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138 CHAPTER 10 1959 Guide by parging or a good exterior grade sheatiling paper on the outside of the insulation can be effective in such cases. Vapor which diffuses inwards under cooling conditions adds to the cooling load. Vapor barriers in walls installed for winter conditions are a help in reducing this. However, if condensation does occur on the back of a vapor barrier installed on the inside of the insulation, the latent heat which is then released on the inside of the insulation may add to tire heat gain through the wall. REFERENCES 1 S. C. Hite and J. L. Dray: Research in Home Humidity Control (Purdue University, Engineering Experiment Station Research Series No. 106. November 1948). . * * S. C. Chang and N. B. Hutcheon: Dependence of water vapor permeability on temperature and humidity (ASHAE Transactions, Vol. 62, 1956, p. 437). * F. A. Joy and E. R. Queer: Permeance measurement im proved by special cell (ASHVE Transactions, Vo). 55, 1949, p. 377). 4 F. A. Joy, E. R. Queer, and R. E. Schreiner: Water Vapor Transfer Through Building Materials (Pennsylvania State College, Engineering Experiment Station Bulletin No. 61, December 1948). * J. D. Babbitt: The diffusion of water vapor through vari ous building materials (Canadian Journal of Research, Feb ruary 1939, p. 15). * F. A. Joy and D. R. Fairbanks: Effect of unbalanced air. fressure on permeance (ASHAE Transactions, Vol. 62, 956, p. 451). 1 R. M. Barren Diffusion In and Through Solids (Cambridge Press, London, 1951). 1 L. V. Teesdale: Remedial Measures for Building Construc tion (U. S. Forest Products Laboratory Report R1710, 1947). *F. B. Rowley, A. B. Algren, and C. E. Lund: Methods of Moisture Control and Their Application to Building Construc tion (University of Minnesota, Engineering Experiment Station Bulletin No. 17). s* H. J. Barre: The Relation of Wall Construction to Moisture. Accumulation in Fill-Type Insulation (Iowa State College of Agriculture and Mechanic Arts, Agricultural Experiment Station Bulletin No. 271, 1940). 11 P. F. McDermott: Moisture migration: a survey of theory and existing knowledge (Refrigerating Engineering, August 1941, p. 103). 11 R. I. Wray and A. R. Van Vorst: Permeability of paint films to moisture (Industrial and Engineering Chemistry, Vol. 25, 1933, p. 842). 14 R. R. Britton and R. C. Reichel: Water Vapor Trans mission of Building Materials Using Four Different Testing Methods (U. S. Housing and Home Finance Agency Technical Bulletin No. 12, January 1950). 14 E. R. Bell, M. G. Seidl, and N. T. Krueger: Water-vapor permeability of building papers and other sheet materials (ASHVE Transactions/Vol. 57,1951, p. 287). 11 Value from unpublished texts of Pennsylvania State Col lege Experiment Station. . 14 F. A. Joy: Basic concepts of water vapor migration and their application to frame walls (ASTM Special Technical Pub lication No. 119, 1951, p. 2). n Condensation Control in Dwelling Constructions (U. S. Housing and Home Finanoe Agency; 1949). BIBLIOGRAPHY H. W. Wooley: Moisture Condensation in Building Walls (National Bureau of Standards Report BMS 63, December 14, 1940). F. B. Rowley, A. B. Algren. and C. E. Lund: Condensation of moisture and its relation to building construction and opera tion (ASHVE Transactions, Vol. 45,1939, p. 231). P. D. Close: Permissible relative humidities in humidified buildings (ASHVE Journal Section, Heating, Piping and Air Conditioning, December 1939, p. 766). F. B. Rowley, A. B. Algren, and C. E. Lund: Condensation within walls (ASHVE Transactions, Vol. 44, 1938, p. 95). H. Edenbolm: Moisture movement and moisture distribution in the walls of buildings (Meddelandcn Fran Statens Forskningskommitte for Lantmannabyggnader No. 5, 1945, p. 53, available a3 Technical Translation TT-361 from the National ResearchCouncil of Canada, 1952). J. D. Babbitt: Physics of Condensation in Buildings (Na tional Research Council of Canada Bulletin No. 2). L V. Teesdale: Comparative resistance to vapor transmission of various building materials (ASHVE Transactions, Vol. 49, 1943, p. 124). Durability of moisture-resistant membrane materials in con tact with the ground (Housing and Home Finance Agency, Housing Research No. 4, October 1952, p. 23). Proposed method of test for water vapor transmission of building materials