Ventilation and Infiltration
CHAPTER22 VENTILATION AND INFILTRATION
Ventilation Requirements; Types of Ventilation; Driving Mechanisms for Natural Ventilation and Infiltration; Natural Ventilation; lnjiflration and Air Leakage; Air Leakage Sources; Empirical Models,- Infiltration · Measurement
UTDOOR air that flows through a building either in VENTILATION REQUIREMENTS 0 tentionally as ventilation air or unintentionally as The amount of ventilation needed has been debated for infiltration (and exfiltration) is important for two reasons. over a century, and the different rationales developed have led Dilution with outdoor air is a primary means of control of to radicaUy different ventilation standards.1 Consideratio~s indoor air contaminants, and the energy associated with such as the amount of air required to expel exhaled air. heating or cooling thjs outdoor air is a significant, if not a moisture removal from indoor air, and control of carbon major, load on the heating and air-conditioning system. Thus dioxide (C02) were each primary criteria used at different a knowledge of the magnitude of this air flow is needed for times during the nineteenth century. maximum load conditions to properly size equipment, for Current ventilation rates in commercial and residential average conditions to properly estimate average or seasonal buildings are based on a number of research projects carrie_d energy consumpti on, and for minimum conditions to assure out in the 1920's and l930's, including that of Yaglou.'· 5 This proper control of indoor contaminants. In larger buildings, research investigated the ventilation rates required to keep knowledge of ventilation and infiltration flow patterns is also body-generated odors below an acceptable level in rooms with important for assessing ventilation effectiveness, and smoke comfortable levels of temperature and humidity. It was found circulation patterns in the event of fire. This latter need is that the required ventilation rates varied considerably, covered in Chapter 41 of the 1980 SYSTEMS VOLUME. depending on the cleanliness of the subjects and how many Ventilation occurs by two means, natural and forced. were present in the chamber. (See Chapti:r 12.) Researchers Natural ventilation in turn can be classified as infiltration or also found that C02 concentration was not a good indicator controlled natural ventilation. Infiltration is that flow of air of the ventilation rate above 5 L/s (JO cfm) per person; the through cracks, interstices, and unintentional openings due to C02 concentration was almost always lower than expected for the pressure of wind and the buoyancy effect caused by dif· a given ventilation rate. However, below 5 L/s (IO cfm) per ferences between the indoor and outdoor temperatures. Con person the discrepancjes were not so great, and in fact the cur trolled natural ventilation is that which is due to openable rent rationale for the 2.S L/s (S cfm) per person minimum windows and doors. Control is manual. This is an important I outside air requirement is based on C02 concentration. means of ventilation in residences in mild weather when in The amount of C02 produced by an individual depends on filtration is at a minimum. the diet and the activity level. 6 A representative value of C02 Forced ventilation is mandatory in larger buildings where a production by an individual is 0.0055 Lis (0.011 cfm). When minimum amount of outdoor air must be supplied to meet the a steady state is reached in a ventilated space in which no needs of occupants. ASHRAE Ventilation Standard 62-73 1• 2 removal mechanisms for C02 exist other than ventilation, the (or the latest issue) specifies the ventilation required. Past concentration of C02 is given by: l practice has specified a minimum and a recommended C = C + F/Q (1) amount of outdoor air for various activities and conditions. 1 0 The technology of air contaminant measurement now permits where
alternate methods based on assuring that indoor air quality C1 = concentration of C02 inside the space. meets specified conditions. This permits a variation in the C 0 = concentration of C02 outside the space. amount of outdoor air based on the actual requirements of oc F = generation rate of C02 . cupants in the space. The ASHRAE Ventilation Standard2 Q = ventilation rate (outside air only). defines these conditions. Current ASH RAE standards assume that 0.2H'o C02 is an r This chapter focuses on envelope or shell-dominated acceptable limit. Since the outside concentration of C02 is buildings; i. e., residences or small commercial buildings in 0,. 030'/o, the minimum ventilation rate is: which the energy load is determined by the construction and performance of the building envelope. The physical principles 0.25 = «;l.03 + (0.0055 x 100)/Q Q = 2. . s Lis (5 cfm) (2) I discussed herein also apply to large buildings. With large buildings, however, ventilation energy load and indoor air quality conditions depend more on ventilation system design Minimum Outdoor ~ir Supply Rates .than on the performance of the building envelope. These ASHRAE Ventilation Standard 62-73 (or the most current 1 system design requirements are dictated by the processes serv~ revision) • 2 defines l'T)inirnum outdoor air supply rates for ed by the ventilation system and are treated in Chapters 21 various condi1ions. These rates have been arrived at through a and 22 of the 1980 SYSTEMS VOLUME. consensus of experts working in the field. As shown in Eq 2, a minimum rate of 2.5 Lis (5 cff11) per person for sedentary ac The preparation of this chapter is assigned to TC 4.3, Ventilation tivity and normal diets will hold the C02 level in a space Requirements and Infiltration. 0.25% under steady state conditions. While normal healthy 22.1 22.4 CHAPTER22 1981 Fundamentals Handbook
Available data on the NPL in various kinds of buildings arc limited. The NPL in tall buildings has varied from 0.3 to 0.7 13 14 of total building height. 12• • For houses, the NPL is usually above midheight, and a chimney will raise the NPL as COLO WARM outdoor temperature drops. A pressure difference across an actual building wall, divid ed by the pressure difference as determined from Eq 4, is termed the thermal draft coefficient, and depends on tightness of the floor separation· relative to that of the exterior walls . For a building without internal partitions, the whole pressure difference due to stack effect is across the exterior walls (Fig. - 2A). For a building with airtight separations at each floor, ABSOLUTE PRESSURE there can be no air flow between storie.s, so each story acts in dependently, its own stack effect unaffected by that of Fig. 2A Stack Effect Jn a Building with another (Fig. 28). The sum of pressure differences across the No Internal Partition exterior walls at top and bottom of any story equals the stack effect for that story. Th.is is equivalent to the pressure dif ference acting across each floor, and is represented by the I horizontal line at each floor level. The total stack effect for the total building height is the same as for Fig. 2A. COLD I WARM 4 Real multistory h11ildings are odther open inside (Fig. 2A), ,.. nor airtight between stories (Fig. 2B). There are vertical air "'Ol passages, stairwells, elevators, and other service shafts --J.. ~ "' penetrating and permitting air to flow across the floors. Fig. 2C represents a heated building with uniform openings in the J.. z exterior wall, through each floor, and into the vertical shaft at each story. Between floors, the slope of the line representing NEUTRAL PRESSURE - the inside pressure is the same as in Fig. 2A, but there is a LEVEL discontinuity at each floor as in Fig, 2B, representing the ABSOLUTE PRESSURE pressure difference across it. Total stack effect for the Fig. 2B Stack Effect in a Building with Airtight building remains the same, but some of the total pressure dif Separation of Each Story ference is needed to maintain flow through openings in the floors and vertical shafts, so pressure difference across the ex terior wall at any level is less than with no internal flow resistance. As internal resistance increases, the pressure dif ferences across floors and vertical shaft enclosures increase -F-t-i and the pressure differences across the exterior walls decrease. As height and number of stories increase, the total resistance ,.. of the now path through floor openings increases faster than -~,-=f through vertical shafts, so the shafts mainly govern total "' 3 COLD WARM --t- ~ - - In Eq 5, T1 > T0 • If T1 < T0 , tbe ratio T/T0 is inverted. midheight and without significant internal resistance to now. The effects of internal partitions, stairwells, elevator The slopes of lines are functions of densities of indoor and shafts, utility ducts, chimneys, vents, and mechanical supply outdoor air. In Fig. 3, with inside warmer than outside and and exhaust systems complicate analysis in larger buildings. pressure difference due only to thermal forces, the NPL is al Chimneys are openings at or above roof height and they raise midheight, with inflow through lower openings and outflow the NPL, most significantly in small buildings. Exhaust through higher openings. A chimney or mechanical exhaust systems increase the height of the NPL and outdoor air supply shif1s inside pressure line to the left, raising the NPL; an ex systems lower it, when T1 > T0 • cess of outdoor supply air over exhaust would lower it. Fig. Ventilation and Infiltration 22.S FLOW H H H OUT IN INSIDE WINDWARD .... SIDE x w ":c LEEWARD LEEWARD SIDE SIDE FLOW FLOW OUT IN PRE SSURE PRESSURE PRESSURE (a) STACK ACTION ONLY WITH NEUTRAL ( b) WIND ACTION ONLY WITH PRESSURES OF ( c) WIND AND STACK ACTION COMBINED PRESSURE LEVEL AT MID-HEIGHT EQUAL MAGNITUDE ON WINDWARD ANO LEEWARD SIDES Fig. 3 Distribution of Inside and Outside Pressures Over the Height of a Building JB shows pressure differences due to wind alone, with the ef rise buildings has been used to compute an expression for the fect on windward and leeward sides equal but opposite. total infiltration: Fig. 3C represents the cond.ition where wind force of Fig. 3 Q ... ,IQ,, "' 1 + 0.24 (Q,m 1Q ,,j· (7) 38 has just balanced thermal force wi th no pressure d·ifference 1 1 1 at the top windward or bottom leeward side. Total flow is on where Q.,., is the infiltration assigned to the combined actions ly slightly more or less than with wind action alone. Pressure of the wind and stack effects and Q1,., and Q,m1 are the in differences from wind and thermal forces acting singly can be dividual infiltration values due to the larger and smaller added to approximate the combined effect. pressure effects, respectively. Note that the simple quadrature In tall buildings, exfiltration from windward rooms in expression, Eq 6, gives a slightly larger estimate of total in upper stories occurs at low outdoor temperatures even with filtration than does Eq 7. Both results are plotted in Fig. 4. relatively high winds. 