CONTACT: Julia Robey Christian, PIO: 202.741.0842 desk | 202.450.7878 cell | [email protected]
WASHINGTON, DC, May 8, 2015—The Washington, DC Metropolitan Region has been recognized for the second year in a row as number one in North America for green roof installations. In its 2014 Annual Green Roof Industry Survey, Green Roofs for Healthy Cities (GRHC) reports that the DC area installed over 1.2 million square feet of green roofs (or vegetated roofs) in 2014. The metropolitan region of Toronto, Ontario ranked number two, with 775,216 square feet installed, followed by Philadelphia and Chicago.
“I’m proud that the District of Columbia continues to lead the nation in installing green roofs,” said Tommy Wells, Director of the District Department of the Environment (DDOE). “The District is recognized as one of the most sustainable cities in the world, and our business and development community’s continued commitment to reducing the city’s carbon footprint plays an integral role in how the District is working to address climate change. With the recent adoption of rigorous stormwater regulations, an innovative Stormwater Retention Credit Trading program, and other progressive green infrastructure policies, our nation’s capital is using public-private investment to accelerate change with a focus on restoring and protecting our natural resources. I look forward to continued collaboration with environmental stakeholders and friendly competition with other cities and regions of the country.”
DDOE offers an incentive to commercial, institutional, residential, and other building owners who voluntarily install green roofs. Through DDOE’s RiverSmart Rooftops program, owners may receive base funding of $10 per square foot to retrofit their properties with green roofs and up to $15 per square foot for properties located within priority watersheds. New construction is also eligible, provided the vegetated roof is not used to meet regulatory stormwater requirements.
Green roofs retain rainfall, which reduces combined sewer overflows and prevents stormwater runoff from carrying pollution and sediment to streams and other waterways. Vegetation dramatically reduces the temperature of the roof and surrounding area through evapotranspiration, a natural process where rainfall both evaporates from the surface of the roof and returns to the atmosphere through the roots and leaves of plants (transpiration). This process reduces the urban heat island effect and helps cool the District as the vegetated roofs absorb sunlight that would otherwise be converted into heat energy.
The American Society of Landscape Architects (ASLA) studied the performance of the green roof on its headquarters in downtown Washington, DC and determined that it has been as much as 32°F cooler than the conventional black roofs on neighboring buildings. In addition, the areas of the ASLA green roof with thicker growth and greater coverage were found to be even cooler. Finally, according to GRHC, green roofs help reduce the distribution of dust and particulate matter in urban areas. This can, in turn, reduce greenhouse gas emissions and assist cities as they adapt to climate change.
Aside from the many environmental benefits offered by green roofs, these systems also carry with them significant economic rewards. First, due to their demonstrated ability to insulate building interiors, green roofs greatly reduce heating and cooling costs. A study of the Target Center in Minneapolis, MN showed dramatic energy savings.
Vegetation also increases the lifespan of a roof by shielding it from the elements, especially ultraviolet radiation that degrades the materials in traditional roofs. Finally, green roofs have been shown to increase property value; building owners are able to charge higher rents in return for the aesthetic benefit provided by landscaped space.