yar. Won t opn window provid th vntilation w nd? In principl, y, but in practic, no. Popl ar prtty bad at ning xactly how much, how oftn, and for how long to opn th window to provid Biological Pt, dut mit, mold, and othr nano-crittr ar not contaminant by thmlv, but th particl thy hd can cau variou kind of allrgic raction and/or athma. Mit and mold rquir pcific moitur and tmpratur condition to grow and uually can b controlld by controlling th humidity. Biofflunt from pt can b difficult to control. Smok Smok fryin from ca g and a fih con ndl, to b t cont h), VOC ain part acco, an a d ic VOC minant, and oth l (oot in halt, many o addition r gaou f h p ro blm which ca to min cau.

3 optimal vntilation. Furthrmor, noi, dirt, draft, and crp in raincoat diuad popl from opning thir window. Indoor air uually i dirtir than outdoor air Bcau indoor air tart a outdoor air, thn grow mor pollutd from contaminant in a hou ( Indoor air pollutant, pp ), indoor air nd to b cland. Fluhing a hou with frh air rmov much of th indoor pollution. Th mot obviou way to control om contaminant i to iolat thm. Paint thinnr and othr poion can b tord in a gardn hd. Anothr way to control contaminant i to liminat thm from th contruction proc: U low-voc paint, low-mitting carpt, and olid wood, rathr than particlboard, in furnitur and cabintry. A third way to control th pollution lvl in a hou i to xhaut pac whr contaminant ar producd, uch a kitchn, laundri, utility/ torag room, and bathroom. But vn aftr you v iolatd, liminatd, and xhautd, thr ar till pollutant ourc that ar mot practically dilutd with controlld whol-hou vntilation. Good vntilation: Diffrnt path to th am plac Whn vntilation rmov contaminant, it your frind, but in doing o, it uually bringing in outdoor air that mut b hatd, coold, or dhumidifid, which cot mony. Jut bcau it cot you mony, though, don t man vntilation i your fo. Th nrgy aving of a tight hou mor than offt th oprating cot of a mall fan, not to mntion th cot of athma and allrgy mdication. Th trick i to dign a vntilation ytm that provid accptabl indoor air a fficintly a poibl. Th ytm dign will dpnd on whr you liv, but th ASHRAE vntilation tandard can guid you Prurizd/dprurizd Whn th inid of a hou ha a highr prur than th outid, th hou i prurizd (think of a balloon). Thi happn whn air i blown into a tight hou. Th ffct i to puh intrior air into opning in th wall and ciling. Whn th inid of a hou ha a lowr prur than th outid, it i dprurizd. Thi happn whn a lot of air i xhautd from a tight hou (uch a with a larg rang hood) without any makup air. Th ffct i to uck air through opning in th wall or ciling, chimny bing th biggt and mot obviou, potntially cauing backdrafting. Backdrafting Whn air flow oppoit th dirction of it intndd path, oftn through a flu or chimny. Thi can happn if th hou i dprurizd. In backdrafting, contaminant ar pulld into th hou intad of bing xplld, which can cau ickn or dath. through altrnativ. Evry vntilation ytm likly will b a littl diffrnt. In gnral, though, thr ar thr approach to whol-hou vntilation xhaut, upply, and balancd ytm ach a littl mor involvd and mor xpniv than th lat. Exhaut vntilation clar pollutant at thir ourc Th implt ytm, xhaut only, provid mchanical vntilation with a continuouly oprating xhaut fan (drawing p. 65). Thi fan can b a impl a upgrading your bath fan or a complx a intalling a multiroom xhaut fan. Th xhautd air i rplacd by air infiltrating through lak (in humid climat, thi can cau moitur problm). But rathr than doing o at th whim of th wathr, it i bing don at a tady lvl with th fan. With th quit, nrgy-fficint fan availabl today, thi option i chap and ay. Bcau it makup-air rquirmnt ar mall, a low-volum xhaut fan won t dpruriz your hou nough to cau backdrafting. Thi ytm alo ha th advantag that it can b ud in hom without ductwork. A downid i that thi ytm blow out hatd (or coold) air and, thrfor, wat nrgy. Anothr downid i that you don t know whr th vntilation air you r ucking in i coming from (or whr it ha bn). W d rathr not hav air from a garag or othr pollutd pac inadvrtntly bing brought into th hou. Paiv-intak vnt ar a impl way to offt thi problm (photo p. 65). Supply vntilation dilut pollutant throughout th hou A upply ytm ha th advantag of allowing you to lct whr th air com from and how it i ditributd throughout your hom. For xampl, frh air can com from a duct run connctd to th rturn plnum of an HVAC Thr dign choic for hot, humid climat In a hot, humid climat, ucking frh air into your hou can b a problm. You inadvrtntly can introduc 8 gallon of watr a day from th vntilation air. Whn combind with intrnally gnratd moitur ourc, thi i way too much. Thr ar thr dign option to conidr or combin. 