14 Pressures due to thermal forces in Whenever mechanical ventilation equipment is in opera winter dominate at entrances to tall buildings. 12 Thus, tion, it will cause internal pressure to shift so that total air thermal forces must be weighed in estimating air flow into tall entering due to infiltration will equal the total amount of air buildings. In low buildings, the terrain and adjacent struc leaving the house. This is illustrated qualitatively in Fig. S for tures have a major effect on wind velocity and therefore on the case of an exhaust fan and a pressure distribution caused relative importance of wind and thermal forces. In two by the stack effect. houses, 15 thermal forces were at least as important as wind If an exhaus t fan is turned on in a one-story house at a time forces corresponding to weather station winds of 6.7 mis (lS of no wind in cold weather, the total air flow out of the house mph), when indoor-outdoor temperature differences were is the sum of the natural exfiltration and exhaust fan flow. 39°C (70 deg F) or greater in one instance, and 11°C (20 deg F) This mu ·t be equal to the amount of air entering the house due or greater in the other. to infil!ration. Thus, the surface pressures are redistributed, If excess outdoor air is supplied uniformly to each story, the NPL rises, and the new pressure distribution is as shown the change in the exterior wall pressure difference pattern due in Fig. S. to thermal forces is uniform. With a nonuniform supply of When the NPL rises, the exfiltration that occurred before outdoor air (for example, to one story only), the extent of the fan was turned on decreases. Thus the flow out the pressurization will vary from story to story and will depend 1 . 8 .------~ on internal resistances. Pressurizing all levels uniformly has O--C SHAW-TAMURA little effect on the pressure differences across floors and 0- - -0 QUADRATURE vertical shaft enclosures, but pressurizing individual stories increases the pressure drop across these internal separations. The flow through the building shell is dominated by kinetic energy loss mechanisms, where the flow is proportional to the .,J I"a: 0 a' square root of the pressure difference. Therefore, the total flow caused by adding the pressures from the various sources at any leakage site is the square root of the sum of the squares of the flows caused by each source. The simplest model to compute the total flow from the two sources, then, is to combine the flows using this "square" rule. (6) Fig. 4 Two Representations of Total Infiltration Which where Results from Combining Flows Due to Different Pressure Q.,.1 - infiltration from both wind and stack effects, Lis (cfrn). , ) Sources. Q.,, Is Combined Infiltration, Q,m 1 (Q 1 1 Is Flow Q.,. - infiltration rrorn the wind, Lis (crm). Resulting from Smaller (Larger) of Two Pressure Sources. Q, - infiltration from the stack effect, L/s (crm). Note that Total Infiltration Is Less Than Sum of Two A computer model 16 which calculates infiltration in high- Individual Flows 22.6 CHAPTER22 1981 Fundamentals Handbook Building air inlets at lower levels should be larger than the combined throat areas of al! roof ventilators. Natural draft, or gravity, roof ventilators may be sta tionary, pivoting or oscillating, and rotating. Selection criteria are: ruggedness; corrosion-resistance; storm-proofing features; dampers and operating mechanisms; possibility of noise; original cost; and maintenance. Natural ventilators can supplement power-driven supply fans; the motors need only be energized when the natural exhaust capacity is too low. Gravity ventilators may have manual dampers or dampers controlled by thermostat or wind velocity. Stacks or vertical flues should be located where wind can act on them from any direction. Without wind, the chimney effect alone removes air from the room with the inlets. Required Flow The ventilation flow needed to remove a given amount of NO WIND heat from a building can be calculated from Eq 8 if the quan tity of heat to be removed and the average indoor-outdoor Fig. S Surface Pressure Distribution on House in Winter 18 When Both Stack Effect Is Present and Interior Exhaust Fan temperature difference are known. Is Operating, but There Is No Wind (8) mechanical exhaust comes partly from increased infiltration and partly from decreased exfiltration. If the leaks in the where structure are of uniform size and uniformly distributed, only Q = air removed, Lis (cfrn). half of the exhaust system flow would contribute to increased H = heat removed, W (Btu/h). infiltration. Measurements of infiltration induced by residen CP =specific heat of air at constant pressure, 1025 J/kg · K tial combustion systems which draw combustion air from the (0.245 Btu/ lb · F). conditioned space show that on the average 7011/o of the ex Q = density of standard air, 1.2 kg/m3 (0.075 lb/ft3). 17 haust flow is made up by inore-ased infiltration. I; - t 0 =average indoor-outdoor temperature difference, °C (deg F). NATURAL VENTILATION c = 1.23 (1.1). Natural or passive ventilation occurs because of wind and Flow Due to Wind thermal forces which produce a flow of outdoor air through Factors affecting ventilation wind forces include average the various openings in a building. Infiltration is the flow velocity, prevailing direction, seasonal and daily variation in through the unintentional openings. Flow of outdoor air velocity and direction, and local obstructions such as nearby through openable windows, doors, and other controllable buildings, hills, trees, and shrubbery. openings can be effectively used for both temperature and Wind velocities are usually lower in summer than in winter; contaminate control. Temperature control by natural ventila frequency from various directions differs in summer and tion conserves energy and is particularly effective in mild winter. There are relatively few places where velocity falls climates. The arrangement, location, and control of ven below half the average for more than a few hours a month. tilating openings um be designed to combine the driving Thus, natural ventilating systems are often designed for wind forces of wind and temperature. velocities ofhalf the average seasonal velocity. Eq 9 shows the quantity of air forced through ventilation Natural Ventilation Openings in.let openings by wind, or determines the proper size of open Types of openings include: (I) windows, doors, monitor ings to produce given air now rates: openjngs, and skylights; (2) roof ventilators; (3) stacks con necting to regist·ers; and (4) specially designed inlet or outlet Q = c. Av (9) openings. where Windows. Windows transmit light and provide ventilating Q = air flow, Lis (cfm). area when open. They may open by sliding vertically or A = free area of inlet openings, m2 (ft2 ). horizontally; by tilting on horizontal pivots at or near the v =wind velocity, m/s(mph). center; or by swinging on pivots at the top, bottom, or side. c. = effectiveness of openings (C. should be taken as 0.50 to 0.60 Air flow per unit area of opening is identical. Type of pivoting for perpendicular winds, and 0.25 to 0.35 for diagonal winds). is an important consideration for weather protection. Roof Ventilarors. A roof ventilator provides a weather Inlets should face directly into the prevailing wind direc proof air outlet. Its capacity depends on its location on the tion. If they are not advantageously placed, now will be less roof; the resistance it and the ductwork offer to air flow; its than that from the equation; if unusually well-placed, flow ability to use kinetic wind energy to induce flow by centrifugal will be slightly more. Desirable outlet locations are: (I) on the or ejector action; and the height of the draft. leeward side of the building directly opposite the inlet; (2) on A roof ventilator should be positioned so that it receives the the roof, in the low pressure area caused by the jump of the full, unrestricted wind. Turbulen e created by surrounding wind; (3) on the sides adjacent to the windward face where obstructions including higher adjacent buildings will impair a !ow pressure areas occur: (4) in a monitor on the leeward side; ventilator's ejector action. The ventilator inlet should be con (5) in roof ventilators; or (6) by stacks. ical or bell mounted lo give a high flow coefficient. The open ing area at the inlet should be increased if screens. grilles, or Flow Due to Thermal Forces other structural members cause flow resistance. If there is no signifi~~nt building internal resistance, and Ventilation and Infiltration 22.7 assuming indoor and outdoor temperatures are close to 40 26.7°C (80 F), the flow due to sta ck effect is: Q =CAI./ h (1 - t )/t (10) ~--- 1 0 1 /"' where 30 ~ Q =air flow, L/s (cfm). 1-z 2 2 .... // A = free area of inlets o r outlets (assumed equal), rn (ft ) . 0 .h = height from inlets to outlets .