How Do Green Roofs Work? [Scientific American Magazine]

Cities worldwide are promoting environmentally “green” roofs to mitigate several urban problems. Ground cover, shrubs and other flora planted across a building’s roof can reduce storm water runoff, easing the burden on local sewers and water treatment systems. And the vegetation can keep the roof cooler in summer, lowering interior air-conditioning costs and therefore peak demand on area power plants.

Green roofs have been blossoming in Europe for more than a decade, and Tokyo now requires that at least 20 percent of any new roof on medium and large buildings be cultivated. Chicago is the U.S. leader. Most installations are made on newly constructed buildings, but retrofits are rising.

[More]