Raising the Bar on Green Roof Design
How does ASLA’s unconventional green roof design perform?
By Theodore Eisenman
In keeping with a rising tide of green roof design and construction across the country, the American Society of Landscape Architects
(ASLA) has recently completed an innovative example of vegetated rooftop at its
national headquarters in Washington, D.C. Unlike many conventional green roofs
that clothe a building’s existing profile with the requisite structure, soil,
and plants, Michael Van Valkenburgh Associates took the green roof standard a
step farther by redefining the three-dimensional character of the space.
A defining feature of ASLA’s new rooftop is two symmetrical waves that rise from a central walkway. Finished with galvanized steel decking
and a palette of grasses, succulents, and perennials, these geometric berms
speak to the idiosyncrasy of green roofs: a naturalistic landscape typology
re-created several stories in the air. Unlike many green roofs, however, this
one does not conceal its architectonic nature.
“Many people might be surprised to know that Le Corbusier was exploring green roofs as early as the 1930s,” says project manager
Christopher Counts, ASLA, of the famed modernist architect. “We drew
inspiration from his work and philosophy and made a fairly intentional effort
to not hide the industrial character of the roof.”
At first glance, plants share equal billing with wood and
steel. But in an innovative gesture that sets this project apart from others,
the metal grating that dominates the walking surface floats three inches above
low-growing plants. As these sedums fill in, they are expected to peek through
the grating, creating a novel interplay between contrasting materials. Over
time, one can even envision the ground plane reflecting the movement pattern
and desire lines of users.
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