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404 CHAPTER 22 ties gradients near a surface their effect on film conduct* ance (A5HVE Transactions, Vol. 37,1931, p. 301). No. 914--F. B. Rowley and W. A. Eekley: Surface ooefEdenta as affected by direction of wind (ASHVE Transactions, VoL 38, 1932, p. 33). No. 915--F. C. Houghten and Carl Gutberlet: Conductivity of ooncrete (ASHVE Transactions, VoL 38, 1932, p. 47). No. 964--F. B. Rowley: The heat conductivity of wood at dimatie temperature differences (ASHVE Transactions, VoL 39, 1933, p. 329). No. 966--F. B. Rowley: Insulating value of bright surfaces (ASHVE Transactions, VoL 40, 1934, p. 413). No. 1026--F. B. Rowley, A. B. Algren, and Clifford Carlson: Thermal properties of concrete construction (ASHVE Trans actions, Vol 42, 1936, p. 33). No. 1048--F. B. Rowlfty, A. B. Algren, and Robert Lander: Thermal properties of concrete construction (ASHVE Trans actions, VoL 43, 1937, p. 33). No. 1351--G. V. Parmfilee and W. W. Aubeie: Overall coeffi cients for flat dass determined under natural weather condi tions (ASHVE Transactions, VoL 55,1949, p. 39). M. E. Stephenson and M. Mark: Thermal conductivity of porous materials (ASHRAE Transactions, VoL 67.. 1961, p. 170). J. D. MacLean: Thermal conductivity of wood (ASHVE Transactions, Vol 47, 1941, p. 323). G. B. Wilkes and C. O. Wood: The specific heat of thermal insulating materials (ASHVE Transactions, VoL 48, 1942, ps D. B. AndeiBon: Heat loss studies in four identical buildings to determine the effect of inmlntirm (ASHVE Transactions. VoL 48, 1942, p. 471). F. B. Rowley and A. B. Algren: Heat Transmission Through Building Materials (University of Minnesota, Engineering Ex periment Station Bulletin No. 8, p. 11). T. D. Phillips: Effect of Ceiling Insulation upon' Summer Comfort (National Bureau of Standards Report BMS52, July 1, 1940). R. M. lender: Factors Affecting Thermal Conductivity (Uni versity of Minnesota, Engineering Experiment Station Technical Paper No. 49, July 1944). J- G. Macormack: Metal type reflective ingulottnuf prove themselves (Refrigerating Engineering, Seotember 1949. d 885). 'V O. R. Melntire and D. W. McCuaig: Styrofoam--a new ther mal insulation (Refrigerating Engineering, September 1946 P- 217). ^ - J. D. Verschoor and Paul Greebler: Heat transfer by gas con duction and radiation in fibrous insulation (ASME Transactions. 1952, p. 961). G. B. Wilkes: Heat Insulation (John Wiley & Sons, New York. 1950). ^N G. B. Wilkes, F. G. Hechter, and E. R. Queer: Thermal test coefficients of aluminum insulation for buildings (ASHAE Transactions, Vol. 46, 1940, p. 109). F. A. Joy: Improving attic space jugulating values (ASHAE Transactions, VoL 64, 1958, p. 251). F. C. Houzhten, 8. L Taimuty, Cari Gutberlet, and C. J. Brown: ASHVE Research Report No. 1213--Heat loss through basement walls and floors (ASHVE Transactions, VoL 48, 1942, p. 369). R. S. Dill, W. C. Robinson, and H. E. Robinson: Measure ments of Beat losses from Slab Floor* (National Bureau of Standards, Building Materials and Structures Report BMS 103). G. V. Parmelee: Heat Transmission through Glass (ASHVE Research Bulletin No. 1, July 1947). ASTM Standards on Thermal Insulating Materials (American Society of Testing Materials, Philadelphia, 1957). R. J. Fabian: Thermal nml(jni sign Engineering, March 1958). (Materials tn De W. P. Ellis: Surfadngs for glass fiber and foam ttwmwl insula tion (Heating, Piping and Air Conditioning, July 1958, p. 136). G. B. Wilkes and C. M. F. Peterson: Radiation and convec tion across, air spaces in frame construction (ASHVE Trans actions, VoL 43, 1937, p. 351). 