• m (ft). ....a:: t; = average temperature of indoor air in height h, °C (F). "- I ~ 20 t = temperature of outdoor air, °C (F). , 0 .... C = constant of proportionality, 116 (9.4), im;luding a value of ~ 65<7/o for effe<: tivencss of openings. This should be reduced to a:: ' (.) SOOJo if conditions are not favorable [C = 89 (7 .2)). z - 10 I Eq 10 applies when 11 > t0 • If t/< t0 , replace 11 in denominator with t0 • I Greatest flow per unit area of openings is ob tained when I inlets and outlets are equal; Eqs 9 and 10 are based on their 0 equality. Increasing the outlet area over inlet area, or vice l 2 3 4 ~ 6 versa, will increase air flow but not in proportion to the added RATIO OF OUTLET TO INLET OR VICE-VERSA area . When openings are unequal, use the smaller area in the Fig. 6 Increase in Flow Caused by Excess of One equations, and add the increase, as determined from Fig. 6. Opening Over Another Natural Ventilation Rules Several general rules should be observed in designing for tions by connecting a suitable fan and flow measurement sec natural ventilation: tion to the building. The building is either pressurized or 1. Systems using natural ventilation should be designed for depressurized and flow is measured as a function of pressure effective ventilation regardless of wind direction. There must difference between inside and outside. Typical lea kage rates be adequate ventilation when the wind does not come from are 8 to 15 air changes per hour at 50 Pa (0.2 in. H 2 0) the prevailing direction. pressure difference. The Swedish building standard is three air 19 2. Inlet openings should not be obstructed by buildings, changes per hour at 50 Pa. trees, signboards, or indoor partitions. Infiltration is caused by the pressure forces discussed in the 3. Greatest flow per uni.t area of total opening is obtained section Driving Mechanisms. Procedures for relating leakage by using inlet and outlet openings of nearly equal areas. to infiltration are included in the discussion of each calcula 4. The neutral pressure level tends to move to the level of tion method. any single opening, with a resulting reduction in pressure Air Leakage Sites across the opening. Two openings on opposite sides of a space will tend to increase the ventilation flow. If the openings are A knowledge of where and how big the air leaks are is very at the same level and near the ceiling, much of the flow may useful in controlling infiltration. Leakage openings can also bypass the occupied level and be ineffective in diluting con cause moisture problems (see Chapter 21). Leakage sites in taminants at the occupied level. American houses that have been measured during weatheriza 5. There must be vertical distance between openings for tion projects are (percentages show the range and average 20 temperature difference to produce natural ventilation; the values for the relative amount of leakage): greater the vertical distance, the greater the ventilation. 1. Walls (1 8-50%; 350Jo). Both interior and ex terior walls con 6. Openings in the vicinity of the NPL are least effective tribute lo the leakage of the structure. Leakage between the sill plate for ventilation. and the foundation, cracks remaining below the bottom of the gyp 7. Openings with areas much larger than calculated are sum wall board, electrical outlets, plumbing penetrations, and leaks sometimes desirable when anticipating increased occupancy into the attic at the top plates of walls all occur. Since interior walls or very hot weather. The openings should be accessible to and are not filled with insulation, open paths connecting these walls and the attic permit the walls to behave like heat exchanger fins within the operable by occupants. conditioned living space of the house. 8. When both forces act together, even without in 2. Ceiling Details (3-30%; 1817/o ). Leakage across the top ceiling of terference, resulting air flow is not equal to the two flows the heated space is particularly insidious because it reduces the ef estimated separately. Flow through any opening is propor rectiveness of the insulation on the floor of the attic as well as con tional to the square root of the sum of the pressure differences tributing to infiltration heat loss. Cei ling leakage may reduce the acting on that opening. effectiveness of ceiling insulation. Recessed ligh1ing, plumbing, and electrical penetrations leading to the attic make the ceiling a par ticularly important area to seal. INFILTRATION 3. Heating Sy tem (3- 28 0/o; ISCIJo). Such items as (a) location of the rur.nacc or ductwork in conditioned or uncondilioned space, (b) use or Infiltration is the uncontrolled flow of air through openings electric or fuel-burning furnace, and (c) presence or absence of in the building envelope driven by pressure differences across outdoor combustion and makeup air all affect total leakage. Duct the shell. The terms infiltration and air leakage are sometimes leakage in an unconditioned space (crawl spa e or attic) is or1en the ai r used synonymously but are different, though related, quan which has just been heated (cooled) by the furnace (ai r conditioner). tities. Infiltration is balanced by an equal amount of ex filtra 4. Windo ws and Doors (&-220/o ; 15 %). The generic window type tion since, except for transient conditions, there is no net rather than manufacturer is the most important determinant in the storage of air in a building. Air leakage is the sum of all leakage of a window (Table 4). Windows which seal by compressing the wea therstrip (casement , awnings) show significantly lower leak parallel air flows through cracks and other openings into or age than windows with sliding sen ls. out of a building without regard to flow direction. 5. Fireplaces (0-30% ; 12%). Fireplaces are inefficient because ex The air leakage rate describes the relative tightness of a cess combustion air is drawn from the room and escapes up the building. The rate can be measured under standardized condi- chimney. When the fireplace is not in use, poorly fitting dampers .._"(.:·.:·- ...... y -~~-·-· - . 22.8 CHAPTER22 1981 Fundamentals Handbook allow air to escape. Glass doors are useful for reducing excess air while Table 2 Air Changes per Hour Occunlng Under Average a fire is burning but rarely seal the fireplace structure more tightly Conditions In Residences, Exclusive of Air Provided for than a closed damper. Chimney caps or fireplace plugs with "tell Ventilation t8Ies" warn that they are in place and are most effective in reducing leakage through a cold fireplace. Single Glass, No Storm Sash or 6. Vents in Conditioned Spaces (2-12%; 50fo). Vents in conditioned Kind of room Weatherstrip Weatherstrlppeil spaces frequently have no dampers or dampers which do not close No windows or exterior doors 0.5 0.3 properly. Windows or exterior doors on 7. Diffusion through Walls (<1%). Infiltration is dominated by one side 0.7 flow through holes and other openings in the structure. By com Windows or exterior doors on parison, diffusion is not an important flow mechanism. two sides 1.5 Measurements of the permeability of building materials at 5 Pa or Windows or exterior doors on 0.02 in. H 2 0 (a relatively large pressure for infiltration) produced an three sides 2 1.3 air exchange rate of less than 0.01 air changes per hour by wall diffu Entrance halls 2 l.3 sion in a typical house. The flow through holes in the structure dominates. with a small window will have a lower air exchange rate than a Other Construction Details small room with a large window. The data in Table 2 apply to A continuous plastic film vapor barrier on the warm side of average residential conditions. Large rooms, high ceilings, ex the insulation is one of the most effective means of reducing cessive glass, etc., will cause departures from these estimates. air leakage through walls and around window and door Calculations by the air change method have been compared frames. Builders frequently install the plastic film on the with tracer gas measurements for two California houses and inside of the studding in frame houses; during construction two Minnesota houses. 26 The comparison indicated the air the film also covers the window frames. Gypsum wall board is change method can give estimates within 20% of placed over the plastic vapor barrier. Trim at the window measurements for average construction under average frames completes the seal at the frame. The plastic covering conditions. Differences of 50 to 1000/o occur for extra tight the windows is removed after the trim is in place. Installed in houses, for houses where furnace ducts are outside the this way, the plastic film produces a continuous film that seals conditioned space, or for unusual wind conditions. Thus the both the wall and the crack around the window frame. It also air change method should be considered a gross estimate at protects the window during construction. best. Plastic vapor barriers installed in the ceiling should have a Crack Method. The crack method calculates the flow tight seal with the outside walls and should be continuous over produced by the pressure difference acting on each leakage the partition walls. A seal is needed at the top of partition path or building component. The flow is given by: walls to prevent leakage into the attic; a plate on top of the (11) studs generally gives a poor seal. Chapter 21 provides addi tional information on vapor barriers (retarders). where It is generally desirable to make a building as tight as possi Q =volume flow rate of air, Lis (cfm). ble and to provide mechanical ventilation with heat recovery, C = flow coefficient, volumetric now rate per unit length of crack, thus minimizing energy consumption and the amount of ven or unit area, at a unit pressure difference. tilation needed. The Nordic countries have pioneered this ap AP= pressure difference. n = now exponent, between 0.5 and 1, usually near 0.65 for proach. Continuous vapor barriers are installed with carefully leakage openings. sealed joints at intersections of external walls and floors, all walls and attic floors, joints around window and door frames, Pressure difference caused by thermal forces is found from and service penetrations. Exhaust fans and air intake