AIVC 11891 4229 (RP-806) Placement of Ventilation Air Intakes for Improved IAQ
Brian A. Rock, Ph.D., P.E. Kelly A. Moylan Member ASHRAE Student Member ASHRAE
ABSTRACT to produce a design guide, and to recommend any needed research. The ultimate goal of this and related projects is to ASHRAE Research Project 806, Design Criteria fo r improve indoor air quality (IAQ) in commercial and institu Building Ve ntilation Inlets, reviews existingknowledge of the tional buildings. placement of ventilationair louvers, produces a design guide, and suggests additional research, all with the intention of This paper discusses previous research effortson building improving indoor air quality in commercial and institutional ventilation inlets and outlines the material in the project's buildings. Decisions about intake and exhaust placements ''Designer's Guide to Placement of Ventilation Air Intake made early in the architectural and HVAC system design Louvers" (ASHRAE 1998a). This ''Designer's Guide" is a less processes will impact occupants over the life of a building. technical description of the problems associated with intake Such placement decisions, therefo re, require proper consider placement and presents some example calculations. The ation. Thereis little guidance currently available to designers, project's "Literature Report" (AS:H:EAE 1998b) covers the but research efforts in this area are expanding. previous research effortsin somewhat more detail than can be Previous research efforts andstandards relating to venti presented in thispaper. A lengthy bibliographyis provided too. lation air intakeplacement are described in this paper. However, more extensive coverage and a lengthy bibliography are AIRFLOWS IN HVAC SYSTEMS providedin the project's "LiteratureReport. " In "A Designer's Figure 1 shows anidealized air-handling unit (AHU) and Guideto PlaceTTrent of Ve ntilation Air IntakeLouvers" fo r the airflows typical of single-zone packaged or built-up HVAC project, the phenomena, standards,and design experiencesthat systems in many commercial, institutional, and industrial affect the placementof intakeair louvers arereviewed using less buildings. Of the packaged HVAC systems, rooftop units technical text, many graphics, andexample calculations. (RTUs) arevery popular.Some of the returnair being retrieved More research is needed on ventilation intake placement from a thermal zone is typically recirculated and some is fo r common commercialHV AC systems with rooftop,through exhausted through a grille that penetrates the envelope of a the-wall, and at-grade louvers. Most existing knowledge is packaged HVAC unit or a building. Outside air is brought in derived fromthe many studies on industrialstack exhaust-gas through an air intake louver. If not part of a packaged unit, reentrainment and not common HVAC geometries. Thefind these louvers and grilles may be on or in the roofs, in stacks, ings of such future research and a summary of this project's inthe buildings' exteriorwalls, or through grates in sidewalks, "Designer's Guide" need to be included infuture revisions of forexample. The outdoor airbrought in throughthe louvers by ASHRAEHandbook chapters. theAHU is combined with the recirculated airto form mixed air. This mixed air is then conditioned and delivered to the INTRODUCTION zone as supply air (ASHRAE 1997a, Chapter 25). The purpose of ASHRAE Research Project 806 was to Most residential buildings in theU.S. rely on infiltration review existingknowledge of ventilationair inlet placement, for maintaining acceptable indoor air quality and, thus, have
Brian A. Rock is an associate professor and graduate adviser and Kelly A. Moylan is a Master's student in the ArchitecturalEngineering Departmentat the University of Kansas,Lawrence.
THIS PREPRINT IS FOR DISCUSSION PURPOSES ONLY, FOR INCLUSION IN ASHRAE TRANSACTIONS 1999, V. 105, Pt.1. Not lobe reprinted in whole or in part without written permission of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 1791 Tullis Circle, NE, Atlanta, GA 30329. Opinions, finding&, conclusions, or recommendations expressed in this paper are those of the author(s) and do not necessarily reflect the views of ASHRAE. Written questions andcomments regarding this paper should be received at ASHRAE no later than F*uary 13, 1999. ..