1965 Guide And Data Book L. W. Schad: Insulating effect of successive air space branded by bright metallic surfaces (ASHVE Transactions, Vol 37, 1931, p.285). F. C. Hooper and W. J. Mores: The Influence of Aging Factors on the Emissuriiy of Reflective Insulations (ASTM Bulletin No. 182, May 1952, p. 182). L. F. Miller: The effect of moisture on beat transmission in insulating materials (Refrigerating Engineering, November 1927, p. 141). H. E. Robinson, L. A. Cosgrove, and F. J. Powell: Thermal Resistance of Airspaces and Fibrous Insulations Bounded by Re flective Surfaces (National Bureau of Standards, Building Ma terials and Structures'Report BMS 151). N. B. Hutcheon: Vapor problems in thermal insulation (Heating, Piping and Air Conditioning, August 1958, p. 150). H. C. Brown, Jr., and L. E. Bish: Effect of convection and moisture deposition on beat transmission through cold storage test walls (Refrigerating Engineering, January 1954, p. 62). C. F. Kayan and R. G. Gates: Tnflmwn of mgnlatinn on moisture-condensation aspects of steel-framed cold-storage ware house structure (Refrigerating Engineering, January 1958. p.39). ^ H. M. Whippo and B. T. Arnberg: Survey and Analysis of. the Vapor Transmission Properties of Building Materials (U. S. De partment of Commerce, Office of Technical Services PB131219, January 1955). Paul D. Close: Building Insulation (American Technical Society, Chicago, 1951, 4th ed.). L. V. Teesdale: Thermal Insulation Made of Wood-Base Materials, Its Application and Use Houses (U. S. Forest Products Laboratory Report No. R1740, October 1949). T. S. Rogers: Design ofInsulated Buildings for Various Climates (F. W. Dodge Corp., New York, 1951). Ray Thomas: Thermal insulation for industrial requirements (Petroleum Refiner, January, February, March, June, July, Au gust, October, November 1952; January, February 1953). W. S. Woodaide: Cold room insulations (Refrigerating Engineering, September 1948, p. 223). R. H. Kropschot: Cryogenic insulation (ASHRAE Journal, September 1959, p. 48). V. DiMaio et al: Summary of ASRE domestic refrigerator engi neering conference on insulation (Refrigerating Engineering, September 1950, p. 857). W. F. Hopper: Method of measuring the odor absorption and' retention, properties of surfaces (ASHRAE Transactions, Vol 65,1959, p. 735). Stcmdard Methodfor Measurement ofOdor in Atmosphere (Dilu tion Method) (ASTM Standard D-1391-57). . W. F. Kerka and C. M. Humphreys: ASHAE Research Report No. 1547--humidity effect on odor perception (ASHAE Transactions, Vol. 62,1956, p. 531). R. W. Penney and R. F. Guilfoy: Laboratory Tests ofRefrigera-tor Car* for Perishable Foods (Agricultural Marketing-Research Report No. 365, USDA, September 1959). M. V. Gerrity and H. D.- Johnson: Motortruck Transportation of Freshly Killed Beef (Marketing Research Report No. .119, USDA, June 1956). H. D. Johnson and P. L. Breakiron: Protecting Perishable Foods During Transportation by Truck (Agriculture Handbook No. 105, USDA, December 1956). H. D. Johnson and M. W. Gerritv: Report of Tests on Trans portation of Frozen Poultry with Mechanically Refrigerated Trucks (an interim report) (AMS-144, USDA, May 1952). C. W. Phillips, P. R. Achenbach, and R. W. Penney: Cooling Loads of Refrigerated Trailer* (Technical New* Bulletin, National Bureau of Standards, October 1958). W. H. Redit et al: Transportation of Frozen Citrus Concentrate by Railroad and Motortruck from Florida to Northa-n Markets (Agricultural Information Bulletin No. 52, USDA, June 1951). H. D. Strong: The Proper Selection of Refrigeration and Heating Equipment for Protective Transporation Bodies (8AE Paper No. 11, Society of Automotive Engineers, January 1957). CHAPTER 23 MOISTURE IN BUILDING CONSTRUCTION Properties of Water in Air; Wafer m Building Materials; Vapor Transmission; Permeance and Testing; Visible Condensation; Concealed Condensation in Heated Buddings; Control of Concealed Condensation; Condensation in Cooled Structures THE behavior of moisture is too often overlooked or given relative humidity, is represented by point A. This is a condi scant attention in the design and construction of build tion of partial saturation; Le., less than 100 percent relative ings. It is present as a vapor in all air and as adsorbed mote-humidity. The vapor pressure of the water present in the air, tore in m1^- building materials. It may also be present at although not shown on the chart, can be calculated readily times in the free liquid state or as ice in the solid state, within from the vapor pressure at saturation and the relative hu the range of temperatures encountered in many buildings. midity, since relative humidity is equal to the ratio of the Problems