slots Eq 4, corrected for the character of interior separations. above windows provide constant ventilation independent of Pressure difference due to wind is the difference between the weather. outside pressure and inside. Inside pressure depends on the ratio of inlet and outlet area which can change with wind Calculating Air Leakage (Infiltration) direction. Pressure difference across the windward wall is: Most of the models used for estimating infiltration are actually air leakage models. Assumptions must be made as to (12) which parts of the building are subject to infiltration and which are subject to exfiltration in order to convert leakage calculations to infiltration estimates. Several techniques have where been used for doing this. P = wind pressure. Air Change Method. The air change method for estimating A = leakage area. infiltration is based on past experience. It applies to average n = flow exponent. residential constf\ICtion under average weather conditions. Subscripts Table 2 presents the number of air changes per hour to be w =windward. expected in rooms with varying exposures. These are air i =inside. leakage rates. L =leeward. The infiltration rates for average buildings under average conditions can be assumed to be one-half the values given in For example, for a square building with leakage openings 1 21 26 Table 2. s. • The procedure for using Table 2 is to multiply uniformly distributed, the pressure difference across the the volume of each room by the appropriate air change rate. windward wall for a quartering wind (at 45 degrees to the The sum of all of the leakage rates is then divided by the total wall) (A ..,!AL = I) is 500/o of the difference between the wind building volume to get the building leakage rate in air changes ward and leeward pressures. For the same building with wind per hour. This total may then be divided by two to get the normal to one face of the building (A,.IAL = 1/3) with estimated infiltration rate. n = 0.65, it is 850fo o( the difference between the windward The air exchange method has a size effect. A large room and leeward pressures. Ventilation and Infiltration 22.9 Table 3 Infiltration Through Double-Hung Wood filtration rates and air flow patterns can be determined for Windows various conditions of wind and outside temperature and 27 (L/s • m (cfh/ ft) of crack) operation of the air handling systems. Pressure Difference, Infiltration by thermal forces comprises the major portion P• (In. H10) of infiltration for a multistory building in cold weather. For a building with a constant cross-sectional area and uniform 25 50 75 18 Type of Window (0.10) (0.20) (0.30) distribution of openings with height, total air infiltration is: A. Wood Double-Hung Window (BHr +- • (Locked) (13) I. Nonweatherstripped, loose fit•,b 2.0 3.1 3.9 n+l or weatherstripped, loose fit (77) (122) (ISO) 2. Nonweatherstripped, average lit 0.7 .• I. I l.S (27) (43) (57) where 3. Weatherstripped, average fit 0.36 0.59 0.77 Q = total infiltration rate, L/s (cfm). (14) (23) (30) 2 1 C = flow coefficient, L/s · m • (Pa)" [cfm/ft • (iii. H20)"]. B. Frame-Wall Leakage< S = perimeter of the building, m (ft). (Leak.age is that passing bc1wccn y = ratio of actual to theoretical pressure difference (thermal the frame of a wood double-hung draft coefficient). window and the wall) P = atmospheric pressure kPa (psi). I. Around frame in masonry wall, 0.43 0.67 0.88 T absolute temperature outside, K (R). not caulked (17) (26) (34) 0 = 2. Around frame in masonry wall, 0.08 0.13 0.15 T1 = absolute temperature inside, K (R). caulked (3) (5) (6) H = building height, m (ft). 3. Around frame in wood frame 0 .34 0.54 0.75 n = flow exponent. wall (13) (21) (29) B = ratio of height of neutral pressure level to building height. •A 2.4-mm (0.094-in.) crack and clearance represent'a poorly fitted window, much poorer CF = 0.0342 (0.52). than average . Infiltration should be calculated separately for exterior l>nte Iii of the average double-hung wood window was determined as 1.6-mm (0.0625- in.) crock ond 1.2-mm (0.Q.17-in.) clcornncc by measurements on • pproxlmatoly 600 windows walls of the ground floor, since its leakage tends to be higher under hcatlog. seiuon conditions. than the other floors. Suggested values of C and n for exterior Table 4 Window and Door Specifications hang-on window, 1.6-mm (0.0625-in.) crack and 0.8-mm Air Leakage• (0.03125-in.) clearance, equals that of a loose-fit, double. hung wood sash window, not weatherstripped. leakage rate Specification/Material [At 75 Pa (0.3 In. H2 0) Unless Noted) of openable aluminum storm windows depends on fit and if weatherstripped or not, but may be estimated from Table 4. ANSI A/34./ (Windows, Aluminum) A-Al (Awning), 0.77 Lis· m crack Leakage rate of the storm unit of a double window is usually C-BI, C-A2, C-A3 (Casement) (0.SO cfm/ft crack) about the same as that of the prime unit, but leakage through DH-Al, DH-A3, DH-A4 (Hung) the combination depends on their individual leakage HS-AJ (Sliding) characteristics. Leakage of the combination in terms of the P-BI, P-A2 (Projected) leakage of the prime window alone, assuming the flow ex VP-A3 (Pivoted) ponent n, is equal for the prime and storm window, as: A-Bl (Awning) 1.16 Lis · m crack DH-Bl (Hung) (0. 75 cfm/ft crack) (14) HS-BI, HS-B2, HS-A2 (Sliding) JA-BI, (Jai-Awning) VS-Bl (Vertical, Sliding) where Qc "' now rate for combined prime and storm window. J-BI (Jalousie) 7.62 Lis· m2 Q = now rate for prime window. (I .SO cfm/ftl) S: = proportionality constant for prime window. c.:, = proportionality constant for storm window. P-A2.50 (Projected) 0.58 Lis · m crack For n = 0.65, leakage through a combination whose storm TH-A2 (lnswing) (0.375 cfm/ft crack) unit has the same leakage characteristic as the prime is about VP-A2 (Pivoted) 350'/o less than that through the prime alone. By applying tight P-A3 (Projected)b 1.16 Lis · m crackb TH-A3 (Inswing) (0. 75 cfm/ft crack) storm window units to poorly fitted windows, leakage may be VP-A3 (Pivoted) reduced 500Jo, roughly equivalent to weatherstrips. Air Leakage Through Walls ANSI A 134.2 (Sliding Glass Door, Aluminum) 5 SGD-Bl 5.08 Lis · ml Infiltration data through brick and frame walls32-l are in (1.0 cfm/ft2) Table 3. Plastering reduces leakage about 96%; a heavy coat of cold water paint, 50%; and three coats of oil paint SGD-82, SGD-A2 2.54 Lis· m2 carefully applied , 280Jo. Table 3 shows that infiltration SGD-AJb (0.50 cfm/ftl) through properly plastered walls can be neglected. The value of building paper applied between sheathing and ANSIA200.l shingles is shown by curve 30-70, Fig. 7, for outside con All Types Wood Windows , 0.77L/s · m Class A& B (0.50 cfm/ft) struction without lath and plaster. Standards of the National Association of Architectural Metal Manufacturers call fo.r 2 2 ANSIA200.2 maximum leakage of0.3 Lis · m (0.06 cfm/ft ) at a pressure All Types Sliding Glass 2.54 Lis· ml difference of 75 Pa (0.3 in. H 20) through curtain wall Doors, Wood (0.50 cfm/ftl) specimens, exclusive of leakage through operable windows. The corresponding flow coefficient, C, assuming a flow Fed. MHC & SS< 280.403 All Types Windows and 2.54 Lis· m2 Sliding Glass Doors (0.50 cfm/ft2) N • i ELEVATOR SHAFT Fed. MHC & SS< 280.405 5.08 Lis· m2 5 NOS l,!t - CA~f · t N · D \, A ~f CO~ CA t fE NOS 2,7- CA S t- 1N ~ P\. " t:'[ C0Htf:IE.J ( , [ .:t((PT All Types Vertical Entrance (1.0cfm/ft2) \60 FROl'f f 0, (OHCfoi( rr 61..0.(JC •o NO I- CAS T-IN• PLAC ( ( O ~ CREf(,CCC:tPT a At 75 Pa (0.30 in. H10) pressure or 11.2 mis (2S mph) wind velocity. TWO S10£S 0 1· co1.c 11 et( 81,. 0(M, b At 300 Pa (I .20 in. H 0) pressure or 22.3 m/s (SO mph) wind velocity. NO 4 - CONCR£TE BLOCM. 2 o•O NO 6 - CLAY TILE BLOCIC: CFederal Mobile Home Construction and Safety Standard. •20 ~ 0 . 45 ~-~~-~~--~-~~~-·-~~~~ J: ~ o. .c o 20 I 100 0 .35 :i ; 0 .30 80 J: CJ 0.25 " 0 "a: ...J: 0.20 60 .. 0 . 15 •0 0 a: CONVERSION FACTORS: 0 w 0.10 /f'-----i L/1•m2 ::: CFH/fT2 X 0 .086 •O a: Pa::: In. H20 )( 248 mm = kl. X 215 .4 :" 0 O& .. 00 a: 20 .. 00 20 •o eo eo 100 120 uo 100 1eo 200 220 2•0 2eo 2eo Joo INFU.. TRATION. CFH PER SO.FT Of WAll o JD-70: J-0-l~~n. shlo;clc:,. on 1 ~ 4 · 1n . boards on 5·1 n. rc- nttn wllh 0 010 020 OJO 040 o~o 01)0 1NCHES OF Wo\TER poptr, 7-D-1 6·1n. shlnii).,, shlplap and pl p Table5 Air Leakaae Throuab Walls to an orifice of 0.14 m1 (l .S ft2), or about 0.33m2 I1000 m1 (1 (L/1 • m1 (cfb/ft1)J ft2110 ()()() ftl) of house volume. Leakage flow through storm Pressure Dlffereace, Pa (la. HzO) windows and doors was about 20% with the remainder through walls and ceilings. A pressure difference of 15 Pa (0.3 Tye!ofWaU 12 (0.05) 25(0.10) $0 (0.28) 75 (0.30) 2 in. H 20) produced leakage rates of: 1.4 to 4.8 Lis · m (16 to Brick Wall: 8.S in. S1 cfhlft1) through the ceiling; 3.4 to 5.9 Lis · m1 (40 to 70 Plain 0.42 0.76 l.3S 2.03 2 (S) (9) (16) (24) cfh/ft ) through frame walls with brick veneer or metal siding; 0.8 to 1.0 Lis · m1 (9 to 12 cfhlft2) through stucco Plastered 0.004 0.007 0.012 0.017 finish walls. Two coats on brick (0.05) (0.08) (0.14) (0 . 