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
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 Star® 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.