green roof
n. A roof that is covered with plants, particularly one in which special membranes and other layers serve to protect the rooftop and hold the plants and soil in place. Also: green rooftop.
green-roof adj.

Example Citations:
Green roofs serve three major benefits to the city, said David Reynolds, first deputy commissioner for Chicago's Department of Environment. They help manage storm water by soaking up rain that would otherwise go into the sewer system. They absorb carbon from the air, and they reduce the urban heat island effect.
—Pamela Dittmer McKuen, "Installing green roofs can benefit the environment—and budgets," Chicago Tribune, May 21, 2004

Green-roof technology refers to a complex system of root-repellant and waterproof membranes, lightweight growing media, drainage layers and plants which rest directly on the rooftops. It does not include potted plants. The benefits include savings on energy for heating and cooling, decreased roof maintenance, sound insulation and aesthetic appeal. These benefits are greatest in the summer and most cost-effective in buildings with high air-conditioning costs.

Although considered a new concept in Canada, green roofs have been used extensively in Europe for more than a decade. More than 10 percent of flat roofs in Germany contain green-roof infrastructure.
—"Green roofs Qualify for Government of Canada Energy Efficiency Funding," Canada Newswire, May 12, 2004

Earliest Citation:
Living on the edge of a marshland with plants sprouting from his roof, Maarten Regenboog could well be considered a guinea pig in yet another Dutch social experiment. Instead he sees himself as a happy resident of a community of the future. ...

Truly 'Green' Roof

The sod roof took some getting used to, he admits, but helps keep the top floor warm in winter and cool under the summer sun. It looks kind of hairy, with the sod bearing short, thick-leaf plants.
—Marlise Simons, "Earth-Friendly Dutch Homes Use Sod and Science," The New York Times, March 7, 1994

Notes:
A green roof is also called a living roof (1993) or an eco-roof (1993).

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