The Marriott Hotel in Victoria, British Columbia, Canada, has a green roof above the entrance to the underground parking. (Photo courtesy of Pacifi c Northwest Regional Architecture)
Green roofs transform wasted space into a thriving natural environment.
These wooden roof panels are not wood at all. They are made of durable metal made to look like beautiful weathered wood with cool coatings. These panels are prepainted then formed into roofi ng panels, giving them a fl awless, long-lasting fi nish. (Photo courtesy of National Coil Coating Association)
roof. Installers must ensure that no punctures occur, because tiny holes are diffi cult to fi nd and repair. Routine monitoring of a green roof’s underlay-
ment is no different than maintaining any compara- ble roofi ng system. When leaks are detected under green roofs, a procedure exists for cutting out and removing a section of green roof and reinstalling it after repair.
Acceptance issues Unlike the growing cool roof industry, the benefi ts of green roof technologies are poorly understood and the market remains immature in the United States. However, in Europe, green roofs have be- come very well established. This is the direct result of government legislative and fi nancial support at both the state and municipal level. This support has led to a multimillion dollar market for green roof products and services in Germany, France, Austria and Switzerland. In Germany, it is estimated that 14 percent of all buildings are covered with vegeta-
tion, a number that is increasing as the German green roof industry continues to grow 10 to 15 percent per year. Will green roofs ever catch on in the United
States like they have in Europe? According to Michi- gan State University’s Department of Horticulture’s Green Roof Research Program, several barriers to widespread green roof acceptance exist in North America. These include a lack of awareness regard- ing green roofs, potentially higher installation costs, limited quantifi able data pertaining to the benefi ts they provide, no technical information on how to build them, and a lack of government incentives or tax breaks. But these problems are not insurmountable and are being addressed. Meanwhile, in Chicago, codes offering incen-
tives are available to builders who put green roofs on their buildings. The Chicago City Hall green roof is one of the fi rst and most well-known examples of green roofs in the United States. It was planted as an experiment to determine the effects a green roof
A cool roof is measured by two properties: solar refl ectance and thermal emittance. (Image courtesy of Cool Roofi ng Rating Council)
would have on the microclimate of a roof. Accord- ing to the Chicago Department of Environment, on hot days, temperatures atop it are typically 25 to 80 degrees Fahrenheit cooler than an adjacent county offi ce building with a black top roof.
The best of both When installed correctly, cool roofs and green roofs have excellent insulating properties. But, “cool roofs and green roofs are different technologies used for different applications,” says Clark. “Both have their own environmental and energy effi ciency benefi ts. Cool roofs and green roofs are complementary tech- nologies, and can be combined by using cool pavers on a green roof patio space.” Ferraro agrees, saying both cool roofs and
green roofs can increase a building’s energy effi - ciency and recommends adopting a “whole building envelope approach” when trying to reduce building energy consumption and achieve maximum ef- fi ciency results.