Green Roofing Taking off - Germany Sets the Standard

NEW YORK (AP) -- An architectural organization has unveiled a new "green" roof for its own building to showcase a trend toward environmentally-friendly technology.

The leafy rooftop of the American Society of Landscape Architects building in downtown Washington is a model of the techniques used increasingly to cool temperatures, filter air, and lessen the burden on sewers by absorbing rainwater.

Visitors are surrounded on three sides by a variety of plants, and the aluminum grating that serves as a walkway is suspended over more vegetation.

Green roofs, first championed in Germany, have grown in popularity around the world, and experts predict more growth as the practice sprouts as far away as China. In North America, green roof space grew 70 percent last year.

"What you're going to see is a meteoric rise in this industry because it takes serious issues like storm water and offers multiple solutions," said Steven Peck, president of Green Roofs for Healthy Cities, a non-profit industry association.

Germany, which helped launch the trend beginning in the 1950s, now has 50 square miles (32,000 square acres) of green roof space and adds an additional five square miles (13 square kilometers) per year, estimates Christian Werthmann, an assistant professor of landscape architecture at Harvard's Graduate School of Design.

Green roofs began to spread when some German cities encouraged building owners to substitute ballast and tar rooftops with vegetation. Werthmann estimates 40 German municipalities require green roofs in at least some cases.