Document vBmM8dz0B7K4rM0marwz5Qgm

American Society of Heating and Ventilating Engineers Guide, 1934 IZ ft u 1u A 09 ft a?, 07 & 06 u j1. c j 7 7 L 1 ' . i IT // J t '\ - 1 1 7 t 1 7 7h T t r 7 v /T 7f. A'WfTHotrr Storm Sash |a5 T A Q Q3 1 1 j /a , L r J L /fa 02 1 / a go/ ( fat A 1/ ^0 0 50 too With Folk Tuba/Buttons D- Sane As C With Wool 150 zoo 250 300 Infiltration CjF.HPem Foot OfCback 50.03 4569 t s 4069 ($ S 3540 X fc Z&90 9 ?f>4? 0 Fig. 4. Infiltration through Sash Perimeter of Window with and without Storm Sash--M4-IN. Crack and >62-1^- Clearance 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 based 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 angle of about 90 deg. The windows that are to be figured for prevailing I.Z BA/ k/.O ^ at 07 lae |Q5 ^04 03 L%Q2 *0 0 c [I f7 7 f fa r j1 7) r t t t r / fa 7 f/ l 1 tr- rl i t 7< T 1 L t t 7 ti / 7 / 7 A-Without 5tobm Sash B Stobm Sash Suspended C-Storm Sash Fastened s Wrm Foue Turn Buttons Dili J_L 1 1 III 11 1 r 50 /00 150 200 250 300 350 400 Infiltbaikn CF.H. Per Foot Of Cback 5003 4569 | 4069 | <0 35/1Q < 26.90 6 | 2042 0 Fig. 5. Infiltration through Sash Perimeter of Window with and without" Storm Sash--J^-in. Crack and y%-in. Clearance 98 Chapter 6--Air Filtration , on_Prevailing winds will ordinarily each occupy about one-half the an "meter of the structure, the proportion varying to a considerable extent wth the plan of the structure. (See discussion of wind movement in Chapter 4). CRACK USED FOR COMPUTATIONS In no case should the amount of crack used for computation be less. , half of the total crack in the outside walls of the room. Thus, in a' t`Tm w;th one exposed wall, take all the crack; with two exposed walls, !ke the wall having the most crack; and with three or four exposed walls, mke the wall having the most crack; but in no case take less than half the total crack. For a building having no partitions, whatever wind enters through the cracks on the windward side must leave through the cracks on the leeward side. Therefore, take one-half the total crack for com puting each side and end of the building. 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 3. Table 3- Air Changes Taking Place under Average Conditions Exclusive of Air Provided for Ventilation Kind or Room ob Building Numbbb or Ant Changss Taking Placb pur Houa Living Rooms.--...................................................................... 1 m 2 2 H to Va 2 to 3 2 1 to 2 1 to 2 2 2 to 3 1 M to 3 MULTI STORY BUILDINGS In tall buildings, infiltration may be considerably influenced by tem perature difference or chimney effect which will operate to produce a head that will add to the effect of the wind at lower" levels and subtract from it at higher levels. On 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 preventing free upward movement, so that wind and temperature difference may seldom cooperate to the fullest extent. Making the rough assumption that the neutral zone is located at mid height of a building, and that the temperature difference is 70 F, the 99 ;