by Bill Millard
Event: Green Walls (Helfand Spotlight Series)
Location: Center for Architecture, 03.24.09
Speakers: Clare Miflin — Associate Principal, Kiss + Cathcart; Marni Horwitz — Principal, Alive Structures; Denise Hoffman-Brandt, ASLA — Associate Professor, City College School of Architecture and Urban Design
Moderator: Susannah Drake, ASLA, Assoc. AIA — dlandstudio, 2009 President, New York Chapter, ASLA
Organizers: AIANY in partnership with the New York Chapter, American Society of Landscape Architects (ASLA)
Sponsors: Alive Structures; Landscape Forms, Inc.; New York City Green Roof and Landscape; Lieb’s Greenhouses Inc.
Green roofs have become a highly visible instrument and symbol of commitment to sustainable design. The same biophilic impulse applied to interior and exterior walls can improve a wide range of environments, but as the green-wall specialists who spoke at the opening of “Work in Progress: Green Walls” at the Center for Architecture emphasized, the practical challenges of working with vegetation are complex. Enthusiasm and good intentions alone won’t create a healthy botanical structure that improves air quality, water management, thermal control, acoustics, and aesthetics; it takes specific expertise and sound judgment about the right species and support systems for a particular space.
Clare Miflin presented a series of success stories including the Solar One environmental learning center at Stuyvesant Cove Park, the vine-covered Riverhouse at the Bronx River Greenway, and the Vertically Integrated Greenhouse, a hydroponic food-production facility proposed as a New York Sun Works demonstration project at the Science Barge on the Hudson. The Bronx project, she recalled, involved the opposite of architects’ customary thinking about hydrology: instead of striving to minimize water requirements, she found in working with the Gaia Institute’s Paul Mankiewicz that a “maximalist” approach to water use was preferable, creating a space with credible resemblance to a temperate rain forest.
Marni Horwitz, a certified green-roof and green-wall installer, recognizes risks as well as benefits. Cautioning that some businesses look to this form of construction for greenwashing purposes, she emphasized that green walls are a young industry with considerable potential to backfire when firms start “experimenting on clients.” One restaurant installed a green wall without proper irrigation; after a striking appearance for the first week or so, the soil dried, the plants died, and diners found bits of soil dropping into their meals. Modular soil-based systems can be dramatically beautiful, she said, but also labor-intensive and costly (up to $150 per square foot); irrigation requires constant attention; simple, seasonal native-species vines such as Virginia Creepers are often the most reliable choices.
The evening’s most visionary discussion, offered by Denise Hoffman-Brandt, ASLA, concerned integrating green walls into broader systemic thinking. Her City-Sink project addresses the function of plants as carbon-sequestering agents, not just ornamentation, in urban space. Retrofitting roadside sound-barrier walls along the Staten Island Expressway and the Brooklyn-Queens Expressway to suspend plants on geotextile fabrics held by rebar cages, creating microclimates and areas sheltered from sun scorch, Brandt’s system converts a component of an otherwise harsh and drab highway environment into an ecological asset.
As NY-ASLA President Susannah Drake, ASLA, Assoc. AIA, pointed out, plants as a design element have a long history, from the Hanging Gardens of Babylon to the ivy of college campuses. Arguments in favor of green walls, as Miflin mentioned during the panel segment, involve measurable cost-benefit ratios as well as intangibles: they reduce asthma and air-conditioning use while providing “increased worker productivity and happiness.” Hoffman-Brandt stressed the scalability of the various benefits relative to initial costs and noted that the more manageable vines, while useful in smaller urban settings, do not maximize biomass for long-term carbon storage as bulkier species do. More complex local ecosystems, including urban fauna — birds, beneficial insects, occasional snakes — are “hard to sell to community boards,” Hoffman-Brandt acknowledged, perhaps touching on a core conflict between philosophies of design: the uncontrollable messiness of nature vs. the urge for predictability and reductionism that shapes many modern spaces. “The thing to take away from these green walls,” she added, “is the kind of language they’re setting up for microclimate and microconditions and diversity” — natural qualities that users and observers of these spaces may need to adjust to.
“No system is going to be 100% perfect, except in theory,” commented Horwitz. The pragmatism and attention to detail in this discussion suggests that the local green-design community has moved well beyond the stage of initial enthusiasm that sees natural elements as a panacea, instead taking a realistic nuts-and-bolts approach to the specifics of leaves and roots.