Document M4YvJNv240OpDMGqXQxreZpr9

American Society of Heating and Ventilating Engineers Guide, 1934 Table 2. Infiltration Through Windows Expressed in Cubic Feel per Foot of Crack per Hour* Ttpb or Window Reiubks Wikd Veloott, Miles pee Houb 10 15 Around frame in masonry wall-- not calkedb.............. ..... 3.3 8.2 14.0 20.2 27.2 34.6 Around frame in masonry wall-- calked1*..................... 0.5 1.5 2.6 3.8 4.8 5.8 Around frame in wood frame construction15........... 2.2 6.2 10.8 Double-Hung (Total for average window, nonWood Sash weatherstripped, Ke-in. crack Windows and %4-in. clearance6. In (Unlocked) cludes wood frame leakage*1__ 6.6 21.4! 39.3 16.6 59.3 23.0 30.3 80.0 103.7 Ditto, weatherstripped*1.............. 4.3 15.5 23.6 35.5 48.6 63.4 (Total for poorly fitted window, I non-weatherstripped, %2-in. crack and clearance6. Includes wood frame leakage"1. 26.9 69.0 110.5 153.9 199.2 249.4 (Ditto, weatherstripped*1.. 5.9 18.9 34.1 51.4 70.5 91.5 Double-Hung Non-weatherstripped, locked___ 20 Metal Non-weatherstripped, unlocked- 20 Windows1 Weatherstripped, unlocked_____ 6 45 47 19 70 74 32 96 104 46 125 154 137 170 60 76 Rolled Industrial pivoted, Ha-in. crack 52 (Architectural projected,11 %4-in. 108 176 244 304 372 Section Steel Sash Windows'6 crack..--................. -.......... .... Residential casement,1 M2*ip- crack. Heavy casement section, pro 20 14 52 32 88 52 116 152 208 76 100 128 jected,) H2-in- crack 8 24 38 54 72 96. Hollow Metal, vertically pivoted window1--__ 30 88 145 186 221 242 The values given in this table 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. bThe 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 time, 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 26-in. clearance Jby measurements on approximately 600 windows under heating season conditions. dTbe 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. ^Industrial 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 refinements in weathering and hardware. Used in semi-monumental buildings such as schools. Ventilators swing in or out and are balanced on side arms. iOf same design and section shapes as so-called heavy section easement but of lighter weight. jMade of heavy sections. Ventilators awing in or out and stay set at any degree of opening. kWith reasonable care in installation, leakage at contacts where windows are attached to steel frame work and at mullions is negligible. With 26-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. 96 Chapter 6--Air Filtration sash leakage, the length of crack in double-hung windows is equal to the perimeter of sash plus length of meeting rail. For steel sash the length of crack is the aggregate perimeter of the movable of ventilating sections plus the linear feet of sash section in contact with steel work (at a different leakage rate) at mullions. The crack length for frame windows (when frame is not calked) is the perimeter of the frame. Steel sash frame properly grouted with cement mortar into brickwork or concrete is not to be counted as crack. The value of storm sash is shown by the curves of Figs. 4 and 5. A study of the curves leads to the conclusion that a storm sash is of little value in reducing infiltration when applied to a well fitted window, but that a reduction of 50 per cent might be expected when storm sash is applied to a poorly fitted or loose window. Infiltration through door cracks may be assumed to be twice that of window cracks. WIND VELOCITY TO BE CHOSEN Although all authorities do not agree upon the value of the wind veloc ity that should be chosen for any given locality, it is common engineering Fig. 3. Diagram Illustrating Crack and Clearance practice to use the average wind velocity during the three coldest months of the year. Until this point is definitely established the practice of using average values will be followed. Average wind velocities for the ^months of December, January and February for various cities in the United States and Canada <gre given in Table 2, Chapter 7. In nonsidering both the transmission and infiltration losses, the more exact procedure would be to select the outside temperature and the wind velocity corresponding thereto, based on Weather Bureau records, which would result in the maximum heat demand. Since the proportion of transmission and infiltration losses varies with the construction and is different for every building, the proper combination of temperature and wind velocity to be selected would be different for every type of building, even in the same locality. Furthermore, such a procedure would neces sitate a laborious cut-and-try process in every case in order to determine the worst combination of conditions for the building under consideration. It would also be necessary to consider heat lag due to heat capacity in the /case of heavy masonry walls, and other factors, to arrive at the most accurate solution of the problem. Although heat capacity should be con sidered wherever possible, it is seldom possible to accurately determine the 97