It is Karen McGowan’s job to keep plants growing inside malls, hotels and office buildings around the Capital Region. Now, she’s getting ready to start greening up the rooftops.
McGowan has handled “interior plant-scaping” at Faddgeon’s Nursery Inc. in Latham for years, so “it seems like a natural evolution” for her and the firm to get into the burgeoning “green roof” movement.
Composed of living plants and earth, green roofs are gradually showing up in the United States, years after first being used in Europe and Asia. A green roof stays cooler during the summer than a traditional roof, and reduces a building’s energy consumption. A thirsty roof also soaks up rain to reduce the amount of water running into storm sewers.
In March, McGowan, a 15-year employee at Faddegon’s, was certified as a green-roof designer and installer by Green Roofs for Healthy Cities, a Toronto-based trade group with about 5,000 members.
“Some of the oldest roofs in Europe are now about 40 years old and still going strong,” McGowan said. “The market in the United States is just starting to develop.”
In the Capital Region, green roofs are in place at the Barton Mines headquarters in Glens Falls and at Creo, a restaurant at Stuyvesant Plaza in Guilderland. The Adirondack Wild Center in Tupper Lake also has one, as does The Golden Arrow Lakeside Resort in Lake Placid.
With more than 600 such roofs in place, Chicago was the first U.S. city to aggressively promote the technology, and even uses it atop City Hall. The roof kept the surface temperature about 50 degrees cooler during a hot summer afternoon, when compared to a traditional black tar roof. Chicago officials estimated that trimmed annual energy bills by more than $3,000.
Just about any building can have a green roof, as long as a couple of important conditions are met: the roof has to be strong enough to support the weight and it cannot be too steep. At up to six inches thick, a green roof can weigh 40 pounds a square foot when wet, McGowan said.
“You need to have a structural engineer determine what kind of load a roof can support,” she said. And the slope of the roof can be no more than 40 degrees to prevent the material from slipping off.
Green roofs can be built from scratch with plants started in place, or they can be “pregrown” elsewhere and installed in prefabricated modules that snap together.
Both types require multiple layers beneath, to keep roots and water from penetrating the roof.
Plants are usually hardy alpine types that can handle the harsh exposed conditions. Maintenance consists of occasional trimming with a weed whacker, and spraying with a solution to ward off pests and fungus. (McGowan recommends a mix of water and hydrogen peroxide.) A healthy roof will reseed itself, so as plants age and die, new plants fill in, she said.
At $25 a square foot, installation of a green roof can initially be more expensive than a traditional roof. But over time, the green roof can save money.
Researchers at the University of Michigan found that a 21,000-square-foot green roof would cost about $464,000 to install, compared to $335,000 for a traditional roof. But the green roof would save about $200,000 in reduced energy costs and better stormwater management over its lifetime.