Figure 1 shows thatoutside air is usuallydelivered to ther OutsldB Air MiXf1dAir Heating Coll Supply Air Fan mal zones as all or partof the supply air.To ensure proper IAQ, (OA) {MA) (HC) {SAF). i.1 the designer needs to consider whether the outside airwill be ·;:. ' z introduced consistently and, within reason, wllat conditidns Louver % ..; .. % ' • �,;-' ; are likely to occur over the expected life of the HVAC system Filter Cooling Coll" . Supply Air ;\ thatwill affect thequality of the outside air.For example, the (F) (CC) '! {SA) exhaust air �pown in Figure 1 is considered "used" and thus not suitable for ventilation air, so reentry needs to be reduced Outside Inside t Rei:lrr:u/atlidAir (CAJ,. to an acceptable level• Because louvers and grilles are typi Dampors Return Air ; , ; callyin fixedloca tions.1 their originalplacement will influence (D) (RA) the quality of outside air introduced to buildings over many z ' Grllle % +; + years. ' .. Exhaust Air Return Air Fan Louvers and Grilles 1 {EA) (RAF) From a simple fluid dynamics point of view, a louver or grille is unnecessary unless a particular downstreamdirection Figure I Airflows and equipment terminologyfo r a foran airflow is desired. Having no restriction in an outside or simple zane all-air air-handling system exhaust air duct as it passes through a building envelope or (ASHRAE J998a). packaged HV AC unit would result ina lower airpressure loss, no provisions for drawing in outside air through theirHVAC and, thus, reduced fanenergy use, rather thanhaving a louver units. A common exception are apartment and dormitory or grille in place. However, louvers and grillesare installed to buildings with centralized ventilation systems. Modem help keep moisture, insects, birds, leaves, and trespassers out commercial and institutional buildings in the U.S. primarily of buildings and equipment. They can also provide a more use the airflows, as depicted in Figure 1, to provide forced or aestheticallypleasing appearance than just darkholes in build mechanical ventilation. Industrial buildings may use infiltra ings and HVAC units. tion, forced ventilation, or both. This project, therefore, For a nonmanufacturer-specific introductionto the phys focused on the placement of forced -ventilation intakes in ical descriptionand specificationoflouvers andgrill es, see the commercial, institutional, and some industrial RV.AC Application :Manual for Air Louvers- (AMCA 1993). This systems. However, the principles discussed in this0paper, the booklet covers topics from louver design to construction "Literature Report," and the "Designer's Guide" ca.iialsQ p� details. AMCA'sbooklet and themanufacturers' catalogs that applied to residential buildings that utilizeforced ventilati.9n. were reviewed as part of this ASHRAE project did not give much guidance to designers concerningplacement of louvers . u and grilles and the placement's ..effect on a;d.90i:airquality . Ventilation .. - ) . • •' '' .,r r - Good indoor air quality is required in buildings to nralli� OUTSIDE AIR POLLUTANTS,_, ::· : . � -.r·. c� i'. -i ··· �c'c . tain healthy living and productive working environmlnts. Basic ventilation design assumes airborne pollutants Therefore, a goal in the design of the ventilation system is to generated V(ithina buildingcan be diluted b)'.the introduction ensure thatoutside air brought into the system is of high qual of outside air.This as��ption that outdoor air is cleaner than ity,if possible. The cleanerthe incanting air, the less treatment indoorair _dqes not neeessarily hold truewithin an urban area is required and, therefore, the less costly the system. where, forexample, 'Y.ehicle exhaust, gaseous industrialemis Ventilation air is definedin AN SUASHRAEStandard 62- sions, and/orair stagnation aff ect th.equalify of theoutQ.oor air. 1989, Ventilation fo r Acceptable Indoor Air Quality (ANSI/ Although the literature addresses all thesesources of pollut ASHRAE 1989) as outside air or suitably treatedrecirculated ants, by far the most prevalent topic is the reentry of exhaust air.Where theoutside airis knownto be of unacceptable qual fumesfrom a fixed,.lgi.own source.into a-nearby ventilation air ity, treatment of the outside airand/or recirculated airmay be intake. Other related'issnes addressedin the literature include ' ' I required.Designers often considerthe outside airto be accept wind effectsoi;i HVAC'system performanceand thermalstrat- able, so it is used directly to dilute airborne contaminants ificationof theatmosphere. , ;· ' ' · ' within buildings. Only some filtering of themixed airis typi Standard62'�}'Ventilation Rate Piocedme"requires that cally provided to remove larger particulates.However, after a certain amount of ventilation air be delivered to building reading this project's paper and the "Designer's Guide," occUpants (AN°Sl!ASHRAE 1989). If the building's HVAC designers should give further thought to the condition of! arr systen{exhailst aihvas'·so'mehow sii'bs&litially reentrained, ' passing through air intake louvers. This is especially impor the ventilation system�·woriid not fully-p �ffonil its intended tant in dense urban areasand other areas known to have ques functidn.I:fot the · natureof 'aiie:iliaust airplrline limits its effect tionable outdoor air quality during significant portionsof the on a nearby ventilatioii'air intake :Vaiyi.ngajrflow patterns and year. turbulence near buildings usually pfevent· - a well-defined
