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200 CHAPTER 9 1954 Guide h 6 A.S.H.V.E. Research Report No. 869--Surface Conductances as Affected by Air Velocity, Temperature and Character of Surface, by F. B. Rowley, A. B. Algren and J. L. Blackshaw (A.S.H.V.E. Transactions, Vol. 36, 1930, p. 444). 7 Forced Convection Heat Transfer from Flat Surfaces, by G. V. Parmelee and R. G. Huebscher (A.S.H.V.E..Research Bulletin, No. 3, p. 40; also published in A.S.H.V.E. Transactions, Vol. 53,1947, p. 276). 8 A.S.H.V.E. Research Report No. 1399--Heat Flow through Unshaded-Glass: Design Data for Load Calculations, by G. V. Parmelee and W. W, Aubele(A.S.H.V,.E. Transactions, Vol. 56; 1950, p. 371). .' 9 Radiation and Convection Across Air Spaces in Frame Construction, by G. B. Wilkes and C. M. F. Peterson (A.S.H.V.E. Transactions, Vol. 43,1937, p. 351). 10 Thermal Test Coefficients of Aluminum Insulation for Buildings, by G. B. Wilkes, F. G. Hechler and E. R. Queer (A.S.H.V.E. Transactions, Vol. 46j,1940, p. 109). 11 Effect of Studs and Joists on Heat Flow Through Frame Walls and Ceilings, by Paul D. Close {Heating, Piping and Air Conditioning, October, 1943, p. 529). 11 A.S.H.V.E. Research Report No. 1213--Heat Loss Through Basement Walls 1and Floors, by F. C. Houghten, S. I. Taimuty, Carl Gutberlet and C. J. Brown (A.S.H.V.E. Transactions, Vol. 48, 1942, p. 369). 18 Measurements of Heat Losses from Slab Floors, by R. S. Dill, Wm. C. Robinson Sand H. E. Robinson {National Bureau of Standards, Building Materials and Structures Report BMS 103). 14 See pp. 130-132 of Reference 7. 15 Heat Transmission through Glass, by G. V. Parmelee (A.S.H.V.E. Research - Bulletin No. 1, July 1947). BIBLIOGRAPHY ; A.S.H.V.E. Research Reports: ^ No. 852--Effects of Air Velocities on Surface Coefficients, by F. B. Rowley, A. B. Algren and J. L. Blackshaw (A.S.H.V.E. Transactions, Vol. 36,1930, p..123). . f No. 895--Wind Velocity Gradients Near a Surface aud Their Effect on Film Conductance, by F: C. ? Houghten and Paul McDermott (A.S.H.V.E. Transactions, Vol. 37, 1931, p. 301). ; No. 914--Surface Coefficients as Affected by Direction of Wind, by F. B. Rowley and W. A. Eckley -* (A.S.H.V.E. Transactions, Vol. 38, 1932, p. 33). .. No. 915--Conductivity of Concrete, by F. C. Houghten and Carl Gutberlet (A.S.H.V.E. Transac- ' tions, Vol. 38, 1932, p. 47). No. 964--The Heat Conductivity of Wood at Climatic Temperature Differences, by F. B. Rowley (A.S.H.V.E. Transactions, Vol. 39, 1933, p. 329). No. 996--Insulating Value of Bright Metallic Surfaces, by F. B. Rowley (A.8.H.V.E. Transactions, \ Vol. 40, 1934, p. 413). No. 1026--Thermal Properties of Concrete Construction, by F. B. Rowley, A. B. Algren and Clifford Carlson (A.S.H.V.E. Transactions, VoL 42, 1936, p. 33). No. 1048--Thermal Properties of Concrete Construction, by F. B. Rowley, A. B. Algren and Robert Lander (A.S.H.V.E. Transactions, Vol. 43, 1937, p. 33). No. 1351--Overall Coefficients for Flat Glass Determined under Natural Weather Conditions, by G. V. Parmelee and W. W. Aubele (A.S.H.V.E. Transactions, Vol.;55,T949,` p. 39): i Insulating Effect of Successive Air Space Bounded by Bright Metallic Surfaces," by L:;W; Schad \ (A.S.H.V.E. Transactions, Vol. 37, 1931, p. 285). Thermal Conductivity of Wood, by J. D. MacLean (A.S.H.V.E. Transactions, Vol:47, 1941, p; 323). The Specific Heat of Thermal Insulating Materials, by G. B. Wilkes and C. O. Wood (AiS:H;V.E. Trans- j actions, Vol. 48, 1942, p. 493). I Heat Loss Studies in Four Identical Buildings to Determine the Effect of Insulation, by D. B. Anderson i (A.S.H.V.E. Transactions, Vol. 48, 1942, p. 471). Effect of Ceiling Insulation upon Summer