Topping Off, for the Environment

The sedum plants, now mere seedlings, will grow to cover the roof of an office building in Germantown. (By Preston Keres -- The Washington Post)

Frank Mondell and Jerry Williamson, successful Montgomery County developers, were beaming during a recent rooftop celebration for their new office building in Germantown. Their pride and joy? Small, unremarkable plants that will soon carpet the roof and provide a way to capture and filter rainwater.

Mondell and Williamson aren't your typical tree-huggers. But the tiny forest of sedum plants that they hope takes root alongside the bulky air-conditioning unit and ventilation chimneys will form the basis of the requisite storm water management system. The cost, they said, was relatively minimal. The benefits, they hope, will be immense.

"It was the right thing to do," Mondell said, as he gazed at the paved-over vista that includes a gas station, a couple of shopping centers, and several lanes of traffic along Route 118 and the nearby interstate. The neighborhood, like many parts of northern Montgomery, no longer has many trees or green spaces, which soak up and filter rain and snowmelt before the water flows into local rivers and streams.

Mondell and Williamson, the first to get a "green" roof approved by Montgomery's storm water regulators, are enthusiastic converts to a growing movement of builders, government officials and environmentalists who see such low-tech methods as relatively simple and low-cost ways to improve air and water quality.

They do get something more tangible than just satisfaction from the deal: Montgomery County, whose permitting office asked them to try out the green roof, waived a $75,000 fee for failure to install the more typical storm water management system.

To get builders to use the environmentally friendly systems, many local governments are mulling tax breaks and offering the chance to build more densely. Although data is scarce, the planted roof might, in the long run, save builders money by allowing them to avoid adding holding ponds or underground filtering tanks and to use those spaces more profitably.

The green roof can offer many benefits. The plants -- and the dirt and gravel that hold them -- filter rainwater and some of its pollutants. The plants produce oxygen that can help clean the air. They could help reduce the building's heating and cooling costs, acting as a form of insulation. And they could lessen the "heat island effect," in which buildings warm up so much that they heat the surroundings.

"The side benefits are what we are all excited about," said Richard Gee, a senior staff member in Montgomery's permitting office who worked closely with Mondell and Williamson as they planned the building, just off Interstate 270.

The low-tech green roofs have been embraced in Europe, where rooftop gardens are a tradition. But they have not caught on in the United States.

In the Washington area, about two dozen public and private office buildings have green roofs. Local governments have begun advocating for them as one of several methods to bring the region into compliance with federal clean air and water regulations.

Fairfax County officials are considering incentives for builders who use environmentally sensitive methods. In Arlington County, developers can build more densely if they follow certain precepts of green construction.

In the District, several green roofs are in the works as part of an agreement reached in a lawsuit seeking to resolve a long-standing problem with sewage overflows.