Document pmD0rdYyvRVZR0raLZ9N0b8QX

220 CHAPTER 11 Table 2. Infiltration Through Windows Expressed in Cubic Fee', per Foot of Crack per Hour' 1953 Guide' Type of Window Remarks Wind Velocity, Milesper Hotra 5 ; 10 15 20 25 30 Around frame in masonry wall--not calkedb Around frame in masonry wall--calkedb Around frame in wood frame construction1* Double-Hung Wood Sash Windows (Un- lotal for average window, non-weatheristripped,' Ma-m. crack and %4-m. clearance. Includes wood frame leakage*1 Ditto, weatherstripped11 a2rly fitte? wl?d?w' non-weather^Includes w*o**o-d!"fracmre *leaaknaidmd5^,-in. clearance." Ditto, weatherstripped*1. . Double-Hung Metal Windows1 Non-weatherstripped. locked Non-weatherstnpped, unlocked...................... `` ' Weatherstripped, unlocked.................. 3 2 27 6 20 20 6 8 6 2 19 45 47 19 Industrial pivoted. He-in. crack* . Rolled Section Steel Sash Windowek Architectural projected. Ha-in. crack1* Architectural projected, H4-in. crack1*......... 52 15 36 20 - -52 Residential casement, Ma-in. crack* Heavy casement section, projected, M4-in. crack! Heavy casement section, projected, Ma-in. crack* 14 3 8 32 10 24 14 20 27 35 ; 11 17 5 23 6' 30 59 80 104 36 49 63 i 34 199 249 51 71 92 70 96 125 154 74 32 104 46 137 60 170 304 372 88 116 112 152 139 182 47 60 74 100 128 18 38 26 36 54 `72 48 92 Hollow Metal, vertically pivoted window' 30 88 145 188 221 242 * The values given in this table, with the exception of those for double-hung and hollow metal windows are 20 percent less than test values to allow for building up of pressure in rooms, and are based on test data, eported in the papers listed in chapter footnotes. ` b The values given for frame leakage are per foot of sash perimeter, as determined for double-hung wood windows. Some of the frame leakage in masonry walls originates in the brick wall itself, and cannot be pre vented by calking. For the additional reason that calking is not done perfectly and deteriorates with time, it is considered advisable to choose the masonry frame leakage values for calked frames as the average deter mined by the calked and non-calked tests. c The fit of the average double-hung wood window was determined as Mo-in. crack and %4-in. clearance by measurements on approximately 600 windows under heating season conditions. d The values given are the totals for the window opening per foot of sash perimeter, and include frame leakage and so-called elsewhere leakage. The frame leakage values included are for wood frame construction, but apply as well to masonry construction assuming a 50 percent efficiency of frame calking. A aViu, crack and clearance represent a poorly fitted window, much poorer than average. f Windows tested in place in building, so that no reduction from test values is necessary, as mentioned in footnote a. 8 Industrial pivoted window generally used in industrial buildings. Ventilators horizontally pivoted at center or slightly above, lower part swinging out. h Architecturallyprojectedmade of same sections as industrial pivoted, except that outside framing mem ber is heavier, and it has refinements in weathering and hardware. Used in semi-monumental buildings such as schools. Ventilators swing in or out and are balanced on side arms. Ms-in. crack isobtainableinthe best practice of manufacture and installation, H^-in. crack considered to represent average practice. * Of same design and section shapes as so-called heavy section casement, but of lighterweight. %4-in. crack pisraocbttiacein.able in the best practice of manufacture and installation, H2-in. crack considered torepresentaverage * Made of heavy sections. Ventilators swing in or out and stay set at any degree of opening. Ha-ih, crack pisroabcttiacien.able in the best practice of manufacture and installation, Ms-in. crack considered torepresentaverage k With reasonable care in installation, leakage at contacts where windows are attached to steel frame work and at mulliona, is negligible. With %4-in. crack, representing poor installation, leakage at contact with steel framework is about one third, and at mullions, about one-sixth of that given for industrial pivoted windows in the table. The amount of infiltration for various types of windows is given in Table 2.2 The fit of double-hung wood windows is determined by crack and clearance. Crack thickness is equivalent to one-half the difference be tween the inside window frame dimension and the outside sash width. The difference between the width of the window frame guide and the sash thickness is considered as the clearance. The length of the perimeter opening or crack for a double-hung window is equal to three times the width, plus two times the height, or in other words, it is the outer sash perimeter length, plus the mating rail length. All of the window crack in any given infiltration and Ventilation 221 room is not necessarily used in.estimating the infiltration heat loss by the crack method. The length of crack to be selected in any given case de pends on the number of exposed sides, as explained in Chapter 12. Values of leakage shown in Table 2 for the. average double-hung wood window were determined by using, on nine windows tested in the labora tory, the average measured crack and clearance of a large number of windows found in a field survey. In addition, the table gives figures for a poorly fitted window. All of the figures for double-hung wood windows are for the unlocked condition. Just how a window is closed, or fits when it is closed, has considerable influence on the leakage. The leakage will be high if the sash are short, if the meeting rail members are warped, or if the frame and sash are not fitted squarely to each other. It is possible to have a window with approximately the average crack and clearance that will have a leakage at least double that of the figures shown. Values for the average double-hung wood window in Table 2 are considered to be easily obtainable figures, provided the workmanship on the window is good. Should it be known that the windows under consideration are poorly fitted, the larger leakage values should be used. Locking a window generally decreases its leakage, but in some cases may push the meeting rail members apart and increase the leakage. On windows with large clearances, locking will usually reduce the leakage. Wood casement windows may be assumed to have the same unit leakage as for the average double-hung wood window when properly fitted. Lock ing, a normal operation in the closing of this type of window, maintains the crack at a low value. For metal pivoted sash, the length of crack is the total perimeter of the movable or ventilating sections. Frame leakage on steel windows may be neglected when they are properly grouted with cement mortar into brick work or concrete. When they are not properly sealed, the- linear feqt of sash section in contact with steel work at mullions should be figured at 25 percent of the values given in Table 2 for industrial pivoted windows. When storm sash are applied to well fitted windows, some reduction in infiltration is secured; the application of the sash provides an air space which reduces the heat transmission and helps prevent the frosting of the win: dows.3 By applying storm sash to poorly fitted windows, a reduction, in leakage of 50 percent may be obtained, the effect, so far as air leakage is concerned, being roughly equivalent to that obtained by the installation of weatherstrips. Door Leakage Doors vary greatly in fit because of their large size and tendency to warp. For a well fitted door, the leakage values for a poorly fitted double-hung wood window may be used. If poorly fitted, twice this figure should be used. If weatherstripped, the values may be reduced one-half. A single door which is frequently opened, as might be the case in a store, should have a value applied which is three times that for a well fitted door. This extra allowance is for opening and closing losses, and is kept from being greater by the fact that doors are not used as much in the coldest and windi est weather. The infiltration rate through swinging and revolving doors is generally a matter of judgment by the engineer making cooling load determinations, and in the absence of adequate research data, the values given in Table 3 represent current engineering practice. Some tests of infiltration through swinging and revolving doors have been reported.4 The data in Table 3