Comfort, by T. D. Phillips (Notional Bureau of Standards, Report BMS52, July 1, 1940). .; Thermal Insulation Made of Wood-Base Materials, Its Application and Use in Houses, by L. V: Teesdale J (U. S. Forest Products Laboratory Report No. R1740, October 1949). ' Heat Transmission Through Building Materials, by F. B. Rowley and A. B. Algren (University of Minns- sota. Engineering Experiment Station Bulletin No. 8). K Building Insulation, by P. D. Close (American Technical Society, Chicago, 1945). , ; a* CHAPTER 10 WATER VAPOR AND CONDENSATION IN BUILDING CONSTRUCTION Basic Principles, Visible Condensation, Vapor Transmission Through Materials, Permeance Data and Testing, Concealed Condensation in Heated. Buildings, Control of Concealed Condensation, Condensation in Cooled Structures ATER as a vapor is present in all air and as adsorbed moisture in Wbuilding materials such as wood. Even dense materials like glass hold considerable adsorbed moisture on their surfaces. In each of these places water may be harmless or even, desirable, if its quantity is not ex cessive. Excessive moisture in building materials may cause mold, rot, and rust. Water, blistering may. damage seriously the exterior, paint on wood siding when the sidmg moisture content rises above a safe level. While excessive moisture in building materials may be caused by rain leak age, it frequently is due.to .water vapor migration, a phenomenon likely to be associated with a temperature difference. Thus it may occur in the walls and roofs of heated' buildings in winter, and in the enclosure of re frigerated spaces at all seasons. Water vapor released within a building, either incidentally or intentionally, may result in excessive moisture in the structure. . The behavior of water vapor is too often overlooked or given scant con-, sideration in the design and construction of buildings and in the layout of air conditioning processes. It is an important factor to consider in the construction of residences arid public buildings in cold climates and to a lesser extent in warm climates. It is extremely important to consider the moisture problem in the construction of cold storage and low temperature rooms. ' Manufacturing processes which demand a high humidity, require buildings designed to reduce the effect of moisture on the structure. Moisture problems in residences occur in winter and becoine increasingly important as homes are built smaller and tighter. Water vapor originates from such necessary living requirements as cooking, laundering, bathing and the breathing and perspiration of people. In a typical family of four, the average daily production of water vapor from these sources may be as much as 25 lb, and may be much greater where such appliances as humidi fiers, automatic washers and dryers are used.1 Another large source of water vapor is sometimes the bare earth in a crawl space or basement. All this water vapor must escape from the dwelling. BASIC PRINCIPLES Water vapor in air is a gas which occupies all the space and has the same properties that it would have if the (dry) air were not present. It is steam at a low temperature and pressure. Generally it is superheated, *-e-i not saturated. When water vapor is saturated, the space (or air) holds all the water vapor that it can at the existing temperature, and its vapor pressure is a maximum. A smaller content of water vapor produces >s vapor pressure. The ratio of this pressure to the saturation pressure flt the given temperature is called the relative humidity of the space. If an air-vapor mixture at a given relative humidity is cooled, its vapor Pressure is unchanged but its relative humidity increases until at some 201