From the U.S. Food and Drug Administration building in Washington DC to Heinz Corporate head quarters in Pittsburg, an increasing number of buildings are swapping shingles for sedums. The movement is called green roofing, but far from an industrial paint job, it evolves around technology that's ecologically-sound -- and proving so useful that cities like Portland, Oregon, Chicago, Boston, Seattle, and the entire state of Maryland are eagerly exploiting the potential of this once forgotten façade.
"This technology offers us an opportunity to significantly improve not only the way our buildings operate, but to utilize wasted spaces -- there are millions of square miles," says Steven Peck, founder and president of Green Roofs for Healthy Cities, an organization established to increase awareness of green roof benefits. GRHC also hopes to advance the market in North America. "The roofing industry is just at the beginning of a process of transformation. Nothing can match the range of social, economic and environmental benefits green roofs provide."
As the name implies, green roofs are roofs made of plants. They're comprised of a waterproof membrane followed by a root barrier, a drainage layer, and finally the growing medium and a variety of plants, grasses, sedums, cactus or shrubs -- hence, the green. The technology, of course, isn't entirely new. For millennia, the natives of Scandinavia and Iceland, particularly barren environments with limited building materials, used sod on their roofs as insulation; in Tanzania, mud huts with grass roofs are common; and closer to home, many early settlers used sod to insulate their walls and prairie grass to cover their roofs.
Green Roofs Today
In more recent years, Germany spearheaded the modern movement back to grassy rooftops, but this time with an urban twist. During the 1970s, the densely-populated country began installing green roofs to prevent storm water from surging into its aging sewer systems, and the industry has since boomed, experiencing rapid and sustained growth. Today, roughly 14 percent of the country's total roofs are greened, the industry continues to grow 10 percent per year and some German cities actually levy a "rain tax" on non-greened, asphalt rooftops.
More:
http://www.alternet.org/envirohealth/48530/
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