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Natural air circulation is a preoccupation of green architecture. With the widespread adoption of air conditioning after World War II, the typical office building was constructed to be more airtight than a mummy's tomb. Now designers are rediscovering principles of ventilation and air circulation familiar to builders of the 19th century. The Rocky Mountain Institute took part in an environmental upgrade of the White House and the vintage Executive Office Building nine years ago. "We discovered that the old office building was already designed with a natural ventilation system--a fairly brilliant one," says William Browning, the institute's senior consultant for green development. Parts of that system, which once linked chimneys and other air passages, are now back in operation.
Not everything green is rosy. To provide sunlight that reduces reliance on electrical lighting, environmentally conscious designers tend to favor open-plan workplaces over offices with doors that close. That can be good for nature, less good for quiet and privacy. And big suburban residential developers are not piling in yet. Reduced long-term energy costs, for instance, are not an important incentive to builders who plan to sell off the homes they build right away.
Some green architecture is literally green. Dwellings that nestle directly into the landscape like caves, with carpets of earth and grass rolling over them as roofing, were among the first and most thoroughgoing examples of green architecture in the 1970s. Buildings like those take their inspiration from such time-honored examples as Bronze Age settlements that were dug into the earth. But they operate on principles that can be adapted to modern midtown high-rises. For the past year, Chicago's City Hall, a 1911 Classical Revival building, has been topped by a "green roof"--a 20,000-sq.-ft. garden that was planted as a climate-control mechanism. Built from a blend of compost, mulch and spongelike materials that hold water more effectively than regular soil, the low-maintenance garden of 20,000 plantings is intended to reduce City Hall's air-conditioning and heating costs by as much as $6,000 each year.
In summer the garden helps keep the building cool by shielding it under a layer of moist material. In winter it insulates against cold. In both seasons, it reduces the storm-water runoff that occasionally overflows the Chicago sewers leading to Lake Michigan. Though the garden has yellowed a bit this summer, it still provides its cost-cutting benefits. Not incidentally, it also provides a habitat for birds, butterflies and grasshoppers. But not yet for people--the garden is closed to the public. Sometimes nature needs to work in peace.