Heating, Cooling, Lighting: Design Methods for Architects - Hardcover

Über die Autorin bzw. den Autor

Norbert Lechner is Professor of Architecture in the Department of Building Science at Auburn University and a registered architect in the state of Alabama. His articles have appeared in Architectural Lighting and Solar Today.

Auszug. © Genehmigter Nachdruck. Alle Rechte vorbehalten.

HEATING, COOLING, AND LIGHTING AS FORM-GIVERS IN ARCHITECTURE "Two essential qualities of architecture [commodity and delight], handed down from Vitruvius, can be attained more fully when they are seen as continuous, rather than separated, virtues. . . . In general, however, this creative melding of qualities [commodity and delight] is most likely to occur when the architect is not preoccupied either with form-making or with problem-solving, but can view the experience of the building as an integrated whole--. . ."

John Morris Dixon 1.1 INTRODUCTION Until about 100 years ago, the heating, cooling, and lighting of buildings was the domain of architects. Thermal comfort and lighting were achieved with the design of the building and a few appliances. Heating was achieved by a compact design and a fireplace or stove, cooling by opening windows to the wind and shading them from the sun, and lighting by windows, oil lamps, and candles. By the 1960s, the situation had changed dramatically. It had become widely accepted that the heating, cooling, and lighting of buildings were accomplished mainly by mechanical equipment as designed by engineers. Our consciousness has been raised as a result of the energy crisis of 1973. It is now recognized that the heating, cooling, and lighting of buildings are best accomplished by both the mechanical equipment and the design of the building itself. Some examples of vernacular and regional architecture will show how architectural design can contribute to the heating, cooling, and lighting of buildings. 1.2 VERNACULAR AND REGIONAL ARCHITECTURE One of the main reasons for regional differences in architecture is the response to climate. If we look at buildings in hot and humid climates, in hot and dry climates, and in cold climates, we find they are quite different from one another. In hot and dry climates, one usually finds massive walls used for their time-lag effect. Since the sun is very intense, small windows will adequately light the interiors. The windows are also small because during the daytime the hot outdoor air makes ventilation largely undesirable. The exterior surface colors are usually very light to minimize the absorption of solar radiation. Interior surfaces are also light to help diffuse the sunlight entering through the small windows (Fig. 1.2a). Since there is usually little rain, roofs can be flat and, consequently, are available as additional living and sleeping areas during summer nights. Outdoor areas cool quickly after the sun sets because of the rapid radiation to the clear night sky. Thus, roofs are more comfortable than the interiors, which are still quite warm from the daytime heat stored in the massive construction. Even community planning responds to climate. In hot and dry climates, buildings are often closely clustered for the shade they offer one another and the public spaces between them. In hot and humid climates, we find a very different kind of building. Although temperatures are lower, the high humidity creates great discomfort. The main relief comes from moving air across the skin to increase the rate of evaporative cooling. Although the water vapor in the air weakens the sun, direct solar radiation is still very undesirable. The typical antebellum house (see Fig. 1.2b) responds to the humid climate by its use of many large windows, large overhangs, shutters, light-colored walls, and high ceilings. The large windows maximize ventilation, while the overhangs and shutters protect from both solar radiation and rain. The light-colored walls minimize heat gain. Since in humid climates nighttime temperatures are not much lower than daytime temperatures, massive construction is not an advantage. Buildings are, therefore, usually made of lightweight wood construction. High ceilings permit larger windows and permit the air to stratify. As a result, people inhabit the lower and cooler air layers. Vertical ventilation through roof monitors or high windows not only increases ventilation but also exhausts the hottest air layers first. For this reason, high gabled roofs without ceilings are popular in many parts of the world that have very humid climates (Fig. 1.2c). Buildings are sited as far apart as possible for maximum access to the cooling breezes. In some of the humid regions of the Middle East, wind scoops are used to further increase the natural ventilation through the building (Fig. 1.2d). In mild but very overcast climates, like the Pacific Northwest, buildings open up to capture all the daylight possible. In this kind of climate, the use of "bay" windows is quite common (Fig. 1.2e). And finally, in a predominantly cold climate we see a very different kind of architecture again. In such a climate, the emphasis is on heat retention. Buildings, like the local animals, tend to be very compact, to minimize the surface-area-to-volume ratio. Windows are few because they are weak points in the thermal envelope. Since the thermal resistance of the walls is very important, wood rather than stone is usually used (Fig. 1.2f). Because hot air rises, ceilings are kept very low (often below 7 feet). Trees and landforms are used to protect against the cold winter winds. In spite of the desire for views and daylight, windows are often sacrificed for the overpowering need to conserve heat.