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Either or both of two motive forces may be employed for natural ventilation one is convection and the other is wind. Air flows through a building because of the tendency of air to migrate from a higher-pressure area to a lower-pressure one. In convective ventilation, differences in pressure are created by the difference in density between warmer air and cooler air, which causes warm air to rise (11.6,11.7). In wind-powered ventilation, the air flows from a higher-pressure area in one side of a...

The Outdoor Environment

Earth is unique among the planets of our solar system in offering all the basic necessities of life. But human life is far from easy on most parts of the globe. A planet-sized atmospheric engine, fueled by radiation from the sun and cooled by the radiation of heat back into the emptiness of space, moves air, moisture, and thermal energy across its surface in restless patterns that create an outdoor environment of varied and often extreme conditions. The sun is the single most important factor...

Controlling Air Movement

Clean, oxygen-rich air for breathing is the most pressing environmental requirement for human life. Continuously moving air is also a primary requirement for thermal comfort, to convect away excess body heat and evaporate perspiration. Although the air in a rural outdoor environment contains such natural pollutants as odors, bacteria, pollens, spores, molds, and dust, we usually perceive it as being pure, and all but the most allergic persons find it optimum for breathing. Air movement in the...

Prologue Sustainable

Buildings represent a huge investment, not only of money and time, but also of the world's resources. In constructing and occupying buildings, we consume vast quantities of materials and generate a major portion of the world's environmental pollution. According to the Worldwatch Institute, buildings consume more than 40 percent of the energy utilized in the world each year and, in so doing, release into the atmosphere one-third of the carbon dioxide and two-fifths of the compounds that cause...

Providing Water

French Drain Roof

Buildings and settlements require an adequate supply of clean water for drinking, cooking, washing, industrial processes, and agriculture. This requires a system that has three basic components a source of water a means to purify the water, if necessary and a way to distribute the water to points of use inside buildings. In primitive circumstances people dip water into small containers from ponds, streams, or rivers. If the water is free of harmful substances, they simply drink it on the spot...

Controlling tke Radiation o f Heat

Not Familiar Environment

One essential role of a building in providing thermal comfort is controlling the flow of thermal radiation to and from the human body. Sometimes a building must protect the body from an excessive influx of radiant heat from the sun or from sun-warmed objects. At other times, protection is needed to prevent an excessive radiation of heat from the body to a cold outdoor environment. Exchanges of radiation also take place continually between the body and the surrounding interior surfaces of the...

Keeping a Building Alive and Growing

Even before a building is completed, Nature begins to destroy it systematically. Gravity, wind, and seismic movements constantly test the stability of the structure. The ultraviolet wavelengths of sunlight fade organic building materials and break down their molecules. Rainwater dissolves carbon dioxide and sulfur dioxide from the atmosphere to form weak carbonic and sulfuric acids that eat away at stone and encourage the oxidation of metals. Where two adjacent metals of dissimilar electrolytic...