Gardening on the Side

Architects experiment with moveable green walls

Nancy Rottle didn’t set out to make green walls better—she just wanted to figure out how good they already are. But in the course of creating her own green wall for a study to evaluate these increasingly popular elements of urban sustainability, she encountered a common conundrum. “The big question is, how do you maintain these things?” says Rottle, a landscape architect and director of the Green Futures Research and Design Lab at the University of Washington in Seattle.

“We’ve observed green walls in the Pacific Northwest that have failed, and clearly no one could get to them,” Rottle says. Because of the difficulty of accessing them, green walls may not get watered as often or as thoroughly as necessary, and plants that die go unreplaced.

Rottle’s answer was to design a movable green wall, which was installed on the side of a campus building last summer. Though this wall’s purpose is research, the concept might eventually be applied much more broadly.

To construct the wall, Rottle’s team mounted two ten-by-ten-foot, steel-framed panels to garage door tracks and attached them to the building façade next to second- and third-floor balconies. The researchers can move the panels back and forth by turning a crank, much like putting out an awning. A similar system could also be used to move green-wall panels vertically.

Imagine, for example, stepping onto your apartment balcony and cranking your green-wall panel out to catch some sun, then back in to harvest lettuce and herbs for dinner.

For now, Rottle is using the new green-wall design to experiment with biodiversity. Pockets made of heavy-duty fabric hold about 530 plants belonging to 22 different species—ferns, sedges, sedums, Heuchera. Well over half the plants are Pacific Northwest natives, including salal and Oregon grape. The wall is part of a larger system of experiments in sustainability, including capturing rainwater from the building roof for irrigation and training hops and kiwi vines up another wall to form a green screen.

Rottle and her team plan to track how well the different green-wall species grow and survive, what insects and birds they attract, and whether the plants help cool the building. Little objective information about the ecological benefit of green walls is currently available, but Rottle says that’s exactly what is needed to really scale up. ❧

—Sarah DeWeerdt

Photo ©Leann Andrews

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