20~ Table 5 shows that a frame wall would have a leakage rate 1 1 Brick Wall: 13 in. of 0.02S Lis . m (0.29 cfhlft ) at 75 Pa (0.3 in. H 20) Plain 0.42 0.68 1.18 1.69 pressure difference. Thus, in-place wall leakage is sub (S) (8) .. (14) (20) stantially greater than laboratory measurements. Plastered 0.001 0.004 0.004 0.008 Two coats on brick (0.01) (0.04) (O.OS) (0.09) Air Leakage Through Walls of Elevator and Stair Shafts Plastered, Furrin8, Lath 0.003 0.020 0.039 O.OS6 Two coats gypsum (0.03) (0.24) (0.46) (0.66) Elevator and stair shafts, floor construction, interior parti Plaster tions, and service shafts are major separations in a buildjng. Frame Wall: Because they provide internal resistance to air flow, their air Bevel siding painted 0.008 0.013 0.019 O.o2S leakage characteristics are needed to determine infiltration or cedar singles, through outside walls and the air flow pattern with.in a sheathing, building (0.09) (O.lS) (0.22) (0.29) building. ln cold weather, most upward air flow is inside ver paper, wood lath, and three coats tical shafts, the least resistance path from floor to floor and gypsum [!laster the main avenue for transfer of odors and air contaminants. In case of fire, measures to prevent smoke contamination of elevator and stair shafts used for evacuation and fire exponent of 0.65, is 0.018 Lis · m2 • Pa (0.13 cfmlft2 • in. fighting are essential (see Chapter 41, 1980 SYSTEMS H2 0). Based on measured leakage of eight multistory office VOLUME) . buildings with sealed windows and spandrel panels of precast 2 Pressurization is one means of maintaining a shaft concrete or steel, s flow coefficients for tight, average, and habitable during a fire. Pressure inside the shaft is increased loose walls (depending mainly on joint design and work above adjacent floor spaces by forcing outdoor air into the manship) can be assumed as 0 .03, 0.09, and 0. 18 (0.22, 0.66, shaft by a fan. Air flow direction is from shaft to floor and. J .30), respectively. These values can be used in Eq 11 or spaces, and smoke from a fire is impeded from entering the 13 for calculating curtain wall infiltration rates. 13 shaft. Air supplied to the shaft also dilutes smoke, which may Measured leakage of a nine-story building with masonry have migrated into the shaft prior to pressurization or when walls and operable aluminum sash windows was 9.84 several shaft doors are opened during evacuation and Lis . ml (l .90 cfmlft2) of outside wall area. For an assumed firefighting. leakage of 2.32 Lis · m (l .50 cfml ft) of sash crack at 75 Pa For design of stair shaft pressurization systems, informa (0.3 in . H 0) pressure difference, the windows and doors 2 tion on both airtightness of shaft walls and the pres ure loss contributed about one-fourth of the total, with the remainder characteristic is required. Flow resistance of the channel through the wall. formed by the staircase and walls has a significant effect on Recent studies36 on houses with a pressurization fan in vertical distribution of pressurization. dicated that typical total leakage area was almost equivalent 51AlRSHAFT 0: NOS r,2,3, .. ,6 - CAST· IN· PLACE CONCRETE,PARG(O 0 a: .. 0 0 ~: FLOW RATES AT PRESSURE DIFFERENCE ACROSS DOOR tdPI ... NO 5- CAST·IN-PLACE CONCRETE, PARGEO EXCEPT 0 0 "'• 0 OF 0 lO INCH OF WATER { 75 N/ m2) ~ F~ONT AND BACK OF CONCRETE BLOCK A ' FOR OTHER 6.P, MULTIPLY LEAl 0: CL.IE\ 0 .40 O.H v"" J 0 ...... O ·~ ,.,,,.. 0 .32 ,...... c\f..-;,. ~ v ~~/" ,_ '- o:!t cO~ Pl 1- .... 0 .28 @ z © ~~/ ..... v o:!>~ ... & ...... ~ 0 .24 "'~ ...... v v v o .i~ v ,v ...... v ..... _...... "'8 0.20 ,,.... ~ ~ I'~ I/"' v L- v ,....0 '.io l-- u ..~ v v ...... _i- "': 0. 16 I(, • ~ _.... •;/~'!::,,. v,v - _..... II: v c.. '- .... v .... /, v 1_.....v _...... d~ ~ 0. 12 . v v ES'l'l 61JL!,_ TY PE v (....- ...... ' -...... _ [/ I// , v i- ...... OJS!.... L- 0.08 [...... ,_ , "" v --- f/ I / ... '-- i.-- ..... I-I- ,, _v JV v ,_ ...... L-- ... o. ~ 0 .04 ., _..... / ~ - I/ I/ I 0 - 0 o 100 200 300 400 ~oo 600 roo 800 900 1000 TRAFFIC RATE - NO . OF PERSONS /(HR)(DOOR) 2 .0 I / / / / I / / / ""~ ,t,' / I/ / I / I/ i/ !/'/ 4& . ~ I J 1.8 I J v / ,___ / I J J I / '/ Air lea ka.ge through elevator shaftsJ., occurs through open D, =equivalent diameter, m ~t) . ings in walls, doors, and at the top of shafts for vents, car VP =velocity pressure, Palm (in . H 2 0). cables , and other elevator accessories. Leakage ra res through The pressure loss coefficient K is analogou to duct friction shaft walls and wall openings are given in Fig. 8. factor/. Equivalent diame ter can be calculated: Leakage openi ngs at the top of an elevator sha ft are D, 4A/P (16) equivalent to orifice areas from 0.37 to 0.93 m 2 (4 to 10 ft 2) . = Air leakage rates of elevator ancl stair doors 37 are given in where Fig. 9. For an open elevator door with the car in place, it can A = inside horizontal cross-sectional area of shaft, m2 (ft2). be assumed leakage is equi valent to a 0.56-rn 2 (6-ft 2) orifice. P = outer perimeter of the insi de horizontal cross section of shaft, Air leakage rates through the stair shaft walls are in Fig. 10, m (ft). and a re similar l-O those of cast-in-place elevator shafts. Varia The velocity pressure of the flow of air at standard condition tion in the ai1 leakage rates shown in Fig. 10 is probably due can be expressed: to workmanship in sealing openings. Pressure losses inside a stair shaft can be calculated by con (17) sidering it a rectangular air duct: where APL = (KL Vp)l(D,) (15) Q = flow ra te, Lis (cfm). where c = 1.29 (4005). 2 l!PL = total pressure lo per floor, Pa/ m (in. H 2 0). Fi eld tests gave K as 35. This value, compared with air duct K = pressure loss coefficient. fri cti on fa ctor,/, of 0.01 lo 0.05, indicates now resistance in l = height of shaft per floor, m (ft). stair shafts is several orders greater than that o f air ducts. yentilation and Infiltration 22.13 In contrast to ordinary stair shafts, scissor stairs have two Z40 separate staircases in one shaft. Thus, half the cross-sectional area should be used to determine velocity pressure. The value ~- ~I.-- ...... of Kis approximately 15. l'~c."' 1J't it>);;- ...- Air Leakage through Exterior Doors [....-" v- Door infiltration depends on the type of door, room, and v building. For residences and small buildings where doors are ,__ /" ~ used infrequently, infiltration can be estimated on the basis of Rll.Cll air leakage through cracks between door and frame. Door fit v I /~ varies greatly and is affected by warping. For a well-fitted , /~ i--- I I door, leakage approximates a poorly fitted double-hung win i,..- ...... 11 6 1 N .t R~ CK J - dow; for a poorly fitted door, the figure may be doubled. If ,/ I '-- the door is weatherstripped, the values· may be halved. A ...... -- 0 ~ frequently-opened single door, as in a small retail store, may 0 0 .2 o.4 o .6 o~ 1.0 12 1.4 .. 6 1.e have a value three or more times that of a well-fitted door as PRESSURE DI FFERENTIAL-INCHES OF WATER an allowance for opening and closing losses. Doors of com Fig. 12 Leakage Rate through Swinging Door Cracks mercial buildings with heavy traffic have high leakage rates. An ASHRAE research program provides comprehensive data on air leakage characteristics of swinging door entrances 12 EMPIRICAL MODELS and revolving doors. 38 Complementary data on pressure dif ferences across entrances of tall buildings are included. 12 Empirical models of infiltration have been generated based on long-term field measurements. The technique uses Swinging Door Entrances measured hourly infiltration rates and weather data to A simplified design chart39 (Fig. 11) can be used to estimate develop different regression models relating the two sets of infiltration through swinging door entrances if building variables. height, inside-outside temperature difference, net outdoor air The simplest of the many regression models has the form supply or exhaust air change, type of entrance, and traffic I~ K, + K 2 At+ K3 v (18) rate are known. Entrance coefficients for summer cooling are essentially the where same as for winter heating.9 Pressure differential data across I= air change rate per hour. the entrance, due to combined temperature difference and fan At= indoor-outdoor temperature difference, °C (deg F). v = wind speed, mis (mph). operation in summer cooling, are not available. A complete K 1, K 2 , K 3 =empirical constants derived from measurements at inversion of pressure difference for winter heating may be the site. assumed for summer cooling: the negative pressure dif ferential (inside pressure greater than outside pressure due to Constants vary significantly from site to site. Care must be heavier inside air) can be determined by Fig. llB. Note that, exercised in using this general regression expression as a in winter heating, exhaust fans raise the pressure differential predictive model of an arbitrary house. Typical values of the constants suitable for different classes of houses are given in at the entrance; while, in summer cooling, they decrease 40 negative pressure differential and exfiltration. The curve for Table 6. net supply in winter heating in Fig. 1 lB becomes the curve for Air Leakage/Infiltration Correlations net exhaust in summer cooling. Entrance exfiltration can then The previous calculation procedures described are simple be evaluated by Figs. 1 lC and 1 lD. but of uncertain precision. Better precision is possible if the Leakage through door cracks (significant only in periods of house condition is explicitly measured and if the weather at very low traffic) can be found from Fig. 12, once the entrance the site rather than the weather for the region is used in the pressure differential is determined from Fig. 11 . calculation. The most straightforward method for measuring Infiltration through revolving doors is influenced by the leakage rate of a house uses fan pressurization. An in movement of the door, leakage past door seals, temperature filtration model which combines the results of air leakage and wind pressure difference between indoors and outdoors, 38 measurements using fan pressurization and weather effects at traffic pattern, and traffic rate. Inside and outside air the house are described below. In this model the infiltration, turbulence and condition of the door seals also have effect. Q, is the larger of two values, Q,,ad: and Qwtnd• in which;41 Leakage through door seals is due to pressure differential across the building entrance and size of openings at the seal. Q.,ad: '"' J; A I VAT (l 9) Revolving the door causes almost equal exchange of indoor Qwlnd • J.,,A, V (20) and outdoor air, which depends on door speed, temperature differential, and somewhat on wind and indoor air velocities. where QJtad: - stack dominated infiltration, L/h (ft 3 /h). A design chart 39 based on an ASHRAE research report 38 .Qwlnd - wind dominated infiltration, L/h (ft1 /h). evaluates infiltration through manually-operated and power · J;.t~~ dimensionless building parameters. operated revolving doors (Fig. 13). Fig. l 3C is for a worn seal 2 A 1 - leakage area of house, m (ft2). which still provides good contact with adjacent surfaces. t..T"' indoor-outdoor temperature difference, °C (F). When further wear reduces contact, leakage increases. v "' measured wind speed, m/s (mph). Table 6 Coerrtcients for Multiple Linear Regression lnflltrallon, Eq 1 Construction Type Description Tight 0.10 0 Oil 0.034 New building where special prccaulions have been 1aken to prevenl infiltration. Medium 0.10 0.017 0.049 Building constructed using conven1ional construction procedures. Loose 0.10 0.023 0.067 Evidence of poor constructi on or older buildings where joints have separated. 