The Future of Green Roofs




A few weeks ago, our office visited a NYC Parks Department Five Borough Administrative Building on Randall’s Island to see an ongoing experiment in green roof installations. Admittedly, we did not know what to expect and thought at best we might see a few planters with sedum and flowers.

We were pleasantly surprised and even a bit overwhelmed by what we encountered. When we arrived, John Robilotti, a Senior Project Manager for the Parks Department with a background in horticulture, gave us a Power Point presentation on the green roof installations and described how he started the program a few years ago with a minimal budget, donated materials, and a lot of free labor. In four years, he has created a green roof testing lab that should be visited by anyone in the metropolitan area who has an interest in designing or constructing a green roof.

When we went up to the roof, we saw approximately 25 examples of green roofs spread out over 29,000 SF, ranging from the traditional sedum installation in trays to more intensive roofs where wildflowers and tall grasses were growing. In a large area over the garage, Mr. Robilotti and his crew installed a new roof system from Germany, “XeriFlor,” which requires about 1½” of soil. There was a plant wall, container systems for fruits and vegetables, and testing areas where the same plants were being grown in different soil types to determine which soil mixture required the least maintenance and water. More information about the project can be found here:

Mr. Robilotti has accomplished the unthinkable: with very little money, but the support of his peers, he has built what is probably the only green roof in the country that actively tests different systems side-by-side on city-owned property. As architects and green roof designers struggle to convince their clients of the advantages of green roofs (decreasing a roof’s ambient temperature adjacent to condenser intakes, thus significantly reducing the amount of energy required to cool outdoor air; reclaiming real estate space; creating habitat for wildlife; doubling or tripling a roof’s life; and managing storm water runoff), he has already done most of the legwork for us by testing soil types, researching appropriate plant species, simplifying installations, etc.

As interest and awareness in green roofs continues to grow, it is worth stepping back and understanding their potential impact in our city. According to Laurie Kerr, senior policy advisor at the mayor’s Office of Long-Term Planning and Sustainability, there is approximately 1.5 billion square feet of roof area in the five boroughs. This represents 20% of total city land area that is largely underutilized. One of the entrants for the Gowanus by Design inaugural design competition proposed a series of linked private/public green roofs that would create a secondary pedestrian experience through and above buildings. The competition’s winning team proposed peeling away the hard surfaces to reclaim real estate beneath broad swaths of green space. Perhaps is it time we stop looking at our cities as simple three-zoned areas (land, buildings, and sky) and start considering them as complex organisms with active interstitial structures that can support technologies, such as green roofs, without sacrificing the increased densities that 21st century urban centers will require.

Posted by David Briggs