Document 6RV7OdXzbrYKjQyLG2n4VYwpo

HEATING VENTILATING AIR CONDITIONING GUIDE 1944 Table 3. Infiltration Through Outside Doors for Cooling Loads3 Expressed in Cubic Feet per Minute per Person Entering Room Application Pair 36 in. Swinging Doors, Single Entrance** Department Store.............. Dress Shop Dnip Store 7.5 4.5 7.0 6.0 8.0 2.5 7.0 2.5 . Application Pair 36 in. Swinging Doors. Single Entrance b 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. bVestibules 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. 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 windows3. By applying storm sash to poorly fitted windows, a reduction 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 closingJosses 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 determinations and 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 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 assuming a 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 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, Healing, Piping and Air Conditioning, June, 1936, p. 345). Infiltration Character* istics of Entrance Doors, by A. M. Simpson (Refrigerating Engineering, June, 1936). 122 CHAPTER 5. AIR LEAKACE Ta rle 4 Air Changes Taking Place under Average Conditions Exclusive. . able QF Air provided for Ventilation3 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...... 1m 2 2 Kind of Room or Building Number of Air. Changes taking Place per Hour Rooms with no windows or outside doors.----------- O0 Bath Rooms........................ Stores-- ........................-- 2 2 1 to 3 For rooms with weatherstripped windows or storm sash, use H these values, where applicable. 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 ` air change method to factories and industrial and commercial buildings because of wide variations in the type and percentage of fenestration which is the principal source of air leakage in such buildings. INFILTRATION DUE TO TEMPERATURE DIFFERENCE The air exchange due to temperature difference, inside to outside, is a chimney effect, causing air to enter through openings at lower levels and to leave at higher, levels3. Although it is not appreciable in low buildings, this loss should be considered in tall, single story buildings with openings near the ground level send near the ceiling. Also in tall, multi-story buildings it may be a considerable item unless the sealing between various floors and rooms is quite perfect. In tall buildings, temperature difference or chimney effect will produce a head that will add ,to the effect of the wind at lower levels and subtract A.S.H.V.E. Research Reports No. 994--Wind Velocities Near a Budding and Their Effect on Heat Loss, by F. C. Houghten, J. L. Blackshaw and Carl Gutberlet (A.S.H.V.E. Transactions, Vol. 40, 1934, p. 387). No. 1069--Heating Requirements of an Office Building as Influenced by the-Stack Effect, by F.. C. Houghten and Carl Gutberlet (A.S.H.V.E. Transactions, Vol. 43, 1937, p. 437). Flue Action in High Buildings, by H. L. Alt (A.S.H.V.E. Journal Section, Heating. Piping and Air Conditioning, May, 1932, p. 376). Influence of Stack Effect on the Heat Loss in Tall Buildings, by Axel Marin (A.S.H.V.E. -- ------ -------------- ir-1 Af\ low 8771 , , 123