New York Fertilizes Green Roofs

Green roofs are a go, thanks to New York State.

More specifically, a bill signed by Governor David Paterson on August 5 promises to spur green roof development atop New York City co-ops and condos by providing a substantial tax abatement worth a quarter to a third of the typical installation cost. Under the legislation, buildings meeting guidelines will be able to take an abatement of $4.50 per square foot of green roof, up to a maximum of $100,000 for the entire job.

Until now, green roofs have generally been high-end showcases, such as the one at Battery Park City’s Riverhouse, or they have been projects financed by such environmentally conscious non-profits as Sustainable South Bronx (at 890 Garrison Avenue in the Bronx). A third variety has been the project of municipal government, such as the Bronx Hall of Justice. Yet another flavor comes from the business owner with environmental credentials, like Stuart Suna of Silvercup Studios, who installed a 35,000 square foot green roof in Long Island City three years ago. But can green roofs catch on in the hard-nosed world inhabited by co-op and condo boards?

Martin Meltzer thinks they can. Spurred by the prospect of the tax abatement, Meltzer, a retired physician and the president of the co-op at 395 Riverside Drive, and his seven-member board have given the go-ahead to a committee to obtain cost estimates for a green roof. It would sit atop their 116-unit Manhattan cooperative at 112th Street and cover roughly 6,500 square feet. According to Dr. Paul S. Mankiewicz, the executive director of the Gaia Institute and a board member of the New York City Soil and Water Conservation District, that’s enough to make an ecological impact. “Each 10,000 square-foot green roof can capture between 6,000 and 12,000 gallons of water in each storm event,” he says. “This is rainfall that will never enter the combined sewer [system]. At the same time, the evaporation of this rainfall will produce enough heat removal to noticeably cool ten acres of the city.”

What else can a green roof do? Advocates point to the following:
A green roof reduces smog
It provides better building energy efficiency by reducing cooling and heating loads, saving fuel and electricity
It improves air quality, by virtue of the increased plantings
It produces local food and habitat for birds, insects and plants

An analysis of the effectiveness of the green roof atop the Silvercup building by Earth Pledge, a Manhattan-based nonprofit in the area of sustainable technology, showed a significant effect in mitigating building temperatures as well as “between 50 and 70 percent storm water capture,” says Leslie Hoffman, Earth Pledge’s executive director.

As environmentally savvy New Yorkers know, there are two types of green roof. The first, the “intensive green roof,” or roof garden, generally features trees and other large plants and requires deep soils, intense labor, and high maintenance. Its purpose is usually ornamental, but gardening is also possible. The second, the “extensive green roof,” is characterized by drought-tolerant vegetation grown on a thin layer of growing medium, and it requires little maintenance and usually no irrigation.

Studies done in Germany in the 1980s – Berlin has an extensive network of green roofs and the German government requires green roofs in new buildings over a certain size – showed that grasses will dominate a green roof when the soil is between 10 to 20 centimeters in depth. If the soil layer is less than 10 centimeters (2.5 inches), the genus Sedum and mosses are most successful. Sedum, a hardy succulent with water-storing leaves and five-petalled blossoms, is the extensive green roof plant of choice, and it’s what you’ll see in most urban installations. Also common are native grasses and another succulent, semper vivus, says Hoffman.

Rob Crauderueff, the policy director for Sustainable South Bronx, says a three-inch layer of gravelly soil topped by plants weighs 30 pounds or less per square foot when dry, information an engineer will have to consider when estimating how much a green roof will weigh. Sustainable South Bronx has a green roof installation team that provides estimates and consultations. Hoffman says that shallow green roofs can often be considerably lighter, as little as 15 to 20 pounds per square foot.

Alexandra Woods, a psychoanalyst and co-op owner, chairs the committee investigating a green roof at 395 Riverside Drive. She went with Meltzer to an August 20 presentation about green roofs and stormwater management hosted by the Hafele Showroom in Manhattan and presented by Green Home NYC in association with nonprofit environmental groups. She left inspired and energetic about the project and ready to begin contacting engineering firms for a roof load estimate come September.

“We’re just getting started,” she says. “More and more people have been talking about green roofs in the neighborhood.” She notes that 395 Riverside has just installed a new roof to halt leaks, which makes the decision to consider the green roof “quite gutsy.” Woods believes a green roof will ultimately raise the value of the property. She anticipates future buyers who are environmentally aware will factor the green roof into their decision to buy.

Meltzer sees the co-op’s prospective green roof as a utilitarian addition - something that will help the building conserve energy by furnishing a layer of insulation against cold and a source of evaporative cooling in hot weather. After attending the Green Homes seminar and hearing a presentation by Teresa Crimmens of the Bronx River Alliance, he sees another benefit: the green roof will help retain storm water, easing the burden on Manhattan’s wastewater treatment plants, which are quickly overwhelmed when it rains.

Also consulting Crimmens on the value of a green roof was Diane Fleck, a resident at 200 Riverside Boulevard at 70th Street on the Upper West Side. Fleck would like to see an organic roof garden flourish at the Trump building, which is a condominium. Her husband, Ira, who is on the condo’s five-member board, presented the idea of a roof garden to his colleagues in early September, bringing with him calculations on the value of Albany’s tax abatement. If the full board approves, Fleck is ready to call in a structural engineer. Her interest in the project was spurred by the high cost of organic produce as well as by an article she read over the summer about how green roofs can moderate high urban temperatures. She wants to set up compost bins for much of the building’s kitchen waste and recruit a cadre of volunteers to begin the organic garden if the board approves. Sites for the garden include 3,000 square foot roof esplanades on the third and fifth floors, as well as the building’s roof, 48 stories above Riverside Park.

Larry Levine, an attorney with the Natural Resources Defense Council, who took questions at the August 20 Green Homes event, believes the tax abatement for green roofs would be available as of January 1, 2009 (the date applications can be filed) with qualifying projects eligible to incur costs as of the date the bill was signed, which was August 5, 2008. A deadline of March 15, 2009, for the submission of documents applies to projects spanning each current fiscal year, which ends every June 30. Requirements for a successful application include a certification by an architect, engineer, or other qualified professional that the roof meets the law’s requirements, which include a commitment by the co-op or condo corporation to maintain the green roof for at least three years and allow periodic inspections. The New York City Department of Finance and the Department of Buildings will probably both have roles in administering the tax abatement. The abatement is a one-time benefit and can only be taken over one year.

Levine adds that the city may be considering modifying residential water bills to reflect not only the cost of providing water but of treating stormwater runoff from paved surfaces. If a building installs a green roof, he says, the city considers a corresponding reduction in water charges.

Hoffman, of Earth Pledge, reports “many calls” about green roofs from co-op and condo board members, asking for presentations and advice. “They’re interested to know, can my building support a green roof, and, what will it cost?” she says. Hoffman advises them that “your first step is to get a structural engineer to tell you what your potential roof load is.” She says most buildings will be able to take “at least a thin profile green roof, that weighs 15 to 20 pounds per square foot.” She says that the Albany tax abatement has made a big difference: “If you start with a $20 per square foot price,” she explains, “and you can get $4.50 a square foot back, that’s a substantial benefit, in many cases, enough to make the return on the building’s investment make sense.”

In addition to the other benefits, Hoffman also cites the aesthetic value of a green roof, which “makes what is otherwise wasted space into a living, pleasant, garden area. Most of the green roofs we have had anything to do with have a place for people as well, like a little terrace. So you get that aesthetic benefit, whether you’re sitting out on the green roof or viewing it through a window.”