Donald Sussman, president of the landscaping and design company Town and Gardens, says the most important thing to know about green roofs is that there is not one green roof. “People will call us all the time and say ‘Oh yeah, we want a green roof,’ but it’s really important to understand what they want and need,” he says. Do you want a green roof primarily for environmental reasons? Aesthetic? Recreational? A combination of all three? Adds Jared Markham, project manager for Weston Solutions, which also installs green roofs: “It really does mean something different to every building owner.”
Green roofs are, literally, a growing industry. Nationwide, the number of green roofs increased by 35 percent from 2007 to 2008, according to Green Roofs for Healthy Cities, an industry group. New York came in third nationally behind Chicago and Washington, D.C., for the amount of green roof square footage with 358,986 square feet, the group reports. That’s almost three times as much space as there was in the city in 2007.
There are essentially two kinds of green roofs: extensive and intensive. An extensive green roof is an “environmental” green roof, one that is designed mainly for environmental benefits. Extensive green roofs use a bedding of drought resistant plants to reduce storm water runoff, improve a building’s insulation, and lengthen the life of a roof. An intensive green roof can be anything from a few planters and a walkway to a network of planters and gardens that cover the entire roof.
And while environmentalists are cheering the recent passage of a green roof tax credit for New York City buildings, those cover only extensive green roofs and the application process can be complex and costly, says Sussman. He notes that the tax credit application requires an architect’s certification both before and after the project is completed. To get the credit, buildings also must submit plans for four years worth of roof maintenance. “In most cases, it hasn’t been the financial incentive we were hoping for,” he says.
The tax credit was championed by Mayor Michael Bloomberg and enacted January 1, 2009, and it aims to cover about 25 percent of the cost of the green roof. To meet the standard, 50 percent of the usable roof space must have vegetation and out of that green space, 80 percent must use “drought-resistant plants,” says Rob Crauderueff, policy director for Sustainable South Bronx, the group that helped advocate for the credit and draft the rules.
Crauderueff feels that the property tax credit is worth the effort, arguing that some of the most expensive parts of the application process – say, the roof’s structural analysis – must be done anyway. If a roof meets those qualifications, city property taxes will be reduced for one year by $4.50 per square foot of green roof, up to $100,000.
Under that formula, the Brevoort, a co-op at 11 Fifth Avenue, will get a one-time property tax credit of about $15,000. But that wasn’t the main motivation for the building, says Diane Nardone, its board president.
“This is part of an overall effort the building is making to become as much of a green building as a 1955 building can become,” she says. The co-op is installing two green roofs and is also pursuing cogeneration.
(Another green roof tax credit is also in the works. A proposal sponsored by Councilman David Yassky in February would provide a tax abatement if a building is doing a green roof project under J-51. The credit would be 90 percent of what the city deems the appropriate cost of a project, spread out over 20 years in property tax abatements, says Danny Kanner, spokesman for Yassky.)
The first step for any type of green roof project is a structural analysis to ensure that the roof can support the added weight of the plantings. Sussman says the minimum weight load is 13 pounds per square foot but that he likes to see about 25 pounds per square foot.
Markham says intensive green roofs require that the surface support even more weight, up to 60 pounds per square foot. Where your building stands depends on many factors, but he says those built in the 1920s and 1930s generally have far higher structural capacity than those in the 1950s and 1960s.
The structural analysis can start at about $3,000, says Sussman. If a roof is not up to par, repairs must be made and those (and their costs) will vary.
Next, the roof membrane will almost always have to be updated or replaced, Sussman says. The roof membrane his company recommends costs between $15 and $20 per square foot. With an extensive, the roof’s life can be doubled because it is cooler. A typical roof in summer can hit 180 degrees; a green one is closer to 90.
An extensive green roof includes layers of roof barrier, insulation, drainage, and a growing medium. There are hundreds of varieties of plants, some of them evergreen, that work well in an extensive green roof. There are all colors, shapes, and sizes; some resemble grasses and other flat-leafed plants. In total, Sussman says, the green roof (excluding the membrane) can cost between $20 and $25 a square foot.
At the Brevoort, there is a green roof that was installed in July 2008 on about 90 percent of the 1,400 square feet of the south building. The one on about 90 percent of the 2,300 square feet of the north building will be completed in Spring 2010. The price tag for both will be $57,700. (The underlying membrane, a project that needed to be tackled regardless, will be $422,000.) Nardone says the project will be paid for out of a capital expenditures fund.
The Royal York, a 500-unit cond-op on the Upper East Side, decided on an intensive green roof on the common area between two buildings, giving residents lots of passive recreation space, says Robert Scaglion, board president. The project, plantings, and repairs cost $800,000, paid for by a one-time assessment. “There was the consideration of value and view,” Scaglion says. “We wanted to have a type of green shaded recreational use for the shareholders.”
Board vice president Jay Mitchell admits he was against an intensive green roof project at his building, 222 Park Avenue South. A 50-unit co-op, it put up $200,000 worth of landscaping and spent $1.2 million on the membrane and roof support.
“I’ve sort of come around,” he says. “We did spend a lot of money but we’ll have a beautiful roof that will serve the next generations for years to come.” Mitchell was initially intrigued by the possibility of a tax credit but was disappointed to learn his roof didn’t qualify.
The environmental benefits of an extensive green roof are clear. The Earth Pledge Foundation studied a green roof on the Silvercup Studios building and an industrial building in Queens and found that, compared to a traditional roof, there was a 30 to 70 percent reduction in storm water runoff, says Greg Loosvelt, the group’s chief operating officer. On a shorter building, say two or three stories, a green roof could provide 20 to 30 percent in energy savings, he notes. In a taller structure, only the top floors would see a benefit. But even an intensive green roof is beneficial, says Loosvelt. The growing medium is what holds water to prevent runoff. Evaporating water from soil cools the air. All plants will release oxygen.
Steven Peck, president of Green Roofs for Healthy Cities, an advocacy organization, believes that all green roofs should incorporate residential access. “You want to create a usable space for the occupants of the condo that will provide them with a higher quality of life,” he says. “There are environmental benefits but that’s not the way I would approach it.”
And, if you do pursue an extensive green roof, how can your little green patch in the city’s sea of black roofs make a difference when it comes to environmental benefits? “Have you ever heard the expression ‘a journey of a million miles begins with a single step’? ” Peck says.