Really “Cool” Roofs Do More Than Keep Out the Rain
When flying in a plane, you recognize that you’re over a city because of the concrete, asphalt and building rooftops below. Those human-made surfaces have a big effect on local weather and the environment, turning urban areas into warmer ‘heat islands’ and causing increased stormwater runoff. Stormwater runs off those surfaces and races to storm drains and streams, carrying pollutants and sediments into our surface waters. A new building feature based on ancient sod roofs is the green or ‘living roof’, which is a specially engineered roof designed to support plants, trees and gardens. Green roofs can help reduce urban overheating and reduce stormwater runoff. According to a study done at Michigan State University, some green roof designs can reduce runoff by up to 80 percent!
Viewer Tip: Look for green roofs on newer commercial and government buildings, such as City Hall in Seattle or the Ballard Public Library. If you are constructing or remodeling a home or business, ask your contractor about the feasibility of installing a green roof. In new construction, the roof can be designed to carry the extra weight of a deep soil layer, water and even shrubs and trees. For remodels, you can use a thin, lightweight system with just a few inches of soil to support small plants. Make sure to consult your local building department when planning your project.
This information is provided by the Port Townsend Marine Science Center. Learn more: www.ptmsc.org.
Seasons: Spring, Summer, Fall, Winter
(Sources: VanWoert et al. (2005) Journal of Environmental Quality 34(3):1036-1044.
Seattle Public Utilities Resource Venture: Stormwater http://www.resourceventure.org/green-your-business/green-building/natural-stormwater-management#consider-a-green-roof. US EPA Dept. of Water and the Low Impact Development (LID) Center: Low Impact Development (LID) Urban Design Tools Website: Green Roofs at http://www.lid-stormwater.net/greenroofs_home.htm.)
