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Heating Ventilating Air Conditioning Guide 1938 arbitrary rule is to increase the heating surface on floors above neighboring buildings by an amount ranging from 5 per cent to 20 per cent. This extra heating surface is required only on the windward side and on windy days, and hence automatic temperature control is especially desirable with such installations. In stair-wells that are open through many floor levels although closed off from the remainder of each floor by doors and partitions, the strati fication of air makes it advisable to increase the amount of heating surface at the lower levels and to decrease the.amount at higher levels even to the . point of omitting all heating surface on the top several floor levels. One rule is to calculate the heating surface of the entire stair-well in the usual way and to place 50 per cent of this in the bottom third, the normal amount in the middle third and the balance in the top third. HEAT EQUIVALENT OF AIR INFILTRATION Sensible Heat Loss The heat required to warm cold outside air, which enters a room by infiltration, to the temperature of the room is given by the equation: where Hs = 0.24 Q d (ti -- to) (3) HB = heat required to raise temperature of air leaking into building from to to ft Btu per hour, 0.24 = specific heat of air. Q = volume of outside air entering building, cubic feet per hour, d = density of air at temperature to, pounds per cubic foot, ti = room air temperature, degrees Fahrenheit, = outside air temperature, degrees Fahrenheit. Latent Heat Loss When it is intended to add moisture to air leaking into-a room for the maintenance of proper winter comfort conditions, it is necessary to determine the heat equivalent to evaporate the required amount of water vapor, which may be calculated by the equation: < where Hi = heat required to increase moisture content of air leaking into building from M0 to Mi, Btu per hour. Q = volume of outside air entering building, cubic feet per hour. d = density of air at temperature ti, pounds per cubic foot. ,' Mi = vapor density of inside air, grains per pound of dry air. M0 = vapor density of outside air, grains per pound of dry air. L = latent heat of vapor at Mi, Btu per pound. It is sufficiently accurate to used = 0.075 lb, in which case equation 3 reduces to 5 and if the latent heat of vapor is assumed for general condi tions as 1060 Btu per pound equation 4 reduces to 6. Hs = 0.018 Q (k -- h) Hi = 0.0114 Q (Mi - M0) (5) (6) While a heating reserve must be provided to warm inleaking air on the windward side of a building, this does not necessarily, mean that the 130 Chapter 6. Air Leakage heating plant must be provided with a reserve capacity, since the inleaking air, warmed at once by adequate heating surface in exposed rooms, will move transversely and upwardly through the building, thus relieving other radiators of a part of their load. The actual loss of heat of a building, caused by infiltration is not to be confused with the necessity for pro viding additional heating capacity for a given space. Infiltration is a disturbing factor in the heating of a building, and its maximum effect (maximum in the sense of an average of wind velocity peaks during the heating season above some reasonably chosen minimum)must be met by a properly distributed reserve of heating capacity, which reserve, how ever, is not in use at all places at the same time, nor in any one place at all times. REFERENCES Air Leakage, by F. C. Houghten and C. C. Schrader (A.S.H.V.E. Transactions, Vol. 30, 1924, p. 105). Air Leakagearound Window Openings, by C. C. Schrader (A.S.H.V.E. Transactions, Vol. 30, 1924, p. 313). Neutral Zone in Ventilating, by J. E. Emswiler (A.S.H.V.E. Transactions, Vol. 32, 1926, p. 59). Infiltration through Plastered and Unplastered Brick Walls, by F. C. Houghten and Margaret Ingels (A.S.H.V.E. Transactions, Vol. 33, 1927, p. 377). Effect of Frame Calking and Storm Sash on Infiltration around and through Windows, by W. M. Richtmann and C-. Braatz (A.S.H.V.E. Transactions, Vol. 34, 1928, p. 547). Air Leakage on Metal Windows in a Modern Office Building, by F. C. Houghten and M. E. O'Connell (A.S.H.V.E. Transactions, Vol. 34, 1928, p. 321). The Weathertightness of Rolled Section Steel Windows, by J. E. Emswiler and W. C. Randall (A.S.H.V.E. Transactions, Vol. 34, 1928, p. 527). Air Leakage through a Pivoted Metal Window, by F. C. Houghten and M. E. O'Connell (A.S.H.V.E. Transactions, Vol. 34, 1928, p. 519). Air Infiltration through Various Types of Brick Wall Construction, by G. L. Larson, D. W. Nelson and C. Braatz (A.S.HiV.E. Transactions, Vol. 35, 1929, p. 183). Pressure Differences across Windows in Relation to Wind Velocity, by J. E. Emswiler and W. C. Randall (A.S.H.V.E. Transactions, Vol. 36, 1930, p. 83). Air Infiltration Through Various Types of Wood Frame Construction, by G. L. Larson, D. W. Nelson and C. Braatz (A.S.H.V.E. Transactions, Vol. 36, 1930, p. 99). Air Infiltration Through Double-Hung Wood Windows, by G. L. Larson, D. W. Nelson and R. W. Kubasta (A.S.H.V.E. Transactions, Vol. 37, 1931, p. 571). Flue Action in Tall Buildings, by H. L. Alt (Heating, Piping and Air Conditioning, May, 1932). ... Air Infiltration Through Steel Framed Windows, by D. O. Rusk, V. H. Cherry and L. Boelter (Heating, Piping and Air Conditioning, October, 1932). Investigation of Air Outlets in Class Room Ventilation, by G. L. Larson, D. W. Nelson and R. W. Kubasta (A.S.H.V.E. Transactions, Vol., 38, 1932, p. 463). Influence of Stack Effect on the Heat Loss in Tall Buildings, by Axel Marin (A.S.H. V.E. Transactions, Vol. 40, 1934, p. 377). Wind Velocities Near a Building and Their Effect on Heat Loss, by F. C. Houghten, J. L. Blackshaw, and Cart Gutberlet (A.S.H.V.E. Transactions, Vol. 40, 1934, p. 387). 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). Infiltration Characteristics of Entrance Doors, by A. M. Simpson (Refrigerating Engineering, June, 1936). Heating Requirements of an Office Building as Influenced by the Stack Effect, by F. C. Houghten and Carl Gutberlet (AiS.H.V.E. Journal Section, Heating, Piping and Air Conditioning, July, 1937). 131 /