Green Roof Tour Recap: Greening NYC Rooftops

Green roofs have been around for ages—think sod roof houses in rural Europe—but the technology is relatively new to New York. Pushing the leading edge is the NYC Parks’ Five Bor­­ough Green Roof Garden Lab, which studies green roofs from a sustainability perspective. Led by Parks Assistant Commissioner Artie Rollins since 2006, the 29,000-square-foot lab displays various green roof growth techniques and technologies to encourage uptake by public and private sectors. Last week, Rollins (pictured above) took Urban Green Council members on an exclusive tour of the Five Borough Green Roof Garden Lab to demonstrate the different technologies and discuss the rapid growth of the industry (pun intended). Rollins stressed the importance of what his lab is trying to accomplish by pointing out all that these roofs can do for the city.

Green roofs provide a number of passive benefits, or ecosystem services, to the building dwellers and to urban populations at large. First, they naturally detain rainwater, providing a vital service to the region’s waterways. New York City still relies on combined sewer overflows (CSOs) that send excess sewer water into the city’s bays, rivers and canals during rainstorms. This means that storms with relatively small amounts of rainfall can send untreated sewage directly into our waterways. Green roofs combat this by soaking up rainwater as it falls and either transpiring it back into the air or slowly letting it drain away once the storm has passed.

Green roofs also combat the urban heat island effect. Cities throughout the world experience higher temperatures than their surrounding suburban and rural areas. All the black asphalt and tar roofs blanketing New York City absorb the sun’s heat and increase the ambient air temperature by as much as 10 to 15 degrees. This results in increased energy consumption, air pollution and greenhouse gas emissions, and puts communities at greater risk for heat-related illnesses and death. Green roofs combat this by transpiring water into the air, and reducing the surrounding air temperature from around 150°F to 90°F on the hottest days. Rollins pointed out that the Five Borough Lab was looking to downsize their current A/C units, as their green roofs make the larger units unnecessary.

Upon reaching the lab’s roof, the first thing that stood out was the sheer variety of green roof tech on display. There were low-cost, low-maintenance extensive systems with six inches or less of growing medium that could be installed in as little as a couple of hours by only a few technicians. Rollins also showed us intensive green roof systems, that use growing material with a depth of eight inches or more that can hold a wider variety of plant life—even a dwarf pine tree! The diversity of systems being tested by the Five Borough team are designed to showcase that there’s a solution for all roof shapes, sizes and budgets.Beyond the wide range of technology and plant life on display at the Five Borough Lab, members were impressed with how quickly Rollins and his team have influenced the industry in New York City. In 2006, the largest green roof in NYC was in Long Island City, Queens. When the facility had to make upgrades to their building and needed to remove their green roof, Rollins and his team relocated it. What was once the largest system in the city is now just a small corner of the Five Borough Lab. And the Parks facility is only the fifth largest green roof in NYC. The Javits Center boasts the largest vegetated roof in the city, and second largest in North America. It was not lost on Urban Green members how important the Five Borough team has been in fostering these gains. But as Rollins was quick to point out, “NYC agencies only own around 15 percent of the roofs in New York. We need you in the private sector to help us bring green roofs to the other 85 percent.”

Visit Flickr to see additional photos from this event.