Con Ed’s 10,000-square-foot green roof, which was installed in July and is the first at one of its buildings, is more advanced than most projects. The company spent $200,000 to install 1,350 trays filled with 21,000 plants, including 15 varieties of sedum. The plants, which were cultivated at a nursery in Connecticut, sit in a mixture of volcanic rock, sandstone and other light stone capable of absorbing water.
Green Roofs Offer More Than Color for the Skyline
The bottoms of the trays look like egg cartons; they allow a small amount of water to pool beneath the plants. The trays can easily be moved to provide access to the roof if there are leaks that have to be plugged. Con Ed chose sedum not only because it can absorb rainwater quickly, but also because it is not indigenous to New York, making it unlikely to attract potential pests. The plants also require very little maintenance.
Con Ed has teamed up with Columbia University’s Center for Climate Systems Research to evaluate the benefits, using rooftop sensors to measure the temperature, wind and water runoff. Con Edison said it hoped to use the findings to encourage customers to install green roofs themselves.
David Westman, the resource conservation coordinator at Con Edison, said, “It’s not only the right thing to do, but it can make economic sense.”