Document DGbpyORq7Jwyx1yKjxjd6Lo0d

American Society 0/ Heating and Ventilating Engineers Guide, 1930 The most convenient values for use in infiltration calculations are the coefficients of infiltration for the particular kind of crack with a wind velocity of 15 miles per hour under average conditions, with J^6 in. crack and 14i in. clearance reduced by 20 per cent (Table 39, Part II). For a wind velocity other than 15 miles per hour, use the proper velocity for that locality in place of 15. For temperature gradients other than 70 deg. multiply the value given in the tables by the new temperature gradient and divide by 70. For special cases involving unplastered walls or storm sash use values obtained from Table 37 or Figs. 7 and 8. Infiltration Due to Temperature Difference Even without wind movement, a difference of temperature between inside and outside of a building will cause the pressure state inside to be <0 *. 3 2: Fig. 8. Infiltration through Sash Perimeter of Window with and without Storm Sash--}4 in. Crack and 14 in. Clearance less than that outside near the ground, and greater near the roof; infil tration will occur at windows in the lower part of the building, and exfiltration at windows in the upper part. Thus in the case of a building200 ft. high, arranged in stories with more or less free communicatioh . from one to another, and with a temperature difference of 70 deg., the . pressure causing infiltration near the ground, and exfiltration near the roof, may easily exceed 0.20 in. of water, which is the equivalent of a twenty-mile wind. The factors influencing the pressures causing infiltration are so numer ous that it does not seem wise at this time to attempt to include any. quantitative values to express the effect of temperature difference,.but it. is something that should be kept in mind in the design'and operationof heating systems in tall buildings. , 68 T a b l e 39. n f il t r a t io n T hrough D o u b le H ung W ood Sash W in d o w s *-*I Chapter 2--Heat Losses from Buildings Practically all leakage around trames can oe stopyeu uy dBSaeeseAd i ronLehaekaatgee,mibsysioHno uo fg h2t4e0n B.t.u. per bq. and Schrader ft(.T ransactio ns , A. S. H. V. E., Vot. 30, 1924, No. 686.)