2 4229 (RP-BOS) e:xhaustplume andenhance dilution. Wind directionchanges To reduce this problem,_ likely outdoor smoking locations frequently,thus affectingdispersion andreentrainment.Much should be considered when positioninglouvers. For an exist of the li�erature reviewed for this project investigates this ing problei;nof this type, a solution couldbe to provide signage plume beb,a:v�or (i.e., ASHRAE 1997a; Halitsky 1963; and an 8lter;native indeor and/or outdoor smoking location. Meroney 1982; Wilson 1979). Having the�architect provide indoor smoking lounges, or at Theentrainment of exhausts can cause problems ranging least c�ve;Cd exteridr smoking areas away from air intakes fromthe introductionof nuisance odors to potentiallyharmful and entrances,should enhance smokers' as well as nonsmok ,contaminants. A proposed revision of Standard 62 classified ers' comfort and propuctiyity. exhaust airbased on the use of the space from which the air Of the people wliciperish in building fires,roughly three came. Separation dis�ces recommended by this now-with quarterdie due to smoke inhalation and not of direct exposure drawn draftstandard were based in parton tlle exhaust air clas to flames. Unfortunately, HVAC systems can contribute to sification and therequired dilution factor. smoke introduction to and distribution through buildings. Drift from cooling towers may pass through the louvers NFPA 92A-1996, Recommended Practice for Smoke-Control and potentially aid microbial growth within airdistribution Systems, in Section 2-3.3.1, gives only general observations systems. Water in the cooling towers themselves may provide on louver placement (NFPA 1996), but does contain other a breeding ground for microorganisms if not properly main useful information on smoke management,as does Design of tained (Kundsin 1988). But adequate separationbetween cool Smoke Management Systems (ASHRAE1992). i�g tower discharges and air intakes can reduce the time averaged admittance of drift. Vandalism and Terrorism Mechanical rooms with air handlers are frequently Of increasing concern in some buildings are acts of located nearloading docks to allow easier equipment replace vandalism and terrorism. The louvers and grilles arepotential ment andto consolidate potentialsources ofnoise. Outdoor air points of illegal access to buildings by people, so their place intake louvers are often placed too closely to these loading ment and construction are important.Also, intentionfilintro docks in attempts to keep duct runs as short as possible. Figure ductionof offensiveor potentiallyharmful gaseous substances 2 shows a loading dock withan intake louver placed directly is of concern. Research and design experience is needed on above. To make matters worse, the dumpsters arenearby, as is these issues. the building's exhaust grille: The propped-open door itself allows some indoor air to be recirculated as well.\'' Dlt.UTION
•:..
, ·' F�e 3 shows that given the less-than-ideal conditions Smoke that exist around real buildings, there will be some degree of A problem enhanced by indoor tobacco-sm�kingrestric reentrainment at times ofexhaust air,sewer fumes, and even tions is that E_eople will instead smolj:e outdoors and poten industrialstack gases.This reentrainmentwill be highly tran tially near air:"'inllies . When such outdoor environmental sient depending on the conditions of the exhaust and the tobacco smoke (ETS) is dra� into a bp.ild.ing, on�,intended sµrrounding environment. Thebehavior ofjets is discussed in effectof the indoorsmoking restrictions has been diminished. som� detail in the "Space Air Diffusion" chapter in 1997 ,• ·� 1: �:-. ·�;;. -;� • : ' .;. J •,. , - -:...
c.... C_ outlet f5 .... -+ Jet
Cc'c Re entrained .l Fluid or "Reentry• Inlet ) / c .... � I)� �� · '. �� -· � '·· J �· .? !H"': .�. �· t: �... ! .;._:.\� .... 2 l!xample of"cip .oor; o.u!st'!.e air. inlet /J!UY�r "Still" air in the su"ounding environmentwill Figu�� , . • . ., eJqc;.� nt near a l?
••' •. . t"'';is over a doorway and closet.. to.an. �haust• • the concentration of some airborne substance • I ta , ...... , 'grple, vehic1.4lar exhausts., f!nd.dumpsters . , of interest(ASHRAE 1998a). (ASR.JW:. 1998a). n.
