Landscapers See Opportunity in the Sky
27 Dec, 2007 By: Brian Albright LDB SolutionsLandscape designers spend a lot of time looking down—understandable, since their livelihoods are inextricably linked to the soil. But Kurt Horvath, owner of Intrinsic Landscaping in Glenview, IL, has his head in the clouds these days. Horvath is one of a growing number of landscapers specializing in the design and construction of green roofs, those eco-friendly islands of greenery that dot the formerly drab roofscapes of cities around the world.
According to Green Roofs for Healthy Cities (GRHC), the North American industry association, green roof installations in 2006 were up more than 25%, representing more than 3 million square feet. For intensive green roofs, which incorporate larger plants, the growth rate was 110% during the same period.
Horvath's company, which includes a nursery and two landscaping divisions, was contracted to install its first green roof back in 2000. More than 100 installations later, he has built an entirely new business focused on these rooftop projects, as well as a subsidiary that manufacturers and distributes green roof components.
"Those installations have been a mix of anything and everything," Horvath says. "If you can put it on a roof, we're there."
Layered Styrofoam acts as a terrace for the soil on top of the roof. Photo courtesy of ASLA.
There is expected to be significant opportunity in the green roof market in the coming years as more and more businesses and homeowners look for ways to reduce their impact on the environment, but experienced designers and architects warn newcomers to do their homework before leaping into a project. Unlike traditional installations, or even simple rooftop gardens, green roofs require a wide variety of expertise, ranging from horticulture to structural engineering.
"There's a to more to green roofs that meets the eye," says Steven Peck, founder and president of Green Roofs for Healthy Cities. "There are a lot of ways to mess up a green roof. It's a living system. It's very important to follow the lessons we've already learned to make sure it doesn't leak, that the plants survive, and that you get the maximum benefit for your climate."
There are two basic types of green roofs: extensive (which include shallower soil depths and smaller plants), and intensive (with larger plants and deeper soil). While designs vary, green roofs typically include a waterproofing membrane and some sort of lightweight growing material. As an example, the green roof installed at 1425 K Street in Washington, D.C., includes a waterproof membrane/root barrier, a two-inch layer of polystyrene insulation, a layer of geo-textile filter fabric, and an inch-thick drainage mat, topped off with three inches (33,000 pounds) of engineered soil held in place with a loosely-woven jute mat.
The roofs also have to be properly contained on all sides, either using the existing features of the roof or specially designed barriers, a structural element sometimes overlooked by inexperienced architects.
For more information on this growing trend, including examples of green roofs and planting tips, see the January/February edition of Livescapes.
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