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In the late 1960s, many people in North America turned their attention to environmental problems, and new steel-and-glassskyscrapers were widely criticized. Ecologists pointed out that a clusterof tall buildings in a city often overburdens public transportation andparking lot capacities. Skyscrapersare also lavish consumers, and wasters, of electric power. In one recent year,the addition of 17 million square feet of skyscraper office space in NewYork City raised the peak daily demand for electricity by 120, 000kilowatts -- enough to supply the entire city of Albany, New York, for a day. Glass-walledskyscrapers can be especially wasteful. The heat loss through a wallof half-inch plate glass is more than ten times thatthrough a typical masonry wall filled with insulation board. Tolessen the strain on heating and air-conditioning equipment, builders of skyscrapers have begun to use double-glazedpanels of glass, and reflective glasses coated with silver or gold mirror films that reduce glare as well as heat gain. However, mirror-walled skyscrapers raise thetemperature of the surrounding air and affect neighboring buildings. Skyscrapersput a severe strain on a citys sanitation facilities, too. If fully occupied,the two World Trade Center towers in New York City would alone generate2.25 million gallons of raw sewage each year -- as much as a city the sizeof Stanford, Connecticut, which has a population of more than 109, 000. | 
