Green Roofs Playing a Greater Role in American Cities

New York, Minneapolis, Los Angeles, Atlanta Among Cities Adopting Stricter Environmental Standards

Green roofs are originally a phenomenon of Europe, but have been playing an increasingly greater role in the US since 1997, according to research published in the June issue of Environmental Health Perspectives (EHP).

According to the study, green roofs are "rooftops that are partially or completely covered with vegetation growing in soil medium over a waterproof membrane." They are important because they boost energy efficiency and reduce ecological harm by controlling stormwater runoff. Green roofs are in the limelight because the EPA, design and development consultancy and advocacy groups, and prominent cities are accelerating the installation of green roof projects and the implementation of green roof policies and practices.

The study says the EPA is currently working on a report detailing national policies and practices relevant to green roof projects and incentives. It has been suggested by consultancy and advocacy groups that the EPA might include green roof incentives as part of the Clean Water Act.

Facts Favoring Green Roofs

Rivers, estuaries, and bays are being harmed by silt, which settles over natural sediment. This causes ecosystem deterioration and water turbidity. Most of the erosion that produces silt occurs because of rainwater and other stormwater runoff, the EHP study said.

Finding a way to decrease runoff will aid in restoring waterway health. The Potomac River, the Anacostia River and the Chesapeake Bay have increased turbidity from an increase of silt from runoff. The study said that Doug Siglin, who directs the Washington, D.C., area Chesapeake Bay Foundation, explains that green roofs reduce runoff by redirecting stormwaters.

A March 2007 report by the non-profit consultancy group RESOLV gave major emphasis watershed health, with sub-watersheds as an additional priority. A watershed is all the tributary and other sources of runoff being fed into a river. Sub-watershed areas are those secondary areas bordering the watershed.