ASPHALT ANTIDOTE
“Living” Roofs Absorb Runoff

by Jennifer Sparger

While we are well aware of the aesthetic and ecological value of growing plants and trees on lawns and indoors, most
people don't realize that growing plants on a rooftop can drastically reduce storm-water pollution.

Living roofs, also known as green roofs, consist of multiple layers that promote plant growth, provide proper water
drainage and filtration, and prevent roots from growing into a building—all while absorbing up to 100 percent of
rainfall. Living roofs have been covering European industrial and office buildings for more than a quarter century. But
Chris Taylor, director of marketing and operations for Building Logics in Virginia Beach, Va., says such roofs have
been slow in coming to the United States.

“We've been doing this now for three years, and it's a hot topic with architects and designers,” Taylor says. “I think
you will find more and more of it in the future, but the practicality of it needs to be demonstrated.”

Living roofs cost about 30 percent more than a conventional roof, but the roofs partly pay for themselves in storm-
water runoff prevention, among other benefits. Runoff is dirty water, full of sediment, drippings from automobiles, and
litter. It infiltrates rivers and streams and can be blamed for half of the water pollution in the United States, according
to the U.S. Environmental Protection Agency.

Local government officials in Arlington County, Va., hope to show the benefits of the green roof with Courthouse
Plaza in Arlington. The retrofit roof covers the original tar and gravel roof making it pleasant to gaze on from
surrounding buildings, says Joan Kelsch, an environmental planner for Arlington County. “The roof also makes the
building cooler, thus saving energy on air conditioning. ... The soil and plants protect the waterproofing layers so they
last up to two to three times longer than a standard roof, which saves significant amounts of money in the long run,”
says Kelsch. And, the roof mitigates the impact of storm-water runoff.

The structure of a green roof is not significantly more expensive than a conventional roof, says Taylor of Building
Logics. “The additional layer of a soil medium and the planting on top of that is where the extra dollars come from,”
says Taylor.

The cost of living roofs may decline as they gain acceptance and competition increases, says Roger Schickedantz,
an associate partner with the Charlottesville, Va., firm, William McDonough + Partners. A green roof adds about $11
to $13 per square foot to the cost of a conventional roof, he says. The Charlottesville firm designed the world's
largest living roof on the Ford Motor Company's renovated Rouge assembly plant (see “Dollars in the Dirt” in the
Winter 2004 issue of Region Focus).

Before he began specializing in green roof plants, Ed Snodgrass, owner of Emory Knoll farms in northern Maryland,
discovered the value of drought-tolerant perennials while trying to make his farm more sustainable. With a
background in environmental education, Snodgrass realized that plant cover would “become an issue with the
explosion of the suburbs around Washington, Baltimore, Richmond, and Philly.”

As farmland turns to asphalt and rooftops, green roofs could play a big role in storm-water prevention. Roofs
represent 15 percent to 30 percent of the total land area in major cities. That's a lot of potential for green space.
But rooftop renewal won't happen quickly without incentives. “Having watched the slow pace at which solar panels are
being accepted in the United States, I wouldn't expect green roofs to fall into place any faster,” Schickedantz notes.
“Both these technologies seem to flourish only where there are incentives or regulations in place.”