22.14 CHAPTER22 1981 Fundamentals Handbook INFILTRATION THROUGH REVOLVING DOOR- CFll 200 400 600 800 1000 IZOO 1800 2000 I 1 I\ II I v~ MOTOR • OPERATED zo,30 71' REVOLVING DOOR a i' oro II: I I I I I l I I I 000 \ \ ). I\ I \ \ \ \ t- AIR FLOW \ \ \ \ \ \ \ AIR rOW I- I 900 \ \ '®I ~ \ I \ I\ \ I\ I\ I ,~- I- \ \ \ \ 0 ' I ' ' I- ' 1\0 800~ \ \ \ ' \ \ \ \ I\ © u I- \ \ \ \ \ $ 00 .,. ' I- TWO WING.$ FOUR WINGS 700~ \ \ I\ \ \ \ ' ' I\., -' \ .... \ \ " "\ \°{, "' ' ' ' 0 600~ ' \ \o-; 'I. f\ ' I\ I\ \ g \ (' ' \I ' ~ - ,, . \ ' \ \ o ~ ..... ~00 .. ' ~~ I\ .. I\ \ "':> I\ \ I\ \ l"\-o.. - ~ ..... 0 {~ 'I ,, ,o- a: ' ' ' - 4DO~ I\ \ ~I ~ I\ I\ I \ ~ - I\ \ TWO WINGS-~ v z 0 ' ' \ :J I' ' I ~ v 1.....- ~ '~ ' ' , v 300~ I\ I\ I\ ~... " l. !~'."":::!'.._ _ l\, ... ~ 1,,,,, I'. - J,~ "'!::; ' ' ·i<: ' ~I ' I/ "-FOUR WINGS ' ' VI 200~ I\ I\ I\ ~~- rs.~ I\ I\ I\ I\ l/ v 17 ' ~ - <'.,_ 'J 'l ' ' ' ' I ..._ ..._ !\\ 0 ~ , I\ I\ I\ I\ I\ I 100 \) \I ~ ' I 0 2 .0 / / / / I , '.I' v ., .f /~4. ti:/ I / /1 I 1.8 I J / v / / I// I(~ &,~ I I ..... - v v ® I/ / / I ' J / I/,/ ~.('/ II I / .."' .;1 / / v / I , v V "I ~ ~"; / I ~ 1.6 ,. .;- i/ ~ ~ ~ / v / / "v'\, / /V / ll~~ _,.,._., J I / ...0 / ,J / 1. 4 / OJ il.'.LL lfe ~...., II I ., ~o~ 0,0 0 I) / ...,v J 1. ... or"'.. ~,:;- ...9 / I/ "' % ~ 17 "' v / ~ 1.2 1 0 / -" iJ I/ o o'!'o -1-.' I /l/,i /[/I/ I [/ I} v I/' I/ rl l / / V O :~ J /II .t , .,cy l/v 0 .. 1.0 J / I I/ j I I ~ J l/V I} · 0~~, v, i/ .'j/ 17 I/ 9 ..-... I/ Iv I/ r;1 , 1fV !/ l/ [J/1, / ·-17 ,_V' ~ ,'7 ...- .. , I/ ir 17 / r1 I/ I/ J -· I/ /l/J ~ 0 .8 I ' ~ ~ v, ·1 IJ, -' I/ v l/ v v"' IX I ' IJ I/II J v ® - .. Vj v v ,~ ..... V II ~ ~ 0 .6 / I/ I/ ' I I/ I/ I/ '/ ... v;, '/ / y""' io i- .... I IJ "' / / v I / I I 'J 0 /, v 1 ~ .' I .."' 0. 4 '//r / / / /1.7 I x W, """",.,,,, ..... -- lj/ ... '/v / 10 I /II v v I/ v,, ~ v"' '--'" ..... -- _i.- - I I '/ 0 .2 .__ I J I/ ~ ;....-- v~ / I - / I • i--..- -- / /I/ 0 / ::::.. v 0 100 200 300 400 500 600 700 800 900 IOOO 0 0 Z 0 4 0 6 08 I 0 1.2 I 4 I 6 I 8 2.0 HEIGHT OF BUILDING, FT EFFECTIVE DRAFT 6PE- INCHES OF WATER Fig. 13 Design Chart for Evalualing Air Leakage Rate through Revolving Doors • ventilation and Infiltration 22.lS Table 7 Terrain Parameters for Standard Terrain Classes Oass a y Descripllon L/h QIAt [ mm2 J= 9.0 1.30 0.10 Ocean or other body of water with at least 5 km (3. I miles) of unrestricted expanse. II 1.00 0.15 Flat terrain with some isolated obstacles (e.g., buildings or trees well separated *~ 7.2 from each other). 2 Ill 0.85 0.20 Rural areas with low buildings, trees, etc. > IV 0.67 0.25 Urban, industrial, or fon:st areas. v 0.47 0.35 Center of large city (e.g., Manha ttan). ~ () uJ ~------5_.4______.,,.,,-::: .. -- -- u.. , - u.. Therefore, the effective leakage area is computed by plotting uJ Q vs. /J.P on log-log graph paper, extracting the flow at AP= 4 0 ..... Pa from the graph and using this in the defining equation (Eq 3.6 - - ~ ------.,,/ - - 17) for the effective leakage area. :: ----ye .,,,,,,.,,,. 1.8 I A A, = V (2 (21) ~.(I ~PIQ) ..! ~ _J-~A I' I I where 2 2 V I I A 1 = effective leakage area, m (ft ). Q ~ I I I Q =flow at measured P, Lis (cfm). 0 1 2 3 M' = measured indoor-outdoor pressure difference, Pa (in. H2 0). 2 Q =air densi ty, kgJm3 (1 .2 at sea level and 294 K) [lb/ft3 (0,075 STACK EFFECT, LH-(t8*) at sea level and 530 R)) . Fig. 14 Lines of Constant Infiltration as a Function of Wind If insufficient data exist to determine the flow at 4 Pa Speed and Temperature Difference. Dashed Line Separates (0.016 in. H 2 0), Eq 21 may be used directly for the lowest Wind-Dominated Regime from Stack-Dominated Regime. pressure-flow measurement available. The building Points A, 8, and C Are Results from Examples 1 and 2 parameters.fwandfs are defined in Eqs 22 and 23. R [ a Infillration for a structure can be determined directly from 3 - (H/ 10) y ] (22) Fig. 14. The wind parameter.J:(Eq 22), which is unique for a f..,= -9- a'(H'llO)y' particular building, is multiplied by the measured wind speed (e.g., from a meteorological station at an airport) to find a where coordinate on the vertical axis. The square of the stack R = ratio of the leakage area in the horizontal surfaces of parameter, ((,)2 (Eq 23), is multiplied by /J. T to find a coor the building to the total leakage area o r the building. dinate on the horizontal axis. The point defined by these coor H = height or the fl oor or the attic of the building, m (ft). dinates determines the infiltration prediction. If lhis point is H' = height of the wind speed measurement, m (ft). above the dashed line, the infiltration is wind dominated, if a, y, a', y' = constants which de line the change of wind speed with 44 below, stack dominated. height in the cxpression: Once the point is located on the graph, the ratio of infiltra v = v a (h/h )Y tion to leakage area is determined by interpolating between 0 0 the lines of constant infiltration drawn on the body of the where vis the wind speed al height h,v0 is the wind speed at graph. In the wind dominated portion of the rigure (above the height h 0 , and a and y are constants defined for terrain classes dashed line) this is simply a linear interpolation between lines listed in Table 7. 2 sepanHcd by 1.8 L/h · mm • In the stack dominated regime, In Eq 18, the primed quantities refer to the terrain class at the interpolation is more difficult because of the quadratic the wind measurement location, the unprimed quantities to spacing of the lines. The simplest procedure is to move ver the terrain class of the house. tically from the point to the dashed line (the locus of points It is important to emphasize that f. and f.,, are building where the infiltration from the stack effect and the wind effect parameters which need to be calculated only once for a arc equal). The linear interpolation in the wind regime then structure. All infiltration results are then related directly to can be used. The number read from the graph is multiplied by measurements of windspeed and temperature difference. The the leakage area of the house to determine the infiltration, stack parameter .fs is given by: L/h. In this model, the leakage area of the building, measured a 2 + R) c H)o.5 (23) single time at the site, is the scale factor that allows the in· .t:• - ( - 9 2g-T filtration to be predicted for many different weather con 42 ditions. Low pressure flow measurements show that a where suitable model for flow in the pressure range characterized by 2 2 infiltration is: g =acceleration of gravity, 9.8 m/s (32.2 rt/s ). H = height of the floor of the attic, m (ft). T = absolute temperature of the interior of the building, K (R). where The constant R is given by, Q = total flow through the building shell. R ""(A, +A )1A, (24) AP~ inside-outside pressure difference. 1 where Field measurements at pressures above 10 Pa show that the A, =leakage area of the ceiling of the living space, m1 (ft2 ). 43 2 exponent of the pressure term is often larger than one-half. A 1 = leakage area of the noor, m (ftl). 22.16 CHAPTER22 1981 Fundamentals Handbook 2 A - total leakage area of the structure, m 2 (ft ). The leakage areas of the floor and ceiUng, A1 and Ac, FURNACE - Cl which are required to compute R, can be determined by (1) 0- ()+ direct measurement, (2) identifying leaks in the ceiling and floors, or (3) assuming uniform leakage and scaling by the I"' surface area (most often used). Examples 1 and 2 compare --o_ calculations by the simple air change method with air leakage I extrapolation and infiltration measurements. The comparison BASEMENT is made for a two-bedroom, single-story frame house in CHIMNEY Ottawa, Ontario, shown in Fig. IS. Example I: Compute the infiltration for the Ontario house shown in Fig. IS using the Air Change method. None of the windows in this house is weatherstripped. Solution: The volume of each room is computed using the dimensions from Fig. IS. The product of the volume of the room and the number of air changes assigned using Table 2 gives an infiltration value. The sum of the infiltration values for all the rooms gives the total infiltration, m3 lh, for the house. Dividing this value by the house volume gives the infiltration rate, air changes per hour. !-+- LIVING ROOM (3,7mX6.3m) Air Changes Infiltration, Room Volume, m1 per Hour m11h Living Room S7 I S7 Kitchen 22 1.S 33 Dining Room 2I 1 21 Bathroom I3 1 13 Bedroom I 2S 1 2S BEDROOM Bedroom2 3S 1 3S Basement I60 1.S 240 t (3,7mX3.9m) Total infiltration: 420 m 3 lh. Volume of house: 337 ml. Predicted leakage rate: 4201337 • 1.3 air changes per hour. Predicted infiltration rate: 1.312 - 0.65 air changes per hour. It must be emphasized that this prediction is an average value, in dependent of any weather condition. FIRST FLOOR Example 2: Air Leakage Extrapolation Model Infiltration rates are --e STATIC PRESSURE TAP to be calculated for: x THERMOCOUPLE (A) t ~ 29.4°C, v 1.4 mis = 45 (B) t = -l.1°C, v = 2.7 mis Fig. 15 Plan View of House No. 1 from Tamura (1979). (C) t = 18.6°C, v = 4.0 mis The House, Located in a Residential Area of Ottawa, of 3 The leakage flow measured at 7.5 Pa was 547 Lis and flow vs. Ontario, Has a Volume 337 m pressure was found to be Q = C (AP)0.6S. Solution: Using this relationship with the flow value at 75 Pa leads 2 + 0.65 to a flow at 4 Pa of: J; = - - \/2(9.8)3. 