Data Confirm Green Roof Water Benefits

Monitoring results from the first two years of operation of a 1,600-square foot "green roof" at the University of Central Florida found that it can retain 80 percent of the average annual stormwater volume from its surface, thereby reducing flooding and water pollution.

Additionally, using stormwater to irrigate the green roof reduces the need for potable water for irrigation, one of the biggest uses of potable water in the state, the Florida Department of Environmental Protection (DEP) recently announced.

"Investing in new 'green' technologies to reduce stormwater pollution, conserve energy and protect our rivers, lakes and springs will further water quality protection and provide clean water to meet future water supply needs," said DEP Secretary Michael W. Sole. "This project is a great and leading example of how to adopt environmentally sustainable practices that not only protect natural resources but also help reduce the potential for some of the harmful effects of climate change."

Green roofs have been used for approximately 50 years in Europe, where benefits such as stormwater management, energy conservation, improved air quality and improved health have been recognized.

In January 2004, DEP contracted with the University of Central Florida (UCF) Stormwater Management Academy to construct and monitor the green roof as part of a multi-year research project to study low-impact best management practices. The green roof was built on a new addition to the university's student union building. Researchers monitored the new green roof extension and a section of the traditional roof to compare stormwater and energy characteristics and determine how the roof affects energy consumption and stormwater runoff.

Energy monitoring identified that the green roof is much more energy efficient than even an Energy StarĀ® conventional roof. The results show as the green roof matures and the other roof ages, the potential energy saving in the summer months jumps from 18.8 percent to 43.3 percent.

The UCF green roof project was funded by a $350,000 grant through the DEP water as part of its mission to develop new best management practices to reduce stormwater pollution. An additional $37,000 from DEP's Florida Energy Office helped assess the energy savings associated with green roofs as part of a larger project focused on energy efficiency at the UCF campus.

Green roofs are an innovative stormwater management solution that can simultaneously improve the energy performance of buildings, air quality and the urban ecology without taking up additional land, officials said. In addition, life-cycle costs are reduced because the roof lasts longer than the standard 10 years to 20 years --some lasting as long as 50 years or more.

Green roofs use drainage systems that allow a layer of vegetation to grow on flat or sloping roofs and a cistern to store stormwater. The stormwater filtrate is used to irrigate the green roof. The design reduces energy transfer through a roof, decreases stormwater pollutants and lessens stormwater volume by naturally evaporating the runoff through the plants, officials said.

For more information about the UCF Green Roof Project, go to http://www.stormwater.ucf.edu.

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