involving moisture may arise from changes in mois actual vapor pressure to the saturation pressure at the existing ture content, from the presence of excessive moisture, or from effects associated with its changes in state. Of particular interest is the change from the vapor to the liquid or solid state, known as condensation. This may be with a reduction of temperature with time, or temperature. The increasing relative humidity accompanying cooling from the condition represented by A on the chart to point B can readily be followed. At B, however, at 44.6 F, the relative humidity becomes 100 percent, and the air-vapor mixture is may occur as a result of migration of water vapor to regions of lower temperature. Moisture problems involving condensa to be saturated. The temperature at which this particu lar air-vapor mixture, upon cooling, becomes saturated is its tion are therefore most likely to occur in buildings in any climate in which there is a source of water vapor at tempera dew-point temperature. Upon further cooling, to 35 F, the original amount of water vapor can no longer be retained and tures above normal, or in cooLed structures, -and in buildings is reduced, in this case, to the condition represented by C, in cold climates. from 0.0633 lb per lb dry air to 0.0427 lb per lb dry air. The Most moisture problems in residences occur in winter and process ABC is typical of that which an air-vapor mixture become increasingly important as homes are built smaller and tighter. Water vapor originates from such necessary living experiences when it comes in contact with a cool window surface.' Cooling from B to C results in visible condensation requirements as cooking, laundering, bathing, and the breath- on the glass surface. If the point C were below 32 F, the con ing and perspiration of people. In a typical family of four, densation would be in the form of frost. the average daily production of water vapor from these sources Once the temperature drops below the dew point, or frost may be as much as 25 lb, and may be much greater where such point if below 32 F, the vapor pressure at the condensing appliances as humidifiers, automatic washers, and dryers surface is also reduced, thereby establishing a gradient of are used.1 Another large source of water vapor is sometimes the bare earth in a crawl space or basement. Also, in new construction, moisture is added by poured concrete slabs, masonry construction and new plaster. All this water vapor must escape from the dwelling. vapor pressure from the room air to the window surface. This' gradient will operate, in conjunction with the convective ac tion within the room, to move water vapor continuously to the window surface to be condensed, so long as the concentra tion of water vapor in the room is maintained; PROPERTIES OF WATER VAPOR IN AIR A common winter process is that shown by DE, showing air at 20 F, saturated, being heated-to 70 F with a resulting Water vapor in air is a gas which occupies all the space, along with the air present. In many ways, the water vapor can act independently of the air, since in general its proper ties do not depend on the presence of the air. It exerts its own vapor pressure, and can move about through air in a space, or move through materials under differences in its own vapor pressure, independently of the air. However, when the air is moved suddenly or is heated or cooled, the water vapor pres ent is similarly affected, so that it is usually necessary to con sider it as a part of an air-vapor mixture. The properties of mixtures of air and water vapor are rela tively well known and are in Chapter 3. Changes in these properties with beating and cooling can be followed readily with the aid of a psychrometrie chart, shown in out line in Fig. 1. The saturation line represents the limiting con centrations of water vapor which can exist as vapor at various temperatures. A common condition inside buildings, 70 F and 40 percent vd MoCtstntier*rtBl aremxepncic. sibtiitr (or Iht* cfanMar is to TC 2.4. fcsuhtlioa Fig. .1 .... Two Typical Heating and Cooffng Processes in Air within Buildings Shown on Psydtrocnetric Chart. 405