ConEd and Columbia Study Shows Green Roofs Retain More Water Than Expected

by , 05/19/11
filed under: Energy,Green Space,News

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Water is one of the most fantastic and essential resource this plant has to offer and New York City is beginning to better understand water’s urban benefits, especially in the fight to clean-up its waterways. Back in 2008, ConEdison, NYC’s electric company, teamed up with Columbia University’s Climate Center at the Earth Institute to construct a green roof atop ConEd’s Long Island City building in Queens in order to study the benefits that green roofs offer. In addition to reinforcing the well-known fact that green roofs help reduce the heat island effect, the research team discovered that the green roof retained 22 percent more water than originally suspected and cost very little to maintain.

ConEd’s green roof retained some 30 percent of rainwater, helping to significantly reduce the combined sewer overflow problem that plagues New York City waterways. Skeptics of green roofs have stood by the argument that green roofs have no real cost-benefit that could persuade enough people to jump on board. However, this new research proves just the opposite. The researchers found that based on the cost of building and maintaining a green roof, it costs as little as 2 cents a year to capture each gallon of water. Plus, the fact that green roofs capture 22 percent more water than previously thought, proves that green roofs can help reduce combined sewage overflow (CSO) more effectively than conventional practices.

The benefits from ConEd’s 21,000 plants also prove to be more effective than rain barrels, which eventually and gradually released water to treatment facilities. Because the plants absorb rainwater, they release water vapor back into the atmosphere, a natural process of the water cycle, which keeps unnecessary water out of facility treatment plants altogether. Plus, increased plant life in urban areas can also capture pollutants and filter city air, which fits nicely into the master plan that is PlaNYC 2030.

A vast majority of Manhattan is covered by building footprints, and if 1 billion square feet of those roof tops were transformed into green roofs, it could help prevent more than 10 billion gallons of water from flowing to treatment plants which would reduce the cost of water and waste treatment. Although this was the company’s first green roof planted for education and research, ConEd has turned many of the its facilities’ roofs into green and blue roofs under its “cool roofs” program.

This research is some of the first done in the U.S., and it is sure to help New York City become a sustainable city of the future. On top of that, it strengthens the support for alternative water management programs such as the Gowanus Canal Sponge Park and various workshops that teach private residents and businesses how to green their own roofs.

Via Marketwire and TriplePundit

Image and Video © ConEd