11293 = o.13 9 0 65 3 (Q)4 = (Q)n (4175) · x 10 = 81 Lis The coordinates for Fig. 14 for the three cases listed are: Therefore, the effective leakage area is 0 ~Tl ( C) v (mis) if.;) v <.t;> 2 - IHI 81 x 1ol 29.4 1.4 0.31 0.53 2 A 1 = = 32000mm I. I 2. 7 0.59 0-02 (2 X 41 1.2)CU 18.6 4.0 0.88 0,33 These values of [({:,) · v] vs. [(/s)2 - I~ arc plotted as points 3 3 2 71J Note: 10 converts m Is to Lis and to mm , respectively. A, B, and C in Fig. 14. Point A in the temperature dominated region is The me.asurements of wall and ceiling leakage gave ceiling leakage projected up to the dashed curve to find a value of QI A 1 = 2.5. This of 65 11/o or the total leakage of the structure. Since the basement was a is multiplied by the measured leakage area of 32 000 mm2 to give a conditioned space, leakage into the basement was considered part of predic ted infil tration n ow rate of 80 000 L/h. When divided by the house volume of 337 m1 the predicted infiltration rate becomes 80 the wa ll leakage. Therefore, A1 is zero. The value of R is 000 >< 10- 11337 "' 0.24 ai r changes per hour. -, R =(Ac+ A )1A = 0.65 1 1 Points B and C are in the wind dominated region. Their values of The wind speeds given are for conditions when measurements were QI A1 are 2. 1 and 3. I rspectively. The infiltration flow rates are 68 000 made at the site on a 7.6 m weather tower. The height of the ceiling and 100 000 L/h, giving infiltration rates of 0.20 and 0.30 air changes (floor of the attic) above grade was 3. 1 m, a nd the houses were judged per hour, respectively. These predictions are compared below with the to be located in terrain class Ill. Therefore a = a• = 0.85; measured infiltration rates: y = y' = 0.20. The expression for .I".,. is now: Case Predicted Measured Q(L/h) 1• l• (0.85 (0.31)0.lOI A = 80000 0.24 0.22 0 0.22 (0.85 (0. 76) ·201 B 68 000 0.20 0.16 c 100000 0.30 0.23 The stack parameter is easier to compute: •Air changes per hour. • Ventilation and Infiltration 22.17 .... 50 E 180 \') a. 38 0 ,... 45 .s .. E Q )( c. 30 140 40 .... ~ ..,c. "'Q E 24 ::i Cl 35 So z 100 w .... 0 .... Cl 18 < E 30 ~c CONVERSION FACTOR: a: ....a: 12 cfm= Llh X (1/1700) 80 ~ z z 0 25 w ..J Q 0 8 ...... z 20 a: < 0 a: 0 0 0 < ..... 20 0 20 40 80 80 100 120 140 180 180 z .• w TIME, MINUTES () z 0 15 Fig. 17 Infiltration Measurement by Constant Tracer Flow () Method < (!)"' space, F, and the tracer gas leaving the space due to ex fil tration, Qc: V(dcldf) = F- Qc (25) 20 40 60 60 100 120 140 where TIME, MINUTES c = tracer concentration. Fig. 16 Tracer Gas Concentration vs. Time. Points V =space volume containing tracer gas, m1 (ftl). Represent Three Consecutive Decays Separated by Rapid F = tracer injeotion rate, Lis (cfm). Injections of Tracer Gas. Slopes or Straight Lines Give Air Q = ex filtration (or infi!Lration), Lis (cfm). lnfillralion Rates: In T his Case 1.02, 1.06, and 1.07 Either a tracer decay method or a constant flow method may Air Changes per Hour, Respectively be used. These predictions arc seen Lo agree wi1h measurements much better Tracer Decay Method 1hen the simple air change method (0.65 air changes per hour). The T~e Tracer Decay method is the most common and requires Air Leakage Extrapolation method does, however, require on-site mea uremcnts. Thus it is less auractivc ror routine use. the simplest apparatus. Tracer gas is initially i.njecte 22.18 CHAPTER22 1981 Fundamentals Handbook PRESSURE, in. H20 If the tracer is added at a constant measured flow rate for a -0.3-0.2-0.1 0 0.1 0.2 0.3 measured time .interval, the effective volume of the space can be calculated from the initial concentration at the end of the charging period. t7 4000 2000 (30) 3000 ~· 1500 0 /I where 0 2000 " 0 ~ 1000 Vs = space volume, m1 (ft3). ~ F = tracer gas flow rate, L/h (cfm). x 1000 I E c = tracer concentration at end of charging period and start or 500 ~ 0 ....c. u decay period. ...J 0 0 ;: I = infiltration, air changes per unit time, h (min). ;: 0 I = time of charging period, h (min). 0 ...J -500 LL The volume measured in this way can be compared to ...J -1000 LL geometric measurements. Differences indicate incomplete a: -1000 mixing or duct leakage. If the furnace blower is being used to < -2000 distribute and sample the tracer, loss of tracer due to duct -1500 leakage will cause the initial concentration c0 to be lower and -3000 the house volume will appear to be too large. Incomplete -2000 mixing also tends to cause the semi-log plot of tracer decay, -4000 Fig. 13, to depart from a straight line. -90 -60 -30 0 30 60 90 Item 4 refers to a situation that occurs if the physical PRESSURE, Pa volume of the test space is not the volume sampled by the tracer gas. The latter volume, called the effective volume, Fig. 18 Pressure vs. Flow Leakage from Pressurization can be larger or smaller than the physical volume of the Measurements. Solid Line Shows Leakage of House with space. A decay measurement, yielding an infiltration rate, I, Ductwork Open. Dashed Line Was Obtained When All is converted to an infiltration flow rate Q when I is multiplied Entrancesto Ductwork from Living Space Were Sealed by the effective volume. If the effective volume and physical with Plastic Sheets 10 volume are not equal, a significant error can exist in the calculated value of Q because the effective volume is measurements. Fig. 17 shows measurement results from a 48 unknown and must be approximated by the physical continuous-flow system. volume. The constant flow technique, which uses Eq 28 to The infiltration calculated using Eq 28 is shown on the right calculate Q, minimizes this problem. Whenever the system vertical axis. Tracer gas was injected at a rate of 13.6 L/h is near equilibrium (i.e., the concentration is nearly con (0.008 cfm) for the first 30 minutes of the measurement; the stant) the volume term enters the computation of the in flow was then reduced to a constant value of 5 L/h (0.003 filtration flow rate only as a small correction term. Conse cfm). The solid vertical lines at 50 and 150 minutes represent quently uncertainties in the effective volume cause only the contribution of the first term in Eq 28 to the value of Q; minor uncertainties in the value of the infiltration flow rate. the dashed vertical lines are the contributions of the correction term which includes the rate of change of con Fan Pressurization centration. Other tracer gas systems have been introduced using The fan pressurization method characterizes the building microprocessors for control, data logging, and calculation. 49 leakage rate independent of weather conditions. Equipment required for a quantitative measurement includes a blower, Mixing Problems a flow meter, a pressure gage, and possibly a smoke source Mixing problems present a major source of error. The or an infrared scanning device to locate leaks. ' 2 The blower tracer gas must be uniformly mixed throughout the test space is temporarily sealed to the building envelope and its flow so that the concentration of tracer gas measured accurately adjusted to produce a pressure drop of the order of 10 Pa represents the concentration in the space. For precision in (0.04 in . H 2 0) across the building shell. This is repeated at filtration measurements consult Ref 50. intervals of approximately 10 Pa (0.04 in. H 2 0) until the To assure adequate mixing: pressure-flow characteristic for the range from 0 to 50 Pa (0 0) I. Inject tracer gas at several points simultaneously using multiple to 0.2 in. H 2 is measured. The flow direction is reversed or perforated injection lines. to depressurize the building and the process is repeated. 2. Use auxiliary fans to initially mix the tracer gas throughout the Typical data obtained from these measurements are shown test space. Frequently the blower in a forced air heating or cooling in Fig. 18. system is used to distribute and sample the tracer. Several research· The data from these measurements can be used for a 17 ers, • ' 1 however, have reported addit ional infiltration whenever the comparison between structures by dividing the average blower is in operation. This was due to duct leakage (particularly flow (pressuriza tion and depressuriza tion) at SO Pa (0.20 in. when ducts pass through unconditioned spaces) and to a change in the H20) by the volume of the structure to give the number of effective volume sampled by the tracer gas (see item 4, below). air changes per hour at 50 Pa (0.20 in . H 0), as a defined 3. Analyze samples of air from several locations of the test space to 2 ensure that the concentration of tracer gas is uniform throughout. measure for comparing building tightness. Doors to closets, cupboards, etc. should be kept open to assure good A more useful number calculated from fan pre.ss urization mixing. If the concentrations cannot be made uniform, multichamber measurements is the effecti ve lea kage area. It can be u ed analysis must be used to adequately treat the data. for compa.rison and as a basis for modeling infiltration. If 4. Change the measurement technique, if necessary, to minimize the flow is assumed proportional to the square root (or to the mixing problem. the 0.65 power) of ·the pressure difference over the shell • Ventilation and Infiltration 11.19 (kinetic energy loss mechanisms are dominant) then a rates caused by wind and stack action for tall buildings (ASHRAE measurement of flow through the building shell can be used TRANSACTIONS, Vol. 83, Pt 2, 1977, p. 145). 17J . E. Janssen, J. J. Glatzel, R.H. Torborg, and U. Bonne; In to calculate the effective orifice area which would show the filtration in residential structures (Heat Transfer in Energy Con same pressure-flow characteristic. servation, ASME Symposium 8111/etfn, December 1977, p. 33). Fan pressurization-depressurization measures a property of 18W. C. Randall and E. W. Conover: Predetermining airatfon of a structure that varies little with time and is independent of industrial buildings (ASH VE TRANSACTIONS, Vol. 37, 1931. p. 605). 