Earth Pledge Executive Director Leslie Hoffman Talks About Making the City a Green Place, One Roof at a Time

Manhattan’s first green roof, installed in 1998, sits on top of the 1902 Georgian townhouse at 122 East 38th Street in Murray Hill, the home of Earth Pledge, a New York based nonprofit that promotes green building technologies. Founded by Theodore Kheel to support the 1992 United Nations Earth Summit in Rio, Earth Pledge now sponsors the Greening Gotham program, an initiative to get New York City developers, building owners, and government officials behind green roof installation. Leslie Hoffman, Earth Pledge’s Executive Director, spoke with CityLand about the city’s standing, its policy and turning affordable housing green.

Why Green. Hoffman began as a minimum wage carpenter in Maine, became a general contractor and moved on to design green building projects. She holds a degree in Architecture and Design from Colorado College, has co-authored green technology books and even runs an organic coffee farm. Hoffman explained that green roofs are fundamentally lightweight, engineered systems of insulation, drainage, soil, and vegetation constructed on top of a traditional roof. It’s an “an elegant solution to common urban problems,” Hoffman declared, listing green roofs’ ability to boost insulation, cool buildings, reduce energy use by 10 to 30 percent, lower area air temperature, absorb 80 percent of storm water lessening runoff, and protect the roof from weather cycles and UV rays. Installation adds about $10 per square foot, but Hoffman points out that a green roof can last for 50 years where traditional roofs need replacement after only 15. The Greening Gotham program envisions a network of green roofs stretching across the city’s skyline, which advocates and researchers believe could diminish the “urban heat island effect,” a term used to describe the fact that the city is 3 to 6 degrees hotter on summer days than its surrounding suburbs.

A Greener New York. “New York, like many cities, is starting to realize that it has a serious roll to play in supporting green building projects throughout the city” Hoffman says. In fact, in 2005 the City passed the Green City Building Act, which requires that nonresidential projects costing more than $2 million meet U.S. Green Building Council’s silver LEED standards. In the area of green roofs, however, Hoffman admits that the city has only a handful, lagging behind other urban centers, like Chicago, which boasts over a million square feet. When her organization initially started pushing the idea, Hoffman says there was quite a bit of excitement that narrowed into skepticism as some City officials questioned the actual impact green roofs could have on the city due to New York’s towering skyscrapers. To prove their effectiveness, Earth Pledge moved forward on a number of research projects to prove that green roofs can be useful locally.

Collecting Data. Earth Pledge maintains two data collecting stations on existing green roofs, one on the Silvercup Studios and another on Gratz Industries, the metal fabrication company owned by the family of Landmarks Commissioner Roberta Brandes Gratz, both in Long Island City, Queens. The stations collect data on how green roofs on different buildings types can cool the building, the roof and the air.

Under a contract from the City’s Water Board, Earth Pledge built a modeling tool called the Green Roof Stormwater Model to assess how well a green roof on a specific building will retain storm water. New York, like many cities, uses a combined sewage overflow system that transports sewage together with rainwater. Earth Pledge says that half the time it rains, sewage overflow is released into the City’s waterways. The Stormwater Model investigates the impact green roofs’ stormwater retention properties can have on this problem. Originally developed for lower Manhattan, the model was expanded to cover other areas. Results are not publicly available, but Hoffman works with a wide range of private and public developers to test proposed green roofs and provide data on how well they will retain storm water.

Helping Others. Under Hoffman, Earth Pledge also started the Viridian Project, which provides technical support for affordable housing developers and nonprofits on how to start green roofs. Since its inception, the project has helped build seven green roofs, including two in the South Bronx, one in Harlem, and one in Bedford Stuyvesant, Brooklyn.

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