![]() New buildings with a total floor area of more than 21,527 square feet will, depending on their size, have to cover from 20 to 60 percent of their roofs with vegetation. This year Toronto became the first city in the Western Hemisphere to mandate green roofs. Liptan figures that if half the roofs in the city were green, Portland would reduce its storm water burden by some 3 billion gallons, a quarter of the rainfall that hits the city’s roofs annually. If we trap it on the roofs, we don’t have to build bigger pipes to carry it or cisterns to store it for treatment.” We were trying to find a way to reduce the burden on the city. “It was a cost/benefit evaluation,” says Liptan. In Portland, Oregon, the city provides incentive grants of $5 per square foot for what they call “eco-roofs.” There’s no limit on the size of the roof, but Tom Liptan, a storm water specialist with the city, says that most of the grants have so far gone to homeowners or to buildings in the commercial district. In Europe, Stuttgart and Copenhagen have begun to mandate green roofs on most new construction. added 190,000 square feet in 2009 and has set a goal of 20 percent green roof coverage by 2020. city, last year added 600,000 square feet of green roofs and has some 600 projects that will bring its total to 7 million square feet. ![]() Although initially more expensive than standard asphalt or shingle roofs, green roofs offer major environmental and economic advantages, from slashing storm water runoff and energy costs, to cooling overheated cities and cleaning their air.Ĭhicago, which now has more green roofs than any other U.S. The sprouting of a large, living roof in midtown Manhattan is a sign that this universally lauded green practice, which has spread rapidly across Europe, is now gaining a serious foothold in the U.S. Postal Service estimates that the plants’ ability to cool the roof in summer and insulate it in winter will reduce the building’s energy costs by $30,000 a year. Since the roof has been installed, the building’s storm water runoff into the New York municipal water system has been reduced by as much as 75 percent in summer and 40 percent in winter. The plants’ size and modest requirements, however, belie their substantial biological capacities and environmental benefits. ![]() ![]() The vegetation is a densely planted assemblage of some 25 hardy, low-growing species that have thrived in their few inches of planting material. The 2.5-acre park on the Morgan Processing and Distribution facility is the biggest green roof in New York. ![]()
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