Document evwQG3M24ZD6dk1nNNeZjVLng

HEATING VENTILATING AIR CONDITIONING GUIDE 1941 Table 2. Infiltration Through Windows Expressed in Cubic Fed per Foci of Crack per Hour* Tm or Window R PM* WITH Wind Velocity, Miles per Houb 5 10 15 20 25 30 Around frame in masonry wall--not calkedb 3.3 8.2 14.0 20.2 27.2 34.6 Around frame in masonry wall--calked^___ 0.5 1.5 2.6 3.8 4.8 5.8 Around frame in wood frame construction!*-- 2.2 6.2 10.8 Double-Hung Wood Sash Total for average window, non-weatherstripped, 36-in. crack and 36-im clearances Windows Includes wood frame leakA^ed . , 6.6 21.4 39.3 (Unlocked) Ditto, weatheratrippedd 4.3 13.0 23.6 16.6 59.3 35.5 23.0 30.3 80.0 103.7 48.6 63.4 Total for poorly fitted window, non-weather- stripped, 36-tn. crack and 36-in. clearances Includes wood frame lealraged 26.9 69.0 110.5 153.9 199.2 249.4 Ditto, weatherstrippedd 5.9 18.9 34.1 51.4 70.5 91.5 Double-Hung Non-weatherstripped, locked-__ Metal Non-weatherstripped unlocked Windows! Wffttheratrinneri unlocked 20 45 70 96 125 154 20 47 74 104 137 170 6 19 32 46 60 ,76 Industrial nivnterl. Wi-in crockk 52 108 176 244 304 372 Rolled Architectural projected, 36*>n. crackb_____ 15 36 62 86 112 139 Section Architectural projected, 36-in. crackh_____ 20 52 88 116 152 182 Steel Residential casement. Wi-in. crack! 6 18 33 47 60 74 Sash Windows'1 Residential easement, 36-in. crack!__ ._____ Heavy casement section, projected, 16-in. cracki 14 3 32 10 52 18 76 100 128 26 36 48 Heavy casement section, projected 36-in. cracki- 8 24 38 54 72 92 Hollow Metal, vertically pivoted window*.____ 30 88 145 186 221 242 The values given in this table, with the exception of those for double-hung and hollow metal windows, are 20 per cent less than test values to allow for building up of pressure in rooms, and are based on test data reported in the papers listed at the end of this chapter. . ^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 prevented by calking. For the additional reason that calking is not done perfectly and deteriorates with rime, it is considered advisable to choose the masonry frame leakage values for calked frames as the average determined by the calked and not-calked tests. cThe fit of the average double-hung wood window was determined as >-in. crack and 36-in. clearance by measurements on approximately 600 windows under heating season conditions. <*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 per cent efficiency of frame calking. . A 36"in. crack and clearance represents a poorly fitted window; much poorer than average. ^Windows tested in place in building. eindustria] pivoted window generally used in industrial buildings. Ventilators horizontally pivoted at center or slightly above, lower part swinging out. ^Architectural projected made of same sections as industrial pivoted except that outside framing member 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 arras. J6-in. crack i3 obtainable in the best practice of manufacture and installation, 26-in. crack considered to represent average practice. *Of same design and section shapes as so-called heavy section casement but of lighter weight. in. crack is obtainable in the best practice of manufacture and installation. 36-in. crack considered to represent average practice. iMade of heavy sections. Ventilators swing in or out and stay set at any degree of opening. J6-in. crack is obtainable in the best practice of manufacture and installation, krin. crack considered to represent average practice. kWitb reasonable care in installation, leakage at contacts where windows are attached to steel frame work and at mullions is negligible. With 36*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. 104 CHAPTER 4. AIR LEAKAGE WINDOW LEAKAGE The amount of infiltration for various types of windows is given in T ble 2. The fit of double-hung wood windows is determined by crack d clearance. Crack thickness is equivalent to one-half the difference hptween the inside window frame dimension and the outside sash width. TTie difference between the width of the window frame guide and the cash thickness is considered as the clearance. The length of the perimeter oening 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 oerimeter length plus the meeting rail length. Values of leakage shown in Table 2 for the average double-hung wood window were, determined by setting the average measured crack and clearance found in a field survey of a large number of windows on nine windows tested in the laboratory. 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, lust 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 doublehung 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. Locking, 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 feet of sash section in contact with steel work at mullions should be figured at 25 per cent of the values for industrial pivoted windows as given in Table 2. When storm sash are applied to well fitted windows, very little re duction in infiltration is secured, but the application of the sash does give an air space which reduces the heat transmission and helps prevent the frosting of the windows. When storm sash are applied to poorly fitted windows, a reduction in leakage of 50 per cent may be secured. 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 doublehung wood window may be used. If poorly fitted, twice this figure should 105