Con Edison Media Relations
COLUMBIA STUDY FINDS CON EDISON’S ‘COOL ROOFS’ SAVE ENERGY, HELP THE ENVIRONMENT
Green or White Roofs Both Have Benefits
NEW YORK —Green and white roofs atop a Con Edison training and conference center in Long Island City, Queens, help prevent energy losses and provide important environmental benefits compared to traditional dark roofs, according to researchers from Columbia University (www.coned.com/coolroofstudy).
The “green roof,” consisting of 21,000 plants, keeps heat in the building during the winter, reducing the need for heating, and keeps heat out during the summer, reducing the need for air conditioning. The energy saving benefits of the white roof occur mainly in the summer, when the roof absorbs less heat than a dark roof, cutting down on air conditioning needs.
The green and white roofs perform equally well in preventing a phenomenon scientists call “heat island effect,” according to the study, led by Stuart Gaffin, a research scientist at Columbia’s Center for Climate Systems Research. Conventional dark roofs absorb sunlight during the day and radiate heat back into the atmosphere at night, contributing to warmer urban temperatures.
As part of its effort to combat global warming and encourage energy efficiency, Con Edison has installed white roofs on its Manhattan headquarters and other buildings. The company has installed nearly 250,000 square feet of white roofing and has plans for at least another 220,000 square feet by the end of 2010.
To establish a green roof, Con Edison began growing plants in August 2008 on a quarter-acre section of The Learning Center roof adjacent to the two other experimental roof sections, one white and one dark.
In its quest to learn about energy efficiency and eco-friendly strategies, Con Edison commissioned a study by Columbia scientists to measure temperatures and other data on the green, white and dark sections. The goal was to determine the environmental and energy-consumption performance of each type of roof.
“This study by one of the world’s top universities confirms the benefits of our ‘cool roofs’ program,’ said Saddie Smith, Con Edison’s vice president of Facilities. “We strongly encourage building owners to consider ‘cool roofs,’ whether white or green. They save energy and they’re good for the environment.”
“Ultimately the goal of this effort is to provide the best science so we can inform the various policy choices and cost-benefit estimates for energy conservation,” Gaffin said.
Smith said building owners need to carefully consider the costs and benefits of each type of cool roof. While green roofs are more energy efficient and carry benefits such as water runoff control and noise reduction, a green roof is more expensive than a white roof.
The green roof on The Learning Center reduces summer heat gains by up to 84 percent and winter heat losses by up to 37 percent, compared to a black roof. The white roof reduces summer heat gains by up to 67 percent. These figures represent only the reduced amount of heat flowing through the roof, not a building’s energy consumption. Many factors – such as windows and insulation – also affect a building’s total energy usage.
In the next phase of the research, Gaffin will be joined by Columbia University colleagues, Patricia Culligan, a professor at the Fu Foundation School of Engineering and Applied Science, and Wade McGillis, research scientist at Lamont-Doherty Earth Observatory. They will measure the quantity and quality of the water runoff from the green roof and compare it to the control roofs. Excess storm water runoff in urban areas leads to combined-sewage-overflows that pollute surrounding waterways.
Con Edison is a subsidiary of Consolidated Edison, Inc. [NYSE: ED], one of the nation’s largest investor-owned energy companies, with approximately $14 billion in annual revenues and $34 billion in assets. The utility provides electric, gas, and steam service to more than 3 million customers in New York City and Westchester County, New York.
Con Edison’s commitment to environmental responsibility has been recognized by the global Carbon Disclosure Project (CDP), Innovest Strategic Value Advisors, the U.S. Environmental Protection Agency, the U.S. Department of Energy and other organizations. For additional financial, operations, and customer service information, visit Con Edison’s Web site at www.coned.com.A leading academic and research university, Columbia continually seeks to advance the frontiers of knowledge and to foster a campus community deeply engaged in understanding and addressing the complex global issues of our time. Columbia's extensive public service initiatives, cultural collaborations, and community partnerships help define the University’s underlying values and mission to educate students to be both leading scholars and informed, engaged citizens. Founded in 1754 as King’s College, Columbia University in the City of New York is the fifth oldest institution of higher learning in the United States. For more information, visit www.columbia.edu.