4�29 (RP-806) 3 ASHRAE Handbook-Fundamentals (ASHRAE 1997a) and Free flowing wind is usually highly turbulent, and the instan in many older fluidmechanics textbooks. A goal in the place taneous wind velocity can double or even reverse veryquickly. ment of intakes andexhausts is to minimize this reentrainment Thus, the air pressure at the intake louvers varies and affects to an acceptable time-averaged value. Factors that influence supply air fanperformance . Static pressure within a building the degree of reentrainment are the velocity, flow rate, and can vary significantly if the inlet pressure is not adequately direction of the exhaust; the flow rate and velocity of the controlled. To maintain a desired static pressure within a intake; the height of the exhaust stack; the distance between building, Houlihan recommends placing the outside air intake the exhaust and the intake; thebuoyancy of theexhaust plume; in anarea where there is usually no wind. However, a no-wind local wind and pressure differences created by airflow over condition may only exist in a semi-enclosed areathat is likely buildings; and interacting surfaces su c.frras roofs, walls, and to be a recirculation zone (ASHRAE 1997a). Placing the screens (ASHRAE 1997b). intake in such a location may reduce the problem of varying The dilution factor (D) is frequently used to express the system pressurization but may increase reentrainment of maximum desired time-averaged reentrainment of some contaminants. exhaust components. The dilution factor on a mass basis is (ASHRAE1997a, Chapter 15) Wind Two importantfeatures of airflow near buildings are air (1) recirculationzones and turbulence.In a recirculationzone, the concentration of a contaminant is increased because reduced where Ce is the concentration in lbm/ft3 (kg/m3) of the airflow passes through the zone's boundaries as compared to substancein the exhaust air duct or stack, and C is thedesired freestream flow. But turbulence increases the rate of mixing maximumconcentration in theintake duct in lbm/ft3(kg/m3). and, thus,dispersion of a contaminant into thesurrounding air. The dilution factor may also be evaluated on a volume basis Wind tunnel studies have been popular for studying with common units used of parts-per-million parts (ppm). If airflow near buildings as well as for observing the effects of the molecularweight of the pollutant is similar to airand the surroundings. For example, Barrett et al. (1979) examined dischargeand intaketemperatures are close, thenthe massand chimney height in a hilly terrain to examine dispersion of volume dilutionfactors are assumed equal (ASHRAE 1997a, industrial contaminants. Chapter 15). The desired values of D for common HVAC Schuyler and Turner (1989) used wind tunnel experi applications are typically five for exhaust air froma general ments: to deterpline ifthe dilution equations in Chapter 15 of office space but can be 50 or much higher for potentially the AS!fRAE Handbook (ASHRAE 1997a), could be used to hazardousairborne effluents fromindustrial stacks and fiiine ft_nd, potential cpntamination problems. The Schuyler and hoods. Turne!'.study us� one isolated building of a simplegeometry. Safety and odor, threshold levels and freqµency ofreentrain FACTORS AFFECTING REENTRY AND DILUTION· ment ·based on wind speed data werei§tudied.. The authors :c-o,nc�uqed that varyi}ig wind �ections greatly affected the Location of Pollutant Sources amoll.nt.. of reentrainment. Buildip.g geometry,::especially In most of the literature and, thus, in this study, it-\Vas up�.in��obstrUpti()ns, w�r�othei: major factor. :The·.·authors assumed that the locations of building HVAC system exhaust recommended that the equations iDChapter 15 forseparation and otherpollutant sources were fixed. Then, thedecision to· be distancesbe used to identifya need forfurther study. They also made is the placement of the ventilation intakes in relation· to concluded thatthe chapter's equationsmay be used in design these fixed sources. Although exhaust stack design will not be but only with conservativestack heig}?� andrintak�loc.ations. discussed at length, it is necessary to understand the results of •·1• ·The prev�_n,g,wi�d �ection;�a"speed f,�i:�·lo��on_ such design decisions. Referto the"Airflow Around Buildings" -may 'be Used m HvAC design but·are no(t]�cessarily the 1).est :chapter in 1997 ASHR AE Handbook-Fundamentals for o i le '-desi�- ;n'\'.�ria. $e :R�e".�g��d �99. n,. . tl1e''.sJP.g furtherdiscussion on exhaust stack design (ASHRAE1997a). directioii· that' occurs most o�. n. dtID.qg_a, easo��of in�rest. t • •• ,.. .• ') ,. -\ l t. . ' : <. •• ' . .• • . ACGilI(1995) gives two optionsfor calculating,the posi Ho'Y�vet, wllids may�IAe frQm any , directiqn at .any timer. In tion of the airintakes in relationto exhaust stacks. The first is acfdltion,an area'sp h'b�boo prevci.ifuigwjnd may not be ac,cµ using thegeometry of a typical plume spread to find an ideal rate'for a p!tlticUiai btiilding thatbaS i�.o� .inicroelimate. ized intake location outside of the exhaust plume (Wils·lfo Airflow per-Penmcul�ly appr�aclrlng the upWind f�ce,qf 1976). The second method is using dilution calculations as a building stagnates (Chapter 15, ASHRAE 1997a), as shown A found in "Airflow Around Buildings" of the SHRA.E Hand in Figure 4. Partof the airflowthen proceeds up_ cµ;d_oy�i; the book-Fundamentals (ASHRAE 1997a, Chapter 15). building while the otherportion of the airflow enters a recir . ·,·) culationzone towardthe bottom of thebuilding's 'upWind face . Pressurization The reentrainment ·of the building· s 'exhaust an- ma"V'be Houlihan (1965) looked at the effect of wind pressure:on reduced or eliminatedby placing theexhaust grilleon theroof through-the-wall intakes and pressurization of a clean roam. or on.the upper-,pottiori'of the building's'faeeand' by ptabng
4 4� (RP-806) ,' ' Recirculation Cavity Bounda Upwind Velocity Profile rv, Uc U(i!!)
