Document 15L4pXEjaRjpqNjr0wm3oXNva

of and 1937American Society Heating Ventilating Engineers Guide, Table 2. Infiltration Through Windows Expressed in Cubic Feet Per Foot of Crack per Hour* Ttpr op Window Remarks Wind Velocity,' Miles per Hour 5 10 15 20 * 25 30 Around frame in masonry wall--not caikedb 3.3 8.2 14.0 20.2 27.2 34.6 Around frame in masonry wall--calkedb__ 0.5 1.5 2.6 3.8 4.8 5.8 Around frame in wood frame constructionb__ 2.2 6.2 10.8 Double-Hung Total for average window, non-weather- Wood Sash Windows stripped, 56-in. crack and $6-in. clearance^ Includes wood frame leakage^ 6.6 21.4 39.3 (Unlocked) Ditto, weatherstrippedd 4.3 15.5 23.6 16.6 59.3 35i5 23.0 30.3 80.0 103.7 48.6 63.4 Total for poorly fitted window, non-weather- stripped, 5-in. crack and 56-in. clearance. Includes wood frame leakaged_ ____ 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 20 45 70 96 125 154 Metal Non-weatherstripped, unlocked.......... ........... 20 47 74 104 137 170 Windowsf Weatherstripped. unlocked_________ 6 19 32 46 60 76 Rolled Section Steel Sash Windows1* Industrial pivoteds. 56-in- crar.k............. 52 108 Architectural projected, 56-in- crackh______ 15 36 Architectural projected, 56-in. crackh ____ 20 52 Residential casement, 56-in. crack>. 6 18 Residential casement, 56-in. crack* 14 32 Heavy casement section, projected, 56-in- 3 10 Heavy casement section, projected 56-in. 8 24 176 62 88 33 52 18 38 244 86 116 47 76 26 54 304 372 112 139 152 182 60 74 ioo 128 36 ' 48 72 92 Hollow Metal, vertically pivoted window*._____ 30 88 145 186 221 242 aThe 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 56-in. clearance by . measurements on approximately 600 windows under heating season conditions. dThe 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 y jbut apply as well to masonry construction assuming a 50 per cent efficiency of frame calking. * eA $6-in. crack and clearance represents a poorly fitted window, much poorer than average. fWindows tested in place in building. slndustrial pivoted , window generally used in industrial buildings. Ventilators horizontally pivoted at center or slightly above, lower part swinging out. bArchitectural 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. 56-in- crack is obtainable in the best practice of manufacture and installation, J6-in. crack considered to represent average practice. Of same design and section shapes as so-called heavy section casement but of lighter weight. 56-in- crack is obtainable in the best practice of manufacture and installation, 56-in- crack considered to representaverage practice. JMade 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, 56-in. crack considered to represent average practice. kWith reasonable care in installation, leakage at contacts where windows are attached to steel frame work and at mullions is negligible. With 56-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 twindows in the table. . 136 Chapter 6--Air Leakage ash are applied to well fitted windows, very little reduction in infiltration ? secured, but the application of the sash does give an air space which "educes 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 be used. If weatherstripped, the values may be reduced one-half.' A single door which is frequently opened, such as might be found 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 thp coldest and windiest weather. In the case of infiltration through swinging and revolving doors engi neers are not in full agreement at the present time regarding the allowances for cooling load determinations. Some references to recently published data are given at the end of this chapter. SELECTION OF WIND VELOCITY 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 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 are given in Table 2, Chapter 7. In considering 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 necessi tate 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 worst combination of outside temperature and wind velocity for a given building and locality. The usual procedure, as already explained, is to select an outside temperature basigd on the lowest on record and the average wind velocity during the months of December, January and February. The direction of prevailing winds may usually be included within an 137