The development of "green" buildings that regenerate degraded urban environments is essential to building healthy, sustainable communities in the 21st century. According to the U.S. Environmental Protection Agency and Lawrence Berkeley National Laboratories, Berkeley, Calif., rooftops represent 15 percent to 30 percent of the total land area in major cities. As such, they present a tremendous opportunity for positive change as a key component of green building and sustainable roof system design.
There are two basic types of green roof systems: extensive and intensive. Extensive green roof systems range from 1 inch to 5 inches (25 mm to 127 mm) in soil depth, typically consist of mosses and herbs, and are built primarily for their environmental and economic benefits rather than public access. Intensive green roof systems require at least 1 foot (0.3 m) of soil depth, elaborate irrigation and drainage systems, and maintenance. Typically designed to be publicly accessible, intensive green roof applications feature trees and shrubs and often resemble city parks.
The multiple paybacks of green roof systems are far-reaching and involve a mix of public and private benefits, including the following:
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