High Turbulence Zone Boundary
.,
Figure 4 Wind-driven airflow over buildings creates recirculation regions and deflects exhaust plumes (Wilson 1979).
the intake louvers on the lower portion ofthe building's face. so they do not affect placement of air intakes from a thermal Doing so, however, would allow street level contaminants to point of view, , ' , .. be taken into the system. This is a problem especially in congested urbanareas where vehicularexhaust fumesmay not MPDEL BUILDING CODES
be well dispersed at times. ,- � The dimensions of the upwind faceof a building'3.ffect the " �'' Building codes vary by location. Most local codes are ·resulting airflow recirculation regions. V(tlson's dilution :l;�ed �n national 011 international model codes and are formulas (1976) used a scalingfactor based.on the height and ad�pted inwhole, in part,or with amendments by local juris widthof the upwind face. Also, anyprotrusion above the inain dictions.The UniformMechanical Code (UMC), which is one roof level creates a recirchlation zone in its wake, and, for such model code, was prepared by the International Associa example, an L-shaped building would have a recirculation tioh.ofPlumbing and Mechanical Officials (IAPMO) collab zone in its interior comer (ASHRAE 1997a). Additionally, a orating with the National Association of Plumbing-Heating building 'may be located within the recirculation z'ohe of' a Cooling Contractors (NAPHCC) and the Mechanical neighboring building at tiines,"and, thus� reentrainment of its ,C,ontractors Association of America (MCAA) (IAPMO own and' the:·neighboring 'builoing's eXhaust'ris''�b:thethnes .19.97a).:TheUMC addresses theinstallation and maintenance increased. - - '· ·• � · � ': t ,.,. .,_of., J .I ' •� r heating, ventilating, air-conditioning, and refrigeration systems. The Uniform Plumbing Code (UPC), also prepared Diffusion of Contaminants : - :;,. : . · '. . i� · .. ':J . • I • . •r' ·• , by the IAPMO with NAPHCC and MCAA, addresses build Much of the literature addresses diffusion of r.building ing potable water and sanitary systems (IAPMO1997b). · ''exhaust �nies':'f.?r exim:ple HaJ.itsk);'(��63) · ���«��ed the . ' : Both the UMC and UPC are updated and published w : tli:eory of diffusion. It is 'asstimed in. most s,tucljf�· that t:p,e ''ibree-year cycles. Although local jurisdictions may want to greatestcont:rlbutor t6 the'contaminatioiofventilation int3.ke base their ordinances on the most recent versions of model air·is the e�aust frorfi� e.'s�� �uil��g. Al�ough ��tomo codes, thelocal review andapproval process may mean that bile exhaust fumesil.nd eXhaust air tt9m_neighboring buildings the current local codes referto model versions that are three, also affected the their reiative impact is .. ' ·� ' dverB.i.i• � �qualit}rl , ' . greatly reduced by'therr Clistaiice"fro,mbuilding a 's ventilation 1�Uc.,or many more years old. .. ���. ·' ·� ·1 w�C - • ' •. l -., .., • , . . t. Ifill' t. '·' intake. : · The multitude of local codes affecting the placement of .. - · .::•. :i ·-.: ' {;._;...... i1 ;: ��; n.:3.�;·�: � ! ;.,,
.. · ventilation air intakes cannot be addressed in this paper, but at <�:.'·''' '-' ::.. : .: · ·:;·.• - �-:· '�- · -·�- Temper ure some applicable portions of the model 1997 UMC and UPC . ,· ""II .:• ...._/ :- •. . .. ·."i.. ... ' ,Segal ::<1989)· de�cribed .¢e iteµip�Jature profiles in are presented in the project's "Literature Report" (ASHRAE out�oor airnear gra4e,�d how the profi,les_(!hangehourly and 1998b). In general, thesetwo model codes do not say specif through the seasons. Segal stated, howeJ er. fh,at the vertical ically where to place the ventilation air intakes but ratherhow temperatw;e , adlents1within 3.l} urb� c(!r:e,are·insignificant, fatJaway to place exhausts in relation to intakes.
