Green roofs are living roofs.
- Angela Cesere
The “green” is a layer of vegetation planted on top of a building, incorporated into the roof structure. The resulting roof-plant concoction has been hailed as a significant step toward an environmentally friendly and economically sound approach to building. European countries, especially Germany, have been taking advantage of this technology for more than a century, and more recently, American cities like Chicago and Boston are catching on.
In Michigan, the Ford Rouge auto manufacturing plant is home to the largest green roof in the world. Built in 2003 over what used to be a 100-mile-long railroad system, 10.4 acres of green lie atop the manufacturing facility.
The plant, called sedum, is selected because it can withstand harsh environments and needs little maintenance. Blanketing the factory, it does wonders for power conservation at the plant.
“What we have with the sedum grass roof is both heating and cooling, an insulating factor which is a huge reduction in energy costs,” said Christian Overland, vice president of venue operations at the Henry Ford Museum. “So it’s not just the idea of a grass roof, you’re reducing your power needs.”
Not only does the roof reduce energy costs, it also plays a large role in maintaining the natural environment around the plant. Before the Rouge plant was built, the Ford company drained seven million gallons of water a day from the Rouge River for manufacturing needs – more water than is consumed in a day in Cincinnati, Detroit and Washington, D.C. combined.
With the green roof, graywater – rainwater that has been filtered through the green roof system (see lower-left corner photos) – is used directly in the manufacturing process, lessening the impact on the river and the local environment.
Aside from reducing damage to the Rouge River, the green roof also replaces green space that was destroyed with the construction of the building.
Over the years, a variety of wildlife has made a home of the Rouge plant’s rooftop. Last spring, a Canadian goose built a nest among the 12 different types of sedum and moss on the green roof.
Joel Perkovich and Brian Chilcott, both graduate students studying landscape architecture at the University, are conducting research on 20 varieties of native Michigan plants to see if they can be used on green roofs in the area. Their goal is to diversify plants on green roofs, Perkovich said.
“If you’re able to use a lot of native plants, you’re increasing the biodiversity of plants that are growing on green roofs,” he said. “There’s more value to local wildlife.”
Simulated green roof boxes were built in the spring and testing began in June. At the end of three growing seasons, the plants that have survived in the boxes are guaranteed to survive on top of an average business or residence.
Ann Arbor local Bob Grese an associate professor of natural resources at the University, is practicing what he teaches on the roof of his own garage. Grese made the garage roof green two years ago when he and his wife decided to rebuild the entire structure. The couple’s bedroom window now overlooks wildflowers and strawberries rather than the dull rooftop of before. Aside from the roof’s new aesthetics, the filtered water runoff from the roof system irrigates some of the surrounding plants in his prairie front lawn. Both lawn and roof are living proof of Grese’s commitment to increasing green spaces and improving local ecology.
As green roof technology is refined and its benefits advertised, it’s picking up steam in homes and businesses. In Vancouver, the Fairmount Waterfront Hotel is already saving an estimated $30,000 a year just by growing herbs, vegetables and flowers on the roof.
Saving green never sounded so good.
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