One of the inconveniences that results from the recommended relative humidity for comfort and health is condensation. Mr. Howard T. Fisher discusses remedies for condensation. He states in the following paragraphs taken from his article "The Country House":1

.... With well-insulated walls, however, condensation will occur only on the windows, where it can be taken care of, or even largely eliminated except during the coldest weather.

There is nothing inherently objectionable to condensation. In fact, to those persons who appreciate the comfort of a high humidity its presence is a pleasing indication that there is probably at least a fair amount of moisture in the atmosphere. Condensation is, however, the cause of two just complaints: Windows covered with condensation cannot be seen through, and when the surplus moisture of condensation runs down off the glass it forms pools of water on the sills which may stain the curtains and walls. The latter objection can be entirely removed by the provision of adequate condensation gutters to carry off this water. Both objections can be reduced to a minimum by the use of double glazing. In addition to largely preventing condensation this has the further advantage that it reduces the total air infiltration and heat loss from the building, thus saving fuel. Charts prepared by the University of Illinois show that with an inside temperature of 69° and a humidity of 60 per cent condensation will occur on single glass when the outside temperature is only 480, but will not occur on double glass until the temperature is as low as 190. Or, expressing this differently, with an outside temperature of 200 condensation will occur on single glass when the humidity reaches 30 per cent, but will not occur on double glass until it reaches 60 per cent. Even with zero weather outside double glazing will permit a humidity of approximately 50 per cent unaccompanied by any condensation whatever. The ultimate solution to the problem of condensation as well as heat loss may be found in the vacuumized window pane.

1 In Architectural Record, November, 1930.

Double glazing can be accomplished in a variety of ways, but the most important requirement is air-tightness. Both sheets of glass may be set permanently in the same frame, but in this case the glazing should be done during weather as dry as possible. For greatest efficiency the air space between the glass should not be less than one inch in thickness. Even if the glazing is relatively air-tight, dirt will eventually filter in and the glass will require cleaning, which will be difficult to accomplish unless provision is made for the easy removal of the glass. Where such double glazing is contemplated in connection with steel sash it should be remembered that moisture may condense on the interior surface of the metal even if the glass is double. It will usually be found more satisfactory to provide entirely separate frames and glass, placed either inside or outside of the regular window, and stored during the summer. These can be made completely interchangeable with the screens, the same hinges or fasteners being used for both and the putting up of the screens and taking down of the winter sash accomplished at one operation. In order to get as air-tight a fit as possible it may be worth while to use weather-stripping, perhaps of the cloth-lined variety.

Summary

The first consideration in satisfactory house heating is a good structure. The two general types of heating are direct and indirect systems. Most systems are capable of heating a house to 700 at the breathing line, but there is often in cold weather a great difference between the breathing-line temperature and the floor temperature. Experience has shown that the cheaper the heating system the greater the air-temperature difference between floor and ceiling. There is considerable difference in cost of equipment and cost of installation of the various heating systems but the cost of operation, providing the same fuel is used, varies little. The selection of a type of heating depends upon the individual home-owner, the house, and its location.

According to scientific research and experimentation the average home temperature should be 630 or 64° with the proper amount of humidity. By relative humidity is meant the ratio of the amount of moisture present in a given volume of air to the amount required to saturate this volume at the existing temperature. By ventilation is meant the natural or mechanical replacement of vitiated air by fresh air.

References

American Oil Burner Association. Handbook Of Domestic Oil Heating. New York: The Association, 1928. American Society of Heating and Ventilating Engineers. The A.S.H. V.E.

Guide, 1931. New York: The Society, 1931.

Particularly useful for reference. Contains chapter on ventilation standards.

Boyd, D. K. "Designing and Planning for Home Heating Economies," Transactions of the American Society of Heating and Ventilating Engineers, Vol. XXXI (1925). Day, V. S. Warm Air Heating for Residences. Columbus, Ohio: National Warm Air Heating Association, 1930. Pp. 15. Fansler, P. E. "Heating the Small Home," Small Home, September, 1929-July, 1930.

