Saturday, May 6, 2006
"Green roofs" are like successful politicians -- lofty, tenacious and good to their constituents.
Too bad Washington's new stadium complex was conceived without any.
As a smart design phenomenon, green roofs are flourishing, and the benefits are numerous: A rooftop sprouting the thinnest layer of vegetation can cool the island of heat a city radiates in summer. Through photosynthesis, plants purify smoggy air. More important, in the case of a ballpark at the edge of the Anacostia River, succulents on structures like parking garages could absorb and cleanse rainwater, diminishing the runoff that threatens waterways all the way to the Chesapeake Bay.
But the selling points remain easy to ignore.
Take the Nationals' stadium, a megaproject and role model for development along an urban waterfront with fabulous potential. Despite a decree from the D.C. Council to incorporate the best environmental practices, the ballpark's architects, HOK Sport and Devrouax & Purnell, failed to specify even one symbolic square inch of green roof. (The playing field doesn't count; unlike the plantings on a green roof, grass requires massive amounts of fertilizers and water to flourish.) The environmental package was so lacking that last week, D.C. Council member Jack Evans (D-Ward 2) convened a meeting of designers, D.C. Sports and Entertainment Commission representatives and clean-water advocates to demand better solutions.
The commission contends that the existing design is more environmentally friendly than any major league ballpark and that funding is exhausted thanks to the council's cap on spending.
Evans puts the cost of environmental enhancements at a mere $5 million to $10 million.
Ironically, there's a model of green-roof design two blocks from the stadium site. The twin headquarters buildings of the Department of Transportation, under construction on M Street SE, will be topped with 68,000 square feet of sturdy sedum. The federal project, controlled by JBG Cos., is among the biggest green-roof projects underway on the East Coast. A $100,000 grant from the Chesapeake Bay Foundation helped defray a small portion of the extra costs of waterproofing and planting.
"This was not easy," says Paul Elias, managing director of construction for JBG. "You've just got to make it happen."
Last week, the American Society of Landscape Architects inaugurated a green roof atop its headquarters at 636 I St. NW. The project, which cost nearly $1 million, also received a stipend from the bay foundation. The 3,300-square-foot expanse is little more than a potted plant compared with the Transportation Department's roof. But as a visitor-friendly educational setting, its impact could be huge.
There is public access to a terrace designed by Michael Van Valkenburgh, a National Design Award winner and designer of the pedestrian stretch of Pennsylvania Avenue in front of the White House. While the Transportation Department's roof is inaccessible, this one has been designed for enjoyment. Two miniature hills block glare and the cacophony of air-conditioning units on neighboring roofs. Cactus rises on one ridge, while perennial grasses flutter on the other. A trellis will provide shade once vines take hold.
Aesthetics alone should help push the discussion of green roofs from commercially viable to enjoyable. But the association takes the educational value of the project seriously. It will install equipment to monitor roof temperatures and runoff.