April 18, 2005

ASLA Green Roof Begins to Take Shape
Garden will emphasize positive ecological and environmental impacts of green roof technology.

When it comes to green roof construction, there seems to be two schools of thought: In one, the roof garden makes a visual statement using brilliant plants, geometric lines, modern planters, sculptural elements, and even high-concept lighting. In the second, the roof garden sacrifices some of its visual appeal in favor of a more organic approach, eschewing showy plantings and lighting in favor of a garden that highlights the green roof’s positive environmental impact—lowering a building‘s energy costs and helping reduce runoff.

Last week, members of Michael Van Valkenburgh Associates and Conservation Design Forum (CDF) held a charette to discuss the ASLA green roof, formally beginning what Michael Van Valkenburgh, FASLA called “an equal partnership,” to build a high-profile green roof in the middle of downtown Washington, D.C. As the charette wound down, one member of CDF began talking about “changing the perception of weeds”—or what most people consider to be weeds—and it became evident that ASLA will most likely be getting a green roof from the second, ecological school of design. In fact, the charette included a lot of discussion about ecology and low-impact design and a desire not to create a roof that would be a “glossy magazine cover garden.” Rather, the team seemed to reach the conclusion that the roof should allow ecology to take over and cater to plants that can thrive in its inhospitable environment.

“If there’s a kind of moral imperative to a roof garden, it’s an ecological and energy-saving agenda,” Valkenburgh told LAND Online following the charette. “It should be a wonderful garden, but what drives us all to be interested in this are very important cultural things: What we spend our money on and oil and energy dependence. To me, this is what’s exciting about what we talked about today.”

Boards from the ASLA Green Roof Charette Courtesy of Michael Van Valkenburgh Associates

The design team seemed to feel that the high-profile nature of the project, which will likely draw the attention of local and national policy makers as well as design professionals, meant that it is important to create a garden that will showcase the environmental benefits of green roofs. Second, because ASLA will be promoting the use of green roof technology, it’s important that the positive environmental impact of the roof be measurable in some way.

“What’s emerging here is the opportunity for the Society to decide what the mission is for the garden,” Van Valkenburgh said. “We want to address these issues, and do it in a way that we can take some quantitative measure of our accomplishments—change in heat load, how we’re doing with roof runoff, reflectivity. Also, it’s important that what we’re putting up there doesn’t require any environmental surcharge through herbicides, pesticides, fungicides, and nonorganic fertilizers.”

While design elements will come into play in the garden itself, most of the clean, linear elements will be incorporated on the built structures of the roof as the team grapples with what the space presents. Currently, the roof is cluttered with all manner of machinery—vents, ducts, and heating and cooling systems—all of which must be incorporated into the green roof. Van Valkenburgh described viewing the roof in its current state as opening up an empty refrigerator and asking, “How the hell am I going to cook dinner with air?” During the charette, the team decided these elements must be incorporated into the garden through design, at one point noting that some vents could be covered with new facing—perhaps something designed to mimic the chrome grill of a luxury SUV.

"Let’s not apologize for that stuff; let’s not cover that stuff,” Van Valkenburgh said. “Is there a way we can actually make it attractive? Can we change the grills; can we put them in positions where the one thing they do that’s obnoxious—which is make noise—isn’t such a horror?”

With the charette completed and the groundwork for the project laid, the two teams went back to their offices to begin hashing out some of the more practical aspects of the green roof—namely that their ideas fit the budget of their client. They will also examine the physical aspects of the space to ensure that whatever they plan will remain on the ASLA roof, rather than in the third-floor offices of Landscape Architecture magazine. The team will meet up in early May to begin these practical discussions.

Photos from the ASLA Green Roof Charette

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