Document np2VE0k38bnQK03xbLv4nB3EG

114._______________________________Chapter 5 _____________^1945 Guide clearance of a large number of windows found in a field survey 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. 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 the1 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 windows8. By applying storm sash to poorly fitted windows, areduction in leakage of 50 per cent 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 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 the coldest and windiest weather. ' The infiltration rate through swinging and revolving doors is generally a matter of judgment by the engineer making cooling load determinationsand in the absence of adequate research data the values given in Table 3 represent current engineering practice4. These values are based on the average number of persons in a room at a specified time, which may also 'Fuel Saving Resulting from the Use of Storm Windows and Doors, by A. P. Kratz and S. Konzo (A.S.H.V.E. Transactions, Vol. 42, 1936. p. 87)., .'The Infiltration Problem of Multiple Entrances, by A. M. Simpson and K. B. Atkinson (A.S.H.V.E. Journal Section, Heating, Piping and Air Conditioning, June, 1936. p. 345). Infiltration Character' istics of Entrance Doom, by A. M. Simpson (Refrigerating Engineering, June, 1936). 44ir Leakage 115 Table 3. Infiltration Through Outside Doors for Cooling Loads4 Repressed in Cubic Feet per Minute per Person Entering Room Application Pair 36 in. Swinging Doors, Single' Entrance* Application . Pair 36 in. Swinging Doors, Single Entrance* Bank............1....... ................. Candy and Soda...... ............ Department Store............... Drug Store............................ 7.5 4.5 7.0 6.0 . 8.0 2.5 7.0 2.5 Hospital Room_____:.......... Office....... ' Office Building______ _____ Restaurant___ ___ ________ 3.5 5.0 3.5 3.0 2.0 2.5 2.5 3.5 For doors located in only one wall or where doors in other walls are of revolving type. ; ^Vestibules with double pair swinging doors, infiltration may be assumed 75 per cent of swinging door values. Infiltration for 72 in. revolving doors may be assumed 60 per cent of swinging door values. be the same occupancy assumed for determining the outside ventilation requirements outlined in Chapters 2 and 7. Air Change Method The amount of air leakage is sometimes roughly estimated by assuminga certain number of air changes per hour for each room, the number of changes assumed being dependent upon the type, use and location of the room, as indicated in Table 4. This method may be used to advantage as a check on the calculations made in the more exact manner. On the other hand, where it is not possible to determine or pre-determine with accuracy the width of crack or clearance of windows, or where other sources of air leakage cannot readily be evaluated, as is often the case, the use of the air change method may be justified. The values in Table 4 may be used with reasonable accuracy for resi dences and are the requirements for each room. The total infiltration allowance for the entire building should be one-half the sum of the infiltration allowances of the individual rooms, since whatever air enters on the windward side generally leaves the building on the leeward side and the infiltration requirements therefore do not exist simultaneously on all sides or in all rooms. An allowance of one air change per hour for all sources of air leakage for the entire volume may be considered average for a well constructed residence. The air leakage for vestibules due to opening and closing of doors is sometimes based on the air change method, even though the air leakage estimates for other rooms are based on the crack method. Except for vestibules and reception halls, it is not advisable to attempt to apply the Tafle 4. Air Changes Taking Place under Average Conditions Exclusive of Air Provided for Ventilation* Kind of Room or Building Number op Air Changes taking Place per Hour Kind of Room or Building Number of Air Changes taking Place per Hour Rooms, 1 side exposed Rooms, 2 sides exposed... Rooms, 3 sides exposed Rooms, 4 sides exposed i Rooms with no windows m or outside doors........ ....... ViioH 2 2 to 3 2 Reception Halls................... 2. Bath Rooms................ ......... 2 Stores...... ............................... 1 to 3 "For rooms with weatherstripped windows or storm sash, use Vi these values, where applicable.