Document reK2Y221JvZ44wO32Y5XL1o2a

HEATINC VENTILATING AlR CONDITIONING GUIDE 1943 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. 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 vajue applied which is three times that for a well fitted Table 3. Infiltration Through Outside Doors for Cooling Loads2 Expressed in Cubic Feet per Minute per Person Entering Room Application Bank....................................... . Barber Shop Broker's Office r- Candv and Soda............ Department Store Dress Shob.... ................... ..... .. Drug Store............. Furrier____ ____ Hospital Room........................... Lunch Room Men's Shop....................................................... Office'Buildine...:............................ Public Building....... .... Restaurant................................................... Shoe Store..... - Pair 36 in. Swinging DoEoNrTsR,ASNiCnggble 75 45' 70 60 80 25 70 25 35 50 35 3 020' 25 . 2 5' 3.5 For doors located in only one wall or where doors in other walls are of revolving type. bVestibules with double coir 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. 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 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; 'Fuel Saving Resulting from the Use of Storm Windows and Doors, by A. P. Kratz and S. Konro (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 Characteristtcs of Entrance Doors, by A. M. Simpson (Refrigerating Engineering, June, 1936).' 124 CHAPTER 5. AIR LEAKACE 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 ofchanges 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. 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. 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 Table 4. Air Changes Taking Place under Average Conditions Exclusive of Air Provided for Ventilation Kind op Room os Building Numbsb op Aib Cbamgbs Taking Place per Hocb -i va 2 2 }4 to % 2 to 3 ' ' . .2 > 1 to 2 1 to 2 2 2 to 3 1 14 to 3 to leave at higher levels6. Although it is not appreciable in low buildings, this loss should be considered in tall, single story buildings with openings near the ground level and near the ceiling. - Also in tall, multi-story buildings it may be a considerable item unless the sealing between various floors arid 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 from it at higher levels. Oh the other hand; the wind velocity at lower, levels may be somewhat abated by surrounding obstructions. Further more, the chimney effect is reduced in multi-story buildings by the partial isolation of floors, thereby preventing free upward movement, so that wind and temperature difference, may seldom, cooperate to the fullest extent.. Making the rough assumption that th,e neutral zon& is located at A.S.H.V.E. Research Reports No. 994--Wind Velocities'Near a Building and Their Effect on Heat Loss by F. C. Houghten, J. L. Blackshaw and Carl Gutberiet (A.S.H.V.E. Transactions, Vol. 40. 1934. o. 387). No. 1069--Heating Requirements of an Office Building as Influenced by the Stack Effect, by F. C. Houghten and Carl Gutberiet (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 Buddings, by Axel Mann (A.S.H.V.E. Transactions,. Vol. 40, 1934, p. 377). Neutral Zone in Ventilating, by J. E. Emswiler (A.S.H.V.E. Transactions, Vo!. 32. 1926, p. 59). 125