Courtsey Rafael Viñoly Architects
Storm water runoff is considered one of the greatest ecological hazards facing urban areas. A dearth of open land and vegetation in cities means there are fewer places for rainwater to be absorbed; consequently, it drains into sewers, which then overflow, polluting waterways. Green roofs have been heralded as one infrastructure solution by large municipalities like New York City, which recently passed legislation requiring the development of a citywide Sustainable Storm Water Management Plan. The “urban heat island effect” is a phenomenon in which the temperature in urban areas like New York City can be 1 to 10 degrees warmer than in surrounding suburban or rural areas. William Riley, a construction manager for Pratt Center for Community Development, explains that this occurs because the predominately flat roofs of city buildings absorb and radiate heat back into the environment. Heat from the rooftops as well as waste heat from air conditioners and industry activity gets trapped in urban canyons, contributing to record-high temperatures that put undue strain on urban residents and energy systems used to keep them cool. Vegetative coverings have been shown to reduce the ambient temperature of roofs. According to the Environmental Protection Agency, on hot summer days, the surface temperature of a vegetated rooftop can be cooler than the air temperature, whereas the surface of a traditional rooftop can be up to 90°F warmer.
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A Problem and a Solution So with a multitude of advantages, why doesn’t
s New York’s architects and engineers search for ways to reduce energy usage and pollution, green roofs are becoming increasingly popular. The constructions address environmental maladies facing urban areas while, in many cases, offering educational opportunities for New York City’s schoolchildren. As a result, green roofs are making the city cooler and less polluted and contributing to a higher level of environmental consciousness among the nation’s youth. The rise in popularity of vegetative, or green, roofs is due, in part, to the growing awareness of environmental hazards faced in urban areas—in particular, the rise in temperature in these areas due to the “urban heat island effect” and the pollution caused by storm water runoff. Pratt itself will use a green roof on its proposed LEED Gold building at 524 Myrtle Avenue to both insulate the roof and to capture storm water.
every city building have a green roof? Riley, who has been involved in energy conservation projects since the early 1970s and has built and tested the effectiveness of green roofs as part of his work with the Pratt Center for Community Development says, “The additional square foot cost associated with green roofs make this option less attractive to building owners, who instead choose more cost-effective
Green roofs are contributing to a higher level of environmental consciouness among the nation’s youth. alternatives as roofing insulation and light/heat reflective paints. Green roofs won’t truly flourish, Riley predicts, until municipal governments offer tax rebates or other incentives to encourage vegetative roof projects. 29