4229 (RP-896) 5 DESIGN GUIDELINES _) ij approach that allows any design method to be used as long as acceptable indoor air quality is demonstrably achieved and "Airflow Around Buildings," ASHRAE Handbook maintained. The ventilation rate procedure is a prescriptive approach that requires fixed ventilation rates based on Due to wind, airflow over buildings is typically turbulent expected occupancies. and dominated by forcedconvection and not buoyancy-driven flow. As the title implies, the "Airflow Around Buildings" Most HVAC designers curr�ritly use the prescriptive chapter of the ASHRAE Handbook describes in depth the approach but performance-based ·-ventilation systems are airflow characteristics near buildings (ASHRAE 1997a, increasing in popularity. Because some airborne pollutants Chapter 15). Equations are given to calculate the expected come from sources other than people, the next revision of time-averaged dilution for a given exhaust stack-to-intake Standard 62 for new commercial and institi:itional buildings, configuration.The chapter goes into much detail on thedesign when adopted, will likely split the necessary'ventilationrates of exhaust stacks but just briefly mentions the concerns in into two parts based on zone floor area as well as occupancy. placement of ventilation air intakes. Cited concerns include Ifforced ventilation is used. tD pmvide ventilatio�rajr. the toxic building exhausts, automobile traffic,kitchen emissions, end result of applying ASHRAE Standard 62 is that design dust from streets and plants, evaporative cooling towers, rates of outside airmust be admitted to buildiiigs through air .,emergency generators, plumbing vents, loading docks, archi intake louvers. Some "used" air will be exhausted thro�gh . tectural screens, and heat exchangers. The chapter recom grilles at rates needed to maintain the desired zones' pressur mends placing intakes on the lower one-third.of the building izations. Separation distances must be set to reduce reentry of but high enough to reduce introduction of ground level this used air to an acceptable level. contaminants such as dust and vehicular exhaust. The center ! . of the roof is another preferred intake location. The chapter ASHRAE Standard 62R also recommends having exhausts exit via the roof but away from the intakes. Requiring specific, enforceable separation distances is being considered in the revision (R) of Standard62. Standard ANSVAS HRAE Standard 62-1989 62R has not been approved by ASHRAE or ANSI at the time of this writing. Its revision has been divided into 62. lR for The current version of ASHRAE Standard 62 was commercial, institutional, and bi.$h-rise residential buildings approved in 1989. Much knowledge and experienc�.9n ��pa arid 62.2R for low-r;ise residences. Standard 62 is now under ration distances and IAQ has'b een gained in the' Irv. C<&R ) � utii1 contin�ousreView, �o receipt of comments and revisions will research anddesign conununity since Standard 62's lastreyi- '·be ongoing. The August 1996 draft version, which has been sion. However, until a revised version of Standard 62 · is �ihdrawii...... • • gives-·insight intp �!the ...., direction- that codes, approved andadopted into local buildtng codes, the p visions ,, , • " • • '·· · concermilg separationdistances, areheaded. This draftof 62R of Standard 62-1989 are considered the "sta'ndards of prac · included Uie mininiuni separation distances or "setbacks,'' tice." Concerning airintake louver placement, Section 5.5. of given in Table 1, between air intake& and, pollutant sources ''' the standard states otherthan building ��austs. _ Ventilation systems shouldbe designed to prevent . �1?r: · · 'in� Wittldr'.ii�· ii..�i�w dr.ift . of 62R'.'.�a.s to require tp.e condensation_ fA t;I� '"11 r I' l• 11.1 • l· , _-ftl o.. •' • - trainment of exhaust contaminants, Qr.. 0 M!\.../\ limits water on I 'penetr�on. . through louvers .and freeze-ups (or both), and growth of micr'borgilnis:m�:-_ _ ' : es.•. bii:d. · sc��7�:��.?n 'lop.�e· �d '�· .p.oods on RTU Makeupair inletsand exhaust air outletsshan be located ,:'. �
to avoid contamination of themakeup air. Contaminants "·:u ·" " · , :,,-;.;.1 -":.·-'-TABLE 1' from sources such cooling towers, sanitary vents, a8 Air IntakeMini mum Separation Distances (Sm;,J vehicular exhaust fromparking garages, loading'docks, .. and streettr affic should be avoided. · , ,. Object -- ft m · Also, in Section 5.12: �� _, Property line f,. . . � ; � 3 ., ·l � Special care should be taken to avoid en,trninment of _ Gara� edlfy;loa�are"a, or drive in queue, . · - 25 7 moisture drift from cooling towers into the makeup air . :·.> and vents. (lane) ' . . -·'""· building '�"" . ·'"''·" v�"'q ..,,_ &ii•,_,�- ,. .. ., Dri�e�iv·ofstreef-· 10 3 Only this general guidance is given to designers mthe Limited access highway 1989 editionof Standard62. No specific requirements such as 25 7 •• - o']• '.l .. � defined minimum separationdista nces are given.1.oc'itl Mantles or ledges -..�<. ,. · � C.- hhll d · 3 1 ing c�des, however, may already have such requirements, or - !Landscaped grad�-(lapj:lscapipg) - .. :,·. . 1-. ... ;'"'\"'{.._. 6 l possibly, none at all. ":-,_, , ... �:.- ."- ··- Roof or (soil) grade ',...... Standard 62 describe& two approaches forthe selectionof 0.75 0.25 I'- ''o\ 'I , ·:J._ • .,l . • ventilation rates: 1) the IAQ procedure and 2) theventilation Cooling tow"ers (wetted surfaces, ,not their,air,� 15 5 ·- rate procedure. Tu.e IAQ,procedure is a performance-based discharges)
