Yenra : Environment : Green Roofs : Green roofs cool for summer, environmentalist says.

Green roofs composed of special infrastructure to support soil and plants are better than conventional roofs at insulating homes in winter and keeping them cool in summer, according to preliminary study results at University of Toronto.

"We found that, on the whole, the green roof was better at protecting the delicate roof membrane - one of the most sensitive parts of a roof's infrastructure - from extreme temperatures than a conventional roof," says Professor Brad Bass of the Institute for Environmental Studies and a researcher for Environment Canada's Adaptation and Impacts Research Group.

Bass and his colleagues at the National Research Council constructed an experimental roof - half being a traditional flat roof and the other half, with a six-inch layer of soil and wildflowers on top of a special drainage layer and a root-repellent, waterproof membrane. The researchers found that the green roof was effective at maintaining a cooler summertime roof surface temperature, reduced storm water run-off and kept summer temperatures inside the structure lower due to the cooling effect of the vegetation.

"The green roof acts as insulation," Bass explains. "The vegetation on the roof also provides shade and returns moisture back to the atmosphere, preventing a significant amount of solar energy from being absorbed by the roof." Funding for the study was provided by the Climate Change Action Fund with contributions from private roofing firms and Environment Canada.