Designing with Green Roofs: Maximizing Sustainability and Stormwater Management

New urban roof top gardens lower energy costs and increase environmental benefits
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Advertorial course provided by American Hydrotech, Inc.
Celeste Allen Novak, AIA, LEED AP

Case Studies

Some garden roofs are sloped or even curved, such as the building for Gap, Inc. in San Bruno, California, designed by William McDonough + Partners, of Charlottesville, Virginia. "How many buildings do you know that have made oxygen lately?" William McDonough, FAIA, often asks architects. Intensive garden roofs are designed for a maximum slope of 51-to-300 millimeters (two- to twelve-inches).

Extensive garden roofs can have steeper slopes, and some green roofs have been installed up to a 45 degree slope. Design for roof slopes requires analysis of the climate, wind direction, and sun angles. The amount of snow, and rain patterns, will affect the type of plant on each side of the roof slope, depending upon the roof orientation.

Bruce Eisenberg, AIA, Director of Architecture for the New York City Department of Parks and Recreation, in Flushing, New York, is completing design in 2005 for a new green roof at the Marine Park Senior Center, in Brooklyn, with estimated completion in 2007. As the first sustainable green building designed in-house by city employees, the structure will be equipped with photovoltaic solar panels, a geothermal system, and an extensive green roof, which blends into the environment. It will reduce the heat island effect of the urban location and reduce stormwater runoff, keeping much of it on-site, while removing pollutants, thereby reducing the impact on the City's overloaded waste system. "The green roof, with an unusual round form, and rooftop photovoltaics, responds to the environment," says Eisenberg. The design team is striving for compliance with the U.S. Green Building Council's (USGBC) rating system, Leadership in Energy and Environmental Design (LEED), and a silver rating.

In 2005, Eisenberg noted, Mayor Michael Bloomberg signed legislation mandating that by 2007, 50 percent of all New York City agencies with capital projects exceeding two million dollars will be required to comply with the USGBC's LEED program, with the goal of achieving silver ratings. This law will significantly increase interest and demand for green roofs with New York City.

Architects Pappageorge Haymes Ltd., designed the rooftop at the Domain Lofts at ePort, in Chicago, Illinois. The site was an abandoned Montgomery Ward & Company Catalog House, with a footprint too wide for rehabilitation as housing. The designers chose to remove a large swathe of interior construction building new walls and a new roof exposed to the elements. This is an example of how architects can design a new roofscape for tenants where the view to the garden is better than the view on the street.

Gardens improve the quality of life, and add quantifiable real estate value to projects and the built environment. Green roofs are a good business decision for rooftops of new mixed-use housing complexes, and hotels with rooms facing rooftop vents and gravel landscapes.

Research demonstrates that human health is improved by exposure to nature, fresh air and growing plants. In hospital and healthcare environments, views to natural landscapes enhance healing, and gardens have traditionally served as sources of respite and inspiration. The Japanese create Zen gardens for meditation.


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Originally published in Architectural Record.