utiiiting the Penn State-Armstrong cell (ASTM Bulletin No. 215, July 1956, p. 63). Heat and water vapor transmission apparatus for insulated panels (National Bureau of Standards, Technical News Bulle tin, November 1954, p. 157). F. A. Joy and A. W. Sherdon: Automatic permeance measure ment by the permeometer (ASHAE Transactions, Vol. 59, 1953, p. 435). F. B. Rowley: A theory covering the transfer of vapor through materials (ASHVE Transactions, Vol. 45, 1939, p. 545). F. G. Hechler, E. R. McLaughlin, and E. R. Queer: Simul taneous heat and vapor transfer characteristics of an insulat ing material (ASHVE Transactions, Vol. 48, 1942, p. 505). J. A. Paxton and N. B. Hutcheon: Moisture migration in a closed, guarded hot plate (ASHVE Transactions, Vol. 58, 1952, p. 301). C. G. Gurr, T. J. Marshall, and J. T. Hutton: Movement of water in soil due to a temperature gradient (Soil Science, November 1952, p. 335). W. A. Hadley and Ray Eisenstadt: Moisture movement in soils due to temperature difference (ASHAE Transactions, Vol. 59, 1953, p. 395). K. R. Solvason: Moisture in transient heat flow (ASHAE Transactions, Vol. 62, 1956, p. 111). H. F. Winterkorn: Fundamental similarities between electroosmotic and thermo-osmotic phenomena (Proceedings S7lh nual Meeting, Vol. 27, Highway Research Board, 1947, p. ). S. C. Chang and N. B. Hutcheon: Performance of desiccants in the dry pan test for water vapor permeance of membranes' (Canadian Journal of Technology, September 1953, p. 175). F. A. Joy: Thermal conductivity of insulation containing moisture (ASTM Special Technical Publication No. 217, Febru ary 1957, p. 65). J. S. Cammerer: The effect of moisture on heat transmission through building and insulating materials (Wdrme und KdlletechnxK, September 1939, p. 126, available as Technical Trans lation TT-317 of the National Research Council of Canada, 1952). H. B. Jesperson: Thermal conductivity of moist materials and its measurement (Journal of IHVE, August 1953, p. 157). D. Krischer: Heat conductivity and water vapor diffusion in materials for insulation against cold (Wdrme und KdltetechniJfc, 1941, 43(0), p. 2, translation available from British Build ing Research Statioo as Library Communication No. 492). D. A. De Vries: The thermal conductivity of soil (Mededelingen van de Landbouwhogeschool te wageningen, 1952, 52(1). p. 1, translation available from British Building Re search Station as Library Communication No. 759). C. H. Johansson: Moisture transmission and moisture dis tribution in building materials (Wdrme-Ventilatione-Sanitetstek, 19 : 67, 1948, available as Technical Translation TT-189 from the National Research Council of Canada). J. D. Babbitt: The movement of moisture through solids (ASTM Bulletin No. 212;February 1956, p. 58). J. R. Philip and D. A. De Vries: Moisture movement in porous materials under temperature gradients (American Geo physical Union Transactions, April 1957, p. 222). CHAPTER II INFILTRATION AND VENTILATION Causes of Infiltration, Infiltration Due to Wind Pressure, Infiltration Due to Temperature Difference, Sealing of Vertical Openings, Infiltration Measurement, Natural Ventilation, Wind Forces, Temperature Difference forces, Heat Removal, Effect of Unequal Openings, Combined Wind and Temperature Forces, Types of Openings; General Ventilation Rules, Ventilation of Animal Shelters, Garage Ventilation INFILTRATION is the air leakage through cracks and of openings on the windward and leeward sides, and on the interstices, around windows and doors, and through lower floors and on the upper floors; and (6) influence of floors and walls. Its magnitude depends on the structural a planned air supply and the related outlet vents. Tight design, workmanship, and condition of the building. The construction is essential for preventing large heat loss due rate of infiltration cannot be controlled by the inhabitants to infiltration. of the building to any. considerable extent. Natural ventila In view of the meager information available on infiltra tion is the controlled displacement of air through openings, tion, a cooperative investigation was undertaken in 1954 in such as windows, doors, and ventilators as well as through which the infiltration rates of residences were obtained by combustion heating devices. actual measurement.1' * In 1956 a study was started at the CAUSES OF INFILTRATION ASHAE Research Laboratory to obtain additional infor mation on infiltration through building entrances.