Green Roofs. If buildings sprang up suddenly out of the ground like mushrooms, their rooftops would be covered with a layer of soil and plants. That’s not how humans build, of course. Instead we scrape away the earth, erect the structure itself, and cap it with a rainproof, presumably forgettable, roof. It’s tempting to say that the roofscape of every city on this planet is a man-made desert, except that a desert is a living habitat. The truth is harsher. The urban roofscape is a little like hell—a lifeless place of bituminous surfaces, violent temperature contrasts, bitter winds, and an antipathy to water. But step out through a hatch onto the roof of the Vancouver Public Library at Library Square—nine stories above downtown—and you’ll find yourself in a prairie, not an asphalt wasteland. Sinuous bands of fescues stream across the roof, planted not in flats or containers but into a special mix of soil on the roof. Living roofs aren’t new.
Technology is only partly the reason. Green Roofs | Heat Island Effect. A green roof, or rooftop garden, is a vegetative layer grown on a rooftop. Green roofs provide shade and remove heat from the air through evapotranspiration, reducing temperatures of the roof surface and the surrounding air. On hot summer days, the surface temperature of a green roof can be cooler than the air temperature, whereas the surface of a conventional rooftop can be up to 90°F (50°C) warmer.1 Green roofs can be installed on a wide range of buildings, from industrial facilities to private residences. They can be as simple as a 2-inch covering of hardy groundcover or as complex as a fully accessible park complete with trees.
Green roofs are becoming popular in the United States, with roughly 8.5 million square feet installed or in progress as of June 2008.2 Benefits and Costs In addition to mitigating urban heat islands, the benefits of green roofs include: This apartment building in Portland, Oregon, is among the 6 acres (24,300 m2) of green roofs in the city, as of 2007. 1. . 3. How Green Is Facebook's Massive Green Roof? - Rebecca Greenfield. Greenroofs.com: The Resource Portal for Green Roofs. GRHC.