A few years ago Professor Harold Clark of Columbia University completed an environment study which included visits to over 40 countries. Upon his return he told university students that he found hardly one instance of a private dwelling designed to suit its environmental climate. He deplored the fact that practically all modern dwellings throughout the world are patterned after the box-like European houses which fit the cold European climate. If Professor Clark could have conducted his environment study a few centuries ago, however, I am sure that his concluding observations would have been more favorable. For the indigenous and often primitive architectural forms of that time had become adjusted to local climate through a long process of trial and error.
Architecture these days ignores environment. Witness the growth of the world’s cities, which violate natural principles of summer cooling. Contrast the cool, shady meadow found in nature with the exposed acres of urban pavement, concrete buildings, and reflecting roof-tops. Compatibility of the building to its environment is currently neglected as modern designers devote a disproportionate amount of attention to appearance and fashion — which, of course, boost the sale value of the package.
Corrected Effective Temperature
Owing to the extensive use made of climatic averages in describing regional climate conditions, there is a widespread tendency to regard climate as uniform in respect to each latitude and each season. In dealing with actual climate, however, and especially in relation to building design, nothing could be farther from the truth. The old health-food adage, “a carrot is not a carrot” (comparatively, in food-value content), holds true in the meteorological field as well. That is, “temperature is not temperature”; human reactions to temperature depend upon the ability of the body to lose heat to the surroundings by convection to the air, by radiation to the surrounding surfaces and by evaporation of moisture from the skin. Body reactions therefore depend not only on the temperature of the air but also on its humidity and rate of movement as well as the mean (or average) radiant temperature of the surrounding surfaces.
It is utter nonsense to talk of a “72-degree Design Temperature.” A dry bulb of 72 degrees Fahrenheit temperature at 90 percent relative humidity with a 10-foot-per-minute air movement will convey the same effective temperature as a 100-degree bulb at a 10 percent humidity and a 100-foot-per-minute air movement. In both instances, the combination of meteorological factors will produce an effective temperature of 80 degrees in a room where the walls, floor, and ceiling are at the same temperature as the air. When the surrounding surfaces are not at air temperature, an altogether different temperature index is employed to measure the actual meteorological conditions. This “adjusted” index is called the Corrected Effective Temperature (C.E.T.).
Three Basic Principles of Building Climatology
The three basic climate relationships should accordingly be kept in mind. This will prove most helpful in cooling or heating the owner-designed, owner-built home. Here they are:
1) Temperature is related to effective humidity. As temperature rises, relative humidity drops. When high temperatures combine with high humidity, the body has difficulty in perspiring and acute discomfort is experienced.
2) Air temperature is related to average radiant (or surface) temperature. In order to keep the body in an optimum-comfort zone under low air temperature conditions, the radiant temperature must be kept high. And in summer, when the air temperature is high, a low radiant temperature is required.
3) Air movement is related to both temperature and humidity. Up to a certain point, high temperatures can be counteracted by air movement.
After discovering a way to incorporate the foregoing climatological principles into a single index, the American Society of Heating and Ventilating Engineers produced the Effective Temperature Scale. Even the effective temperature scale has its limitations in terms of actual body comfort. For instance, cold concrete floors in a room of otherwise comfortable effective temperature will produce discomfort due to vasoconstriction of the feet. If the feet lose heat rapidly from contact with a cold floor, a person will experience discomfort even though the “official” effective temperature is within the “comfort” zone. Conversely, it is possible to feel warm in a relatively cool room if seated with feet out-stretched in front of an open fire. A high ceiling temperature, also in a “comfortable” effective temperature range, will produce uncomfortable effects. And it makes a difference to body cooling whether the wind movement is directed onto back or onto the face — the latter having much more influence on body comfort or discomfort.
While designers and home builders continue their relentless defacement of the landscape over the world — from the Middletown, U.S.A., Tract Development to “Housing for the Urban Bantu” in South Africa — the research student can locate only a score of counteracting influences in laboratories throughout the world. But from these few agencies we can surely hope to achieve design data for our comfortably situated, low cost, ownerbuilt dwelling:
1) At the Hot Climate Physiological Research Unit at Oshodi in Nigeria, Dr. Ladell is conducting valuable research on shading effects.