6 ";(�(RP-806) intakes. Also, various classes of exhaust air were defined and nest, the grade, landscaping,maximum snow depths, and cool limitati.9ns on recirculation of each type were specified. ing towers. The equation . - Thedraft of Standard62R was to require thatoutdoor air """ : { . ·� be assessed for contaminant levels based on national ambient s = 0.09. JQ;(JD��) (2) airquality standards (NAAQS) set by theUS. Environmental l' . ProtectionAgency (BP.A).Although thisassessment was to be in IP'units, or required, the draft did not require that the incoming air be treated even if the air quality was poor. . = 3) The location of v.entilation airintakes was to be based on s o.04. JQ .( JD-D ( the distance from any local contaminant soure mend using wind tunnel tests for design purpose.s.. .o '.' I ., ;, .. �ti,The .proceeding �d much more literature, various manu Model in Standard 62R facturers' catalogs, and trade publications were reviewed to '.' determine the most current guidance on intake placement Table 1, from the withdrawn draft �tandard 62R, lists availableto HVACdesigners .'- Thisproject's (RP-806)primary ·separation distances frorll' common . contaniliiant' ..sources. resUlt1is thefuSt edition of "A Designer's Guide to Placement ;_ Minimiim· separation Cli�tances �er� deffu.ecf the air 'ffom . of .V�ntilati�n Air Intake Lou�ers" (ASHRAE 1998a). The - intake to the pro'Pertiline, drivetvay, highways,'aridany " areas "D�signer's,Guide'' presents much of the material covered in where vehicles would be _igling; ledges where birds would this paper and the project's "Literature Report" (ASHRAE l 998b) b�t in a much less technicalmanner for the target audi 82 ence of architects and HVACdesigners early in theircareers. The ''Designer's Guide" includes many photographs, <::. diagrams, andsample calculations intended to give direct help in 'making louver placement decisions. The authors fully RTU expect that the "Designer's Guide" will require regular revi sions as knowledge expands on separation distances for ,epIDillon HVAC situations, for example. • :. 1 _,. � . CO.NCLUSIONS AND RECOMMENDATIONS , , · , ASHRAE Research Project 1 806 is a review of the Figure S The "s etched-stri11g''. distqtt e: ·s,''is the· n:. phenomena, standards, and design experiences that affect the separation distance betweel} exhaust or· � placement of intake air louvers with the intent of improving some other pollutantsour:ce and iinair intti/Ui . ., . ' ·. " .. indoor air quality. Decisions about intake and exhaust place (ASHRAE1998a). ments made early in the11itchitectu.ral and HVAC system 4229 (RP-aqs) 7 design p�ocesses will impact building users over thelife of the AMCA. 1993. Application manual fo r air louvers, AMCA building, so such placem1;mt decisions require proper consid Publication 501-93. Arlington Heights', Ill.: Air Move eration. However, there is little existing guidance for design ment and Control Association. ers, but researchon this topic is continuing. ANSI/ASHRAE. 1989. ANSIIA SHRAE Standard 62-1989, ., ; The majority of the previous research studies looked at Ve ntilation fo r acceptable indoor air quality. Atlanta : the reentraimnent of industrial process exhaust fumes from 1 American Sociefy of Hea ting, Refrige, rating and A.j.r- stacks into the ventilation systems of buildings. More research ConditioningEng ineers, Inc. is needed on ventilationintake pla cement for common HVAC ASHRAE. 1998a. A designer's guide to placement of venti ,�ystems in commercial and institutional buildings such as lation air intake louvers. ASHRAE' Research Project rooftop units, through-the-wall, and at-grade louvers. 806, Final Report. Atlanta : American Society of Heat Althoughsome researchon the effects of exhausts and intakes ing, Refrigerating and Air-Conditioning Engineers, Inc. through building walls has been done, the models used for ASHRAE. 1998b. Design criteria for building ventilation design (ASHRAE 1997a) are based on the industrial-type, inlets: Literature report. ASHRAE Research Project rooftopexhausts, andfume hoods . There is potentialfor devel 806, Final Report. Atlanta : American Society of Heat oping models specifically forthrough-the-wall exhausts and ing, Refrigeratingand Air-Conditioning Engineers, Inc. intakes, as well as those at grade. ASHRAE. 