19Supplcment No. J to SBN 197S (Swedish Building Code, 197S). weather. It is a useful measurement for comparing the 20G. Born, and 0 . T. Harrje: Review and interpretation of air tightness of buildings. There is, however, no direct means for infiltration in residential h<' using (Internal Report, Center for En converting leakage rate to infiltration rate. If the leaks are of vironmental Studies, Princeton University). relatively the same size and uniformly distributed over the 210. R. Bahnfleth, T. D. Moseley, and W. S. Harris: ASHAE Research Report No. 1614-Measurement of infiltration in two structure, the infiltration rate will be about one-half the residen.ces; Part I-Technique and measured infiltration (ASHAE leakage rate for a pressure difference equal to the infiltration TRANSACTIONS, Vol. 63, 1957, p. 439). pressure difference. Further discussion rs presented in the 220. R. Bahnfleth, T. D. Moseley, and W. S. Harris: ASHAE discussion of infiltration models. Research Report No. 1615-Measurement of infiltration in two residences; Part 11- Compari on of variables affec ting infiltration Leakage Sites {ASHAE TRANSACTIONS, Vol. 63, 1957, p. 453). 2JR. C. Jordan, G. A. Erickson, and R. R. Leonard: Infiltration Leakage sites can easily be located during pressurization measurements in two research house (ASHRAE TRANSACTIONS, Vol. depressurization tests. Potential leakage sites can be tested 69, 1963, p. 344). qualitatively with smoke sources; when a building is 2'1C. W. Coblentz and P. R. Achenbach: Field measurements of air infiltration in ten electrically-heated houses (ASHRAE TRANS depressurized in cold weather, leakage sites can be felt with ACT.IONS, Vol. 60, 1963 , p. 358). the hand or face. Infrared thermography is also effective 25R. R. Laschober and J. H . Healy: Statistical analyses of air when a building is pressurized if there is sufficient indoor leakage in split-level residences (ASHRAE TRANSACTIONS, Vol. 70, outdoor temperature difference. 1964, p. 364). 26J. E. Janssen, T . J. Hill, and A. N. Pearman: Calculating in Acoustic sensors and the use of a simple window fan or filtration: an examination of handbook models (ASHRAE Paper No. whole house ventilation fan together with a smoke source OV -80-9-1, ASH RAE TRANSACTIONS, Pt 2, 1980). have both been employed to locate leaks in a building en 270. M. Sander and G. T. Tamura: A FORTRAN IV program to velope. 53 The techniques are not quantitative but are easily simulate air movement in multistory buildings (Computer Program performed and inexpensive. The obvious places to look for No. 37, Division of Building Research, National Research Council, Canada); R. E. Barrett and D. W. Locklin: Computer analysis of leakage sites are described in the Air Leakage section of this stack effect in hi gh-rise buildings (ASHRAE TRANSACTIONS, Vol. 74, chapter. Pt 2, 1968, p. 155). 28Q. T. Tamura and C. Y. Shaw; Studies on exterior wall air tightness and air infiltration of tall buildings {ASHRAE TRANS REFERENCES ACTIONS, Vol. 82, Pt I, 1976). l9G. L. Larson, 0 . W. Nelson, and R. W. Kubasta: ASHVE I ASHRAE Standard for Natural and Mechanical Ventilation, Research Report No. 909- Air Infiltration through double-hung 62-73; ANSI B. 194.1-1977. wood windows (ASHVE TRANSACTIONS, Vol. 37, 1931 , p. 571)_ 2 ASHRAE 62-73R (Draft Revision, January 15, 1980). 3-0W. M. Richtmann and C. Braat7.: ASHVE Research Paper No. 3A. K. Klauss, R. H. Tull, L. M . Roots, and J. R. Pfafflin: History 817-Effcct of frame caulking and storm wind ws on infiltration or the changing concepts in ventilation requirements (ASHRAE JOUR around and through windows (ASHVE TRANSACTIONS, Vo. 34, 1928, NAL, Vol. 12, No. 6, June 1970, p. 51). p. 547). . 4C. P. Yaglou, E. C. Riley, and 0. I. Coggins: Ventilation ll J. L. Weidt, J. Wcidt, and S. Sclkowitz: Field air leakage of requirements (ASHVE TRANSACT!ONS, Vol. 42, 1936, p. 133). newly installed residential windows (Proceedings of the ASHRAE Sc. P. Yaglou and W. N. Witherldge: Ventilation requirements, Pt DOE Conference on the Thermal Performance ofBuilding Envelopes, 2 (ASHVE TRANSACTIONS, Vol. 43, 1937, p. 423). Orlando, FL, Dcce mb~r 1979, LBL Report No. 9937). 6L. A. McHattie: Graphic visualization of the relations of l2F. C. Houghten and M. Ingels: ASHVE Re carch Report No. metabolic ruels: heal: 0 2: C01_: H20: Urine N. (Journal of Applied 786- lnflllration through plasttrcd and unplastercd brick walls Phy iology, Vol. 15, No. 4, 1960, p. 677). (ASHVE TRANSACTIONS, Vol. 33, 1927, p. 377). 7 J. V. Berk, C . D. Hollowell, and C . Lin: Indoor air quality JJG. L. Larson, D. W. Nelson, and C. Braatz: ASHVE Research measurements in energy-efficient houses (LBL-8894, EEB-Vent 79-4, Report No. 826-Air Infiltration through various types of brick wall Lawrence Berkeley Laboratory, University of California, Berkeley, construction (ASH VE TRANSACTIONS , Vol. 35. 1929, p. I 83). CA, July 1979). 34G. L. Larson, D. W. Nelson, and C . Braatz: ASHVE Research BN. Jonassen: Removal of radon daughters from indoor air by Report No. 851 - Air Infiltration through various types of brick wall mechanical means (Natural Radiation in Our Environment, Nordic construction (ASH VE TRANSACTIONS, Vol. 36, 1930, p. 99). Society for Radiation Protection, Geilo, January 1980). HQ. L. Larson, 0 . W. Nelson, and C. Braat.e: ASl-IVE Research 9B. E. Lee, M. Hussain, and B. Soliman: Predicting natural Report No. 868- Air infillration through various types of wood ventilation forces upon low-rise buildings (ASHRAE JOURNAL, Vol. frame con ln1ction (ASl-IVE TRANSACTIONS , Vol. 36, 1930, p. 397) . 22, No. 2, 1980, p. 35). l6Q. T. Tamura: Measurement of air leakage characteristics or ioo. T . Grimsrud, M. H. Sherman, R. C. Diamond, P. E. Condon, house enclosures (ASl-IRAE TRANSACTIONS, Vol. 81, Pl I, 1975, p. and A.H. Rosenfeld: Infiltration-pressurization correlations: detailed 202?. measurements in a California house (ASHRAE TRANSACTIONS, Vol. J G. T. Tamura and C. Y. Shaw: Air leakage data for lhc de ign of 85, Pt I, 1979). elevator and air shaft pressurization systems (ASH RAE TRANS 11 G . T. Tamura and A. G. Wilson: Pressure differences caused by ACTIONS, Vol. 82, Pt 2, 1976). wind on two tall buildings (ASHRAE TRANSACTIONS, Vol. 74, Pt 2, l8L. F. Schutrum, N. Ozisik, C. M. Humphrey, and J . T. Baker: 1968, p. 170). Air infiltration through revolving doors (ASHRAE TRANSACTIONS, 12T. C. Min: Winter infiltration through S\ inging-door entrances Vol. 67, 1961 , p . 488) . in multistory buildings (ASHAE TRANSACTIONS. Vol. 64, 1958, p. l9T. C. Min: Engineering concept and design of controlling in 421). filtration and trarfic through entrances in tall commercial buildings llG. T . Tamura and A. G. Wilson: Pressure differences for a ninc (111rernarional Conference on Heating, ve,,rilating and Air Con story building as a result of chimney effect and ventilation system ditioning, London, September 27- 0ctober 4, 1961 ). operation (ASl-IRAE TRANSACTIO ·s, Vol. 72, Pt 1, 1966, p. 180). 40W. Rudoy; Cooling and heating load calculation manual (GRP 14 0. T. Tamura and A. G. Wilson:Pn: sure diffrrcnce caused by 158, ASHRAE, 1979). chimney effect in three high buildings (ASH RAE TRANS CTtONS, Vol. 4 1M. H. Sherman and D. T. Grimsrud: In filtration-pres urization 73, Pt 2, 1967, p. II.I.I). correlation: simplified phy ical modeling (ASH RAE TRAl'ISAC!lONS , 1sc. T. Tamura and A. G. Wll $o n: Air leakage and pressure Vol. 86, Pl 2, 1980, LB Report o. 10 163) . measurements on two occupied houses (ASHRAE TRANSACTIONS, 42M . H. hcrman, D. T. Grimsrnd, and R. C. Sond.:r.:ggcr: The Vol. 70, 1964, p. 110). low pressure leakage function of building (Proceedings of the 16C. Y. Shaw and G. T. Tamura: The calculatio n of air infiltration ASHRAE -DOE Conference 011 the Thermal Performance of Building 22.20 CHAPTER22 1981 Fundamentals Handbook Envelopes, Orlando, FL, December 1979, LBL Report No. 9162). 52A. K. Blomsterberg and D. T. Harrje: Approaches to evaluation 43 R. K. Beach: Relative tightness of new housing in the Ottawa area of air Infiltration energy losses in buildings (ASHRAE TRANSACTIONS, (Building ResearcJ1 Note No. 149, Nalional Research Council of Vol. 85, Pt I, 1979, p. 797). Canada, June 1979). no. N. Keast: Acoustic location of infiltration openings in 4-1 Reeommendations for calculation of wind effects on buildings buildings (Bolt, Beranek and Newman Report No. 3942, October and structures (European Convention for Co11structio11al Steelwork, 1978). Brussels, September 1978). 45Q. T. Tamura: The calculation of :1ouse infiltration rates BIBILIOGRAPHY (ASHRAETRANSACTIONS, Vol. 85, Pt I, 197~). 46W. F. deGids: Calculation method 'or the natural ventilation of J. B. Dick: Measurement of ventilation using tracer gas technique buildings (Publication No. 633 TNO Research lnstitule, DELFT, (ASHVE Journal Section, Heating, Piping and Air Conditioning, 1978); O. K. Alexander and D. W. Etheridge: The British gas multi May 1950, p. 131). cell model for calculating ventjlation (ASHRAE TRANSACTIONS, Vol. J. B. Dick and D. A. Thomas: Ventilation research in occupied 86, Pt2, 1980). houses (Journal of the lllstitution of Heating and Ventilating 47 D. T. Grimsrud, M. H . Sherman, J _E. Janssen, A. 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Green: Combined thermal and air leakage (Proceedings of the /st TEA Symposium of the Air Infiltration Centre, performance of double windows (ASH RAE TRANSACTIONS, Pt 2, Vol. London, 1980, LBL Report No. 10705). 76, 1970). 51M. B. Steward, T. R. Jacob, and J. G . Winston: Analysis of Standard for the /11sta//ation of Air Conditio11i11g a11d Ventilating infiltration by tracer gas technique, pressurization tests and infrared Systems, No. 90A, and Standard for the lnstallatlon of Warm Air scans (Proceedings of the ASHRAE-DOE Conference on the Thermal Heating and Air Conditioning Systems, No. 908 (National Fire Per/ormance of Building Envelopes, Orlando, FL, December 1979) . Protection Association, latest revisions) . '