______House Heating with Oil Fuel. New York: Heating and Ventilating Magazine Co., 1927. Fisher, Howard T. "The Country House," Architectural Record, LXVIII (November, 1930), 363-85.

Heating and air conditioning, fuels, humidification, condensation, domestic hot-water supply (pp. 372-84).

Good Housekeeping Institute. Heating the American Home. Household Engineering Series. New York: Good Housekeeping, n.d. Pp.12.

______Selecting and Installing an Oil Burner. Household Engineering Series. New York: Good Housekeeping, 1925. Pp. 16.

Heilman, R. H. "Heating of the Home," Science for the Home Manager. Radio Pub. 48. Pittsburgh: University of Pittsburgh, 1929. Pp. 89-97.

House Beautiful Building Annual, 1926. (Out of print.) Boston: Atlantic Monthly Press, 1926. General principles of heating, fuels, hot-water systems, and insulation (pp. 108-10).

Huntington, Ellsworth. Weather and Health. Bull. 75. Washington: National Research Council of the Academy of Sciences, 1930. Pp. 161.

King, Alfred G. 500 Plain Answers to Direct Questions on Steam, Hot Water, Vapor and Vacuum Heating. New York: Norman W. Henley Publishing Co., 1923.

_______Heating of Residences and Small Buildings. Chicago: Domestic Engineering Publications, 1924.

Martindale, E. S. Humidity in House Heating. Ottawa, Canada: Dominion Fuel Board, 1930. Pp. 38.

Phelan, Vincent B. The Care and Repair of the Home. Garden City, N.Y.: Doubleday, Doran & Co., 1931. Heating and ventilating (pp. 134-57).

Sayers, R. R., and Davenport, Sara J. Review of Literature on the Physiological Effects of Abnormal Temperatures and Humidities. U.S. Dept. of the Treasury, Reprint 1150 from "Public Health Reports." Washington: Government Printing Office, 1927. Pp. 63.

Starbuck, Robert M. Questions and Answers on the Practice and Theory of Steam and Hot Water Heating. Hartford, Conn.: R. M. Starbuck & Sons, Inc., 1927. Suitable for reference on steam and hot-water heating.

Taber, Clarence W. The Business of the Household. Philadelphia: J. B. Lip-pincott Co., 1926. Methods of heating and fuels (pp. 152-92).

U.S. Bureau of Mines:1

How To Improve the Hot-Air Furnace (Technical Paper 208).

Natural-Gas Manual for the Home (Technical Paper 325).

Saving Fuel in Heating a House (Technical Paper 97).

Waste and Correct Use of Natural Gas in the Home (Technical Paper 257).

U.S. Bureau of Public Roads. Construction of Chimneys and Fireplaces. U.S. Dept. of Agriculture, Farmers' Bull. 1649. Washington: Government Printing Office, 1930. Pp.18.

_______The Domestic Oil Burner, by Arthur H. Senner. U.S. Dept. of Agriculture, Circ. 405. Washington: Government Printing Office, 1930. Pp. 29.

_______Operating a Home Heating Plant. U.S. Dept. of Agriculture, Farmers'

Bull. 1194. Washington: Government Printing Office, 1928. Pp. 18.

U.S. Bureau of Standards. List of Publications and Articles Relating to Home Heating Problems. Mimeographed Letter Circ. 284. Washington: The Bureau, 1930.

_______Materials far the Household. Circular of the Bureau, No. 70. Washington: Government Printing Office, 1917. Pp. 259.

1 Publications to be obtained from the Government Printing Office, Washington, D.C.

U.S. Bureau of Standards. Measurements for the Household. Circular of the Bureau of Standards, No. 55. Washington: Government Printing Office, 1915. Pp. 149. Heating value of fuels, comparison of heat insulators (pp. 55-64).

Walsh, Harold Vandervoort. Construction of the Small House. New York: Charles Scribner's Sons. 1923.

Discusses hot-air systems including furnaces with and without flues; steam, one-and two-pipe furnace, vapor-vacuum system, and hot-water systems; also methods used in calculating required size of heater (pp. 109-20).

For information on insulation and heat-proofing see references following the chapter on "Building Materials and Common Construction Practices."