* These .The air leakage which takes place through various aper tures in buildings must be estimated in heating and cooling studies are yielding quantitative information on factors af fecting infiltration rates, but more data are still needed. calculations and enough heating or cooling capacity provided to offset the heat lost or gained by the air leakage. The INFILTRATION DUE TO WIND PRESSURE rate of air flow into and out of a building depends on the The wind causes a pressure to be exerted on one or two magnitude of the pressure difference between the inside sides of a building. As a result, air comes into the building and outside of the structure and on' the resistances presented on the windward side through cracks or porous construction, to this pressure difference. The pressure difference exerted _ and a similar quantity of air leaves on the leeward side on the building walls by the air may be caused either by through like openings. In general, the resistance to air wind or by a difference in density of the air inside and out movement is similar on the windward to that on the leeward side the building. The effect of the wind depends on the side. This causes a building up of pressure within the building, interrelation of the speed and direction of the wind and the and a lesser air leakage than that experienced in single wall exposure of the building. The effect of the difference in the tests as determined in the laboratory. It is assumed that density of the air depends on the magnitude of the indoor- actual building leakages, owing to this building up of pres outdoor temperature difference, the height of the rooms, the sure, will be 80 percent of laboratory test values. While shape of the openings, and their elevation in the room or there are cases where this is not true, tests in actual buildings building. The effect of the difference in density is often re substantiate the factor for the general case. Mechanical ferred to as the chimney or stack effect. The pattern of air ventilating systems are frequently designed to produce flow through any part of the structure depends on both the positive or negative pressures in an enclosure, which are pressure difference and the openings. In general, when the greater or lower than prevalent wind pressures. In such pressure difference is the result of wind pressure, air will designs, if the specified rate at which air is to be supplied enter the building through openings in the windward walls to, or removed from, the enclosure by positive means, ex and leave through openings in the leeward walls or through ceeds the infiltration rate, it is common practice to use the ventilating ducts in the roof. When the pressure difference greater value in determining the heating capacity to warm is caused by the indoor-outdoor temperature difference the the outdoor air. flow will be along the path of least resistance from inlets at lower levels to outlets at higher levels in a heated build Infiltration Through Walls ing or in the opposite direction for an air-conditioned build ing. Data on infiltration/ through brick and frame walls are given in Table l.4 The brick walls listed in this table are An exact estimate of the amount of infiltration under walls that show poor workmanship, and which are con design conditions is difficult to make. The complicating structed of porous brick and lime mortar. For good work factors include (1) variations in building construction, par manship, the leakage through hard brick walls with cement- ticularly as to width of crack or size of openings through lime mortar does not exceed one-third the values given. which air leakage takes place; (2) variations in wind ve These tests indicate that plastering reduces the leakage by locity and direction; (3) exposure of the building with re about 96 percent; a heavy coat of cold water paint, 50 per-' spect to air leakage openings, and with respect to adjoining cent; and three coats of oil paint carefully applied, 28 per buildings; (4) variations in outdoor temperatures which in cent. The infiltration through walls ranges from 6 to 25 fluence the chimney effect; (5) relative area and resistance percent of that through windows and doors in a 10-story 139