2) At the graduate school of architecture, Columbia University, a research group was organized in 1951 to study the influence of climate on the Macroform (general planning area) and Microform (architectural details). To date they have made significant progess in the study of solar control and natural air conditioning.
3) In Stockholm, at the Swedish Institute of Technology, Gunnar Pleijel has published extremely interesting material on the use of the “cold sink” as cooling. Cold spots in the north sky have been scientifically determined and temperatures accurately measured. The reflection of the north sky against a wall has an effective sky temperature of 75 degrees — which is 45 degrees lower than the average of about 120 degrees for the south sky. The mirror-like reflection of the north sky explains why livestock will stand in the shade of high-walled buildings in preference to conventional overhead shades. Professor Pleijel’s more recent work involves studies in natural lighting and window protection. Protection, that is, from heat losses from inside the building or from unwanted heat gain from outside.
4) Architect Jacques Couelle, director of the Centre de Recherches des Structures Naturelles, in Paris, has built a number of low cost, naturally air conditioned houses in Morocco. Ground-tempered air is channeled through an inside air space and released at the opposite end of the house.
5) Dr. Ernst Schmidt, professor of thermodynamics at the University of Brunswick, has given considerable study to night-air cooling. His work has special value for use in desert locations where electric current is not available for refrigeration.
6) At Forman Christian College, Labore (now in Pakistan), Professor W. C. Thoburn built several experimental cottages which use a subterranean temperature. In one building, outside air is drawn into the windows of the cellar and then down an air-well to a 14-foot-deep underground tunnel which makes a rectangular circuit of 120 feet of running length. Air is pulled up through a central duct by means of a low power fan and distributed into each room above. This system of “lithosphere building” proved to be especially efficient for summer cooling, as the earth temperature at 15 feet below the ground tends to remain constant throughout the year (76 degrees at Lahore).
7) Wendell Thomas experimented with a simplified version of lithospheric building in two different houses in Celo Community, near Celo, N.C. In one the basement, and in the other the crawl space provided the ground-tempering contact as well as the duct system. Cold air from the exterior house walls circulates into the basement or crawl space through slots between walls and floor. The air is warmed by contact with the lower level and then permitted to rise through a grill located in the center of the house. Both houses, in addition, have solar heating; and the crawl space house is protected from heat and cold by earth banks. In this house the temperature (without overnight-artificial heat) seldom falls, on cold winter mornings, below 60 degrees.
8) Near El Rito, N.M., Peter van Dresser has spent much time and energy developing a low cost solar heating installation. His own solar house engages a complete heat collecting and heat storage system, but in more recent work he is perfecting a partial “sun-tempered” arrangement.
Throughout the humid, the arid, and the temperate regions of the world, these, and many more, independent investigators are making their home design efforts known to all who will but take the trouble to search them out. Though most of their research is still in its experimental stages, enough can be learned by the individual home builder to be of great assistance in planning a more economical and comfortable home.
In effect, this new science of Building Climatology is directed toward the control of climate. The term “Climate Control” is often seen in the literature on this subject. This control is manipulated in two ways; through constructional means and with artificial aids. Cooling by evaporation of water or by fans, and warming by heaters and fireplaces are “artificial” features which are a part of the building, and items of basic equipment which do not call for the consumption of fuel or power, are considered “constructional.” From a practical, economic, or esthetic point of view, I feel that it makes much more sense to develop constructional features for warming or cooling the owner-built home.
Books on Building Climatology
These books are listed in order of importance by the author.
House Beautiful; Climate Control Project, Bulletin Institute of Architects, March, 1950
Physiological Objectives in Hot Weather Housing; Douglas Lee, Housing and Home Finance Agency
Weather and the Building Industry; Building Research Advisory Board, Conference Report No. 1, Washington, D.C., 1950
Application of Climatic Data to House Design; Housing and Home Finance Agency, Washington, D.C., 1954
Symposium on Design for Tropical Living; South African Council for Scientific and Industrial Research, Durban, 1957
Climate and Architecture; J. E. Aronin
The Weather Conditioned House; G. Conklin
Climate and House Design; J. W. Drysdale, Commonwealth Experiment Building Station, Australia, 1945-48