1997a. 1997 ASHRAE handbook-Fundamen Research is needed on using computationalfluid dynam tals. Atlanta : American Society of Heating, Refrigerat ics to simulate the flow around, into, and out of a planned ing and Air-Conditioning Engineers, Inc. building. As computing power increases, it be possible, will ASHRAE. l 997b. Final project report: Influence of architec forexample , to include any nearby structuresand visualize the tural screens on rooftop HVAC equipment. Atlanta : flow between potential exhausts and intakes in everyday American Society of Heating, Refrigerating and Air design problems. Untilthen, designers should use the methods ConditioningEngine ers, Inc. presented in localbuilding codes, the "AirflowAround Build ASHRAE. 1992. Design of smoke management systems. ings" chapter, and the "Designer's Guide." Atlanta: American Society of Heating, Refrigerating Sections need be added or expanded in the ASHRAE to and Air-Conditioning Engineers, Inc. Handbook volumes concerning placement of louvers and Barrett, C.F., D.J. Hall, A.C. Simmonds, and R. Harrison. grilles, especially for commercial and institutional building 1979. Wind-tunnel study on topographical effects on ventilation systems. These applications include rooftop units dispersion from a chimney. International Symposium on and through-the-wall, roof, or sidewalk louvers forbuilt-up and the Control of Sulphur and Other Ga seous Emissions, packaged HVAC systems. Also, thenext published revision of April 3, No. 57: Al-Al3. ASHRAE Standard 62 should include better guidance for designersand code officials on intakeand exhaust placement so Halitsky, J. 1963. Gas diffusion near buildings, ASHRAE thatsome indoor air quality problems can be minimized. Tr ansactions 69: 464-484. For furtherinfo rmationon the factorsaff ecting theplace Halitsky, J. 1977. Wake anddispersion models for theEBRII ment of ventilationair inta kes on commercial andinstitutional building complex. Atmospheric Environment 11(7): 577-596. buildings, see "A Designer's Guide to Placement of Ventila tion Air Intake Louvers" (ASHRAE 1998a) and ''Design Houlihan, T.F. 1965. Effect of relative wind on supply air Criteria for Building Ventilation Inlets: Literature Report" systems. ASHRAE Journal 7(7): 28-31. (ASHRAE 1998b). IAPMO. 1997a. Uniform mechanical code, 1997 edition. Walnut, Calif.: International Association of Plumbing AC KNOWLEDGMENTS andMechanica l Officials. This paper is a result of cooperativeresearch between the IAPMO. 1997b. Uniformplumbing code, 1997 edition. Wal American Society of Heating,Refrigera ting and Air-Condi nut, Calif.: International Association of Plumbing and · tioning Engineers, Inc., and the University of Kansas Center Mechanical CodeOfficia ls. forResearch, Inc., through ASHRAERP-806. The supportby Kundsin, R.B. 1988. Architectural design and indoor micro ASHRAE thisof work and guidance by the RP-806 Project bial pollution. New York: Oxford Press. Evaluation Subcommittee of TC 4.3, Ventilation Require Meroney, R.N. 1982. Turbulent diffusion near buildings. ments & Infiltration, are appreciated. The subcommittee Engineering Meteorology. E. J. Plate, ed. Chapter 11, members were Iain S. Walker (Chair), David J. Wilson, and pp. 481-525. MartinLiddament. NFPA. 1996. NFPA 92A, Recommended practice fo r smoke control systems, 1996 edition. Quincy, Mass.: National RE FERENCES Fire Protection Association. ACGIH 1995. Industrial ventilation, A manual of recom Petersen, R.L., and D.J. Wt lson 1989. Analytical vs. wind mended practice, 22nd Ed. Lansing, Mich.: American tunnel determined concentrations due to laboratory Conference of Governmental Industrial Hygienists. exhaust. ASHRAE Tr ansactions 95(2): 729-736. 8 4229 (RP.:S06) �chuyler, G D., and GG Turner 1989. Comparison of wind Wilson, D.J. 1979� Flow patterns over flat-roofed buildings tunnel test results with empirical exhaust dilution fac- and applications to exhaust ·stack design. ASHRAE tors. ASHRAE Tr ansactions 95(2): 737-744. Tr ansactions 85(2): 284-295. Segal, M. 1989. Atmospheric thermal stratification and the Wilson, D.J. 1982. Critical wind spe�ds for maximum position of mechanical ventilation air in�¥S. Building � aust gas reentry from flush vents at roof level and Environment 24(3): 359_243• � iiltakes. ASHRAE Tr ansactions 88(1): 503-513. Wilson, D.J. 1976. Contaminatic;m of air intake� from roof , exhaust vents. ASHRAE Tr ansactions 82(1): 1024-1038. Wilson, D.J. 1984. A design procedure for estimating air Wilson, D.J. 1977. Dilution of exhaust gases from building intake contamination from nearby exhaust vents. surfacevents . ASHRAE Tr ansactions 83(1): 168-176. ASHRAE Tr ansactions 90(1): 136-152. ·: '· .. · r: ·' , ;- ... :, ' · - • 1 1' ,: .. .. ' " •j .:1· : 1:· ·... -· .. ; . . . I ....,:r I I ...... """ • . ·� . r. .. ; , •...... It .. .. . • " 1!1 ;, ...... , ·.r •' .; _, ' t . .. < I 'I 1"t •• Ir r �' (.I ...... , ' I ' ,.'r ' "· ·, \1' ;J •)' I , , 1 � • '� : . ' ,, 4�9 (RP·BOS) 9 ' .