In April 2019 the New York City Council passed The Climate Mobilization Act with the goal of reducing greenhouse gases released from city buildings, which requires the city to implement green roofs, miniature wind turbines or solar panels on newly constructed buildings. In New York City where space is a premium, green roofs must address a host of problems to ensure they are worth the space they use.
The Nature Conservancy, partnered with Green Roof Research Alliance, has created a project to map how many green roofs are in existence and to identify potential sites in the future. According to the Nature Conservancy, there are about 730 buildings that already have green roofs, but this only represents 60 acres of the 40,000 available. This number is less than 0.1% of the city’s 1 million buildings.
There are clear environmental benefits to adopting widespread green roofs. As reported in Dwell, the National Research Council of Canada found that if a building adopts a substantial green roof, the daily energy demand for air conditioning is cut by 75%. Buildings are the largest contributor to carbon emissions, and Dwell reported that 50,000 buildings covering over 25,000 square feet in New York, which includes only 2% of the total buildings, contribute to half of all of the city’s building carbon emissions.
These roofs also help with storm water retention. Storm water run-off is a large contributor to waterway pollution, and during extensive rainfall, this problem only becomes worse. Green roofs have containers that hold water eventually to be used by the plants. The Cooper Union's “A New York City Guide to Green Roofs” states that green roofs retain 50-75% of the rainfall, and they can reduce street flooding and sewage overflow issues.
While the positive environmental impacts are important to the well-being of the city and its sustainability, another benefit is how implementing green roofs can improve the lives of the people who live there.
One of the largest problems people face in New York and other major metropolitan cities is the urban heat island effect. According to the Nature Conservancy, temperatures in cities can reach up to 22°F higher than the surrounding rural areas. As mentioned by the Nature Conservancy, according to the Centers for Disease Control and Prevention, heat waves are the deadliest natural disasters for Americans. These installations should lower roofs’ temperatures during the day, and the plants help cool the area by evapotranspiration. Dark rooftops are the problem because the exposed asphalt or tar increases this effect.
Besides helping to combat the heat island effect, green roofs can help with people’s well-being by decreasing noise because plants have many surfaces, so noise from the city or rooftop can be deflected and absorbed.
Green roofs contribute to improved air quality, increased insulation and energy efficiency that works to reducing greenhouse emissions. They will also help cities acclimate to more frequent and extreme weather conditions. If large enough, they can be places where food is grown, and jobs are created. At its most basic, these roofs can provide a habitable and open space in cities where open areas are at a premium.
Although these roofs use important space, they are