1. Tolrat You can accpt priod of high-moitur lvl if you u moitur-tolrant matrial. Hard, clanabl urfac ar bttr choic than fuzzy on. U hardwood floor intad of carpt, or til, platr, or brick rathr than papr-facd drywall. 2. Diccat Gt th xtra moitur out of th air by condning it and draining it. Air conditionr can rmov moitur, but thy uually ar izd and dignd for controlling tmpratur. In om climat, thy won t dhumidify nough undr normal u. A bttr option i a tandalon dhumidifir or nhancd dhumidification gar. 3. Procratinat Som humid climat hav dry aon. It may b poibl to u rrvoir-typ buffr matrial that tor moitur during hot, humid priod, thn rla it during dry on. Exampl of uch matrial ar brick intrior wall, cllulo inulation, and olid-wood xpod bam. 66 FINE HOMEBUILDING

4 A SUPPLY SYSTEM REMOVES BAD AIR AND BRINGS IN FRESH Hou with a forcd-air hating ytm or with cntral air conditioning hav a built-in air-ditribution ntwork. A upply ytm u it to ditribut frh outid air through th xiting ductwork. But you till nd xhaut fan in th wt room. Th bt approach i a quit, continuouly running multiport vnt fan in th attic that draw from vral room ( p. 68). Exhaut fan ACTIVE INTAKE With a duct from outid th hou to th furnac rturn-air plnum, frh makup air i drawn into th hou by th furnac fan. A tmpraturand humidity-ning dampr ytm (picturd blow) intalld in th duct curtail airflow during vry hot and humid or vry cold wathr. Laundry room A parat rang-hood vnt fan i th implt, bt way to dal with contaminant from cooking. Air pollutr Frh air i brought in through a parat duct running from th outid to th rturn-air plnum of th HVAC unit. A dampr hut down air intak during tmpratur and humidity xtrm. ytm (drawing abov). Thi way, outdoor air i pulld in to th hou through th air handlr whnvr it oprat. Such an air intak mut hav control (uch a a timr or cyclr) to turn on th air handlr to mak ur thr i nough vntilation air. Thi ytm alo hould hav a dampr to prvnt ovrvntilating whn th hating or cooling ytm i oprating mot of th tim (vry hot or vry cold wathr). Without th control, thi upply ytm i jut a hol in th rturn duct, which i wor than a laky hou. Supply ytm mut tmpr vntilatd air to modrat tmpratur in all but th mildt climat. Th ytm abov do thi, whn thr i no hating or cooling call, by running th air handlr and mixing unconditiond outid air with larg volum of conditiond indoor air. Whil thi proc tmpr th outid air, it u a lot of Photo: Courty of Aprilair ( lctricity bcau th air-handlr fan i ovrkill for th amount of vntilation air bing uckd in. Balancd vntilation bring in th good air, banih th bad, and conrv nrgy Th bt way to tmpr incoming air whil rducing HVAC nrgy conumption i to u a hat-rcovry vntilator (HRV) or an nrgyrcovry vntilator (ERV) (drawing p. 68). Th ytm ar balancd approach that u th tmpratur and humidity of an xhaut-air tram (which othrwi would hav bn watd) to tmpr th air of a upply tram, thrby rducing th HVAC nrgy cot. HRV hat or cool incoming frh air and can rcaptur up to 80% of th nrgy that would b lot without thm. ERV ar bttr uitd for APRIL/MAy

5 A BALANCED SYSTEM REMOVES BAD AIR, BRINGS IN FRESH, AND CAN SAVE HEAT (OR COLD) Th problm with xhauting tal air from your hou i that you v likly paid good mony to hat or cool that air, and vnting it dirctly outid i lik throwing away mony. A balancd ytm with a multiport vnt fan (from $185 at or channling all xhaut through om typ of hat xchangr can mitigat th nrgy lo. Multiport fan vnt problm ara. Exhaut duct lad to HRV. Outid-air intak uck frh air into th hou and introduc it to th rturn-air plnum. Bathroom and kitchn xhaut ar uckd into th HRV/ERV and xhautd outid. HRV/ERV u hat from xhautd air to warm incoming air. Rturn air for furnac ACTIVE EXHAUST AND INTAKE WITH ENERGY RECOVERY Th bt approach to whol-hou vntilation mploy ithr a hat-rcovry vntilator (HRV, from $700; picturd blow) in cold climat or an nrgy-rcovry vntilator (ERV, from $800) in hot climat. Th unit, which can b incorporatd into a hou with or without xiting ductwork, bring in frh air and xhaut tal air. But in addition, an HRV tmpr incoming air with outgoing air, thu lowring th amount of nrgy ncary to condition th frh air. An ERV look and function imilarly, but it dhumidifi and cool hot, humid air, which rduc th load on th air conditionr. 68 FINE HOMEBUILDING A parat rang-hood vnt fan i th implt, bt way to dal with contaminant from cooking. Air pollutr Aftr giving up it hat inid th HRV, tal air i xhautd outid. Rturn-air plnum HRV u hat from xhautd air to warm incoming air. Outid-air intak uck frh air into th HRV, whr it i tmprd bfor it ntr th rturn-air plnum. Photo: Courty of Fantch (

6 Amrica firt ridntial vntilation tandard Until rcntly, not much had changd inc 1631 whn King Charl pad th firt vntilation cod (you had to hav oprabl window that wr tallr than thy wr wid). Bcau today hou arn t laky nough to provid frh air, th Amrican Socity of Hating, Rfrigration and Air Conditioning Enginr wrot a vntilation tandard. ASHRAE 62.2 i a minimum tandard applicabl to both nw and xiting hom (including mall multifamily on). Kp in mind that 62.2 i a tandard, not a cod. Think of it a a rcommndation that may lad to a nw cod rquirmnt. Tmprd air hot, humid climat bcau thy dry incoming air, thu rducing th work that th air conditionr ha to do. You till nd to clan up Vntilation i good at diluting gaou compound and mall particl bcau mall particl act lik ga. Thy mix quickly in th air and follow air currnt whn air i xplld. But larg particl uch a polln, pt dandr, and dut mit mut b cland up or vacuumd rathr than xhautd or dilutd bcau thy r too havy to mix with air. Othr larg particl, mi-voc, ar olid or liquid at room tmpratur. Whil thy r not gaou, a Outdoor air that i mixd with indoor air o that it i at a tmpratur that i not objctionabl (but not ncarily comfortabl). For xampl, a ddicatd outdoor-air ytm may tmpr 1 part of th incoming outdoor air with 3 part intrior air in th upply plnum bfor upplying it to occupid zon. with VOC, thy ar volatil nough to mit lot of gaou vapor. Thi i important bcau if you filtr out SVOC particulat, you havn t rally don anything until you clan th filtr; th SVOC kp mitting gaou vapor from th filtr. If you don t rplac filtr on your HVAC ytm rgularly, th ytm itlf bcom a contamination ourc. Th thr vntilation ytm dicud hr ar by no man comprhniv; thy can b combind in variou rcip to mt particular condition. In addition to climat and hou tightn, cot can b a big conidration, but it houldn t b th major on. B ur to conidr long-trm durability and maintnanc rquirmnt. Sytm with hat rcovry (HRV/ERV) rquir a lot mor maintnanc than tho without. Sytm with multipl filtr or rquiring aonal adjutmnt can b confuing. Tight hou ar good, and thy hould brath Excivly laky hou ar on way for a hou to brath, but not th bt. Whil thr a lot of ongoing rarch and a robut cholarly dbat on th bt way to achiv accptabl indoor-air quality, building cintit all agr that hou nd to brath. A hou bcom highr and highr prformanc, thy nd to brath in a tady, raonably controllabl way. W cannot afford to lt thm brath at th whim of th wathr or with window only. W alo omtim nd to b abl to hav thm hold thir brath whn condition outid ar xcptionally bad. Only with dignd vntilation ytm can w mak ur that indoor-air quality and nrgy fficincy advanc hand in hand. M Dr. Max H. Shrman i a conulting building cintit and phyicit at Lawrnc Brkly National Laboratory in Brkly, Calif. Th major rquirmnt of 62.2 ar: Whol-hou mchanical vntilation Exhaut, upply, or balancd vntilation. For a typical hou, 50 cubic ft pr minut (cfm) will do. Mchanical xhaut in kitchn and bathroom In addition to th whol-hou vntilation rquirmnt abov: Kitchn: a ur-oprabl vntd rang hood of at lat 100 cfm; or a fan giving 5 kitchn air chang pr hour of continuou or intrmittnt xhaut. Bathroom: a ur-oprabl fan of at lat 50 cfm; or a continuouly oprating 20-cfm xhaut fan. Fan mut mt prformanc lvl A third-party rating i rquird for airflow undr raonabl oprating condition. Th ound rating i 1 on for continuouly oprabl fan and 3 on for intrmittntly ud kitchn and bath fan in itm 2. Combution applianc mut follow building cod For om circumtanc, vntd combution applianc ar prohibitd from bing indoor. Bcau 62.2 i not about combution afty, it addr th fw ca whr combution and vntilation quipmnt can intract. Garag duct ytm mut b airtight Air handlr or rturn duct in an attachd garag mut b ttd for tightn. Whil tight duct av nrgy, 62.2 t only minimum rquirmnt to protct indoor-air quality. Particl filtration uptram of air handlr Dirty duct and coil can bcom a pollution ourc, o 62.2 rquir platd furnac filtr (MERV 6 or bttr). To clan th air inid th hou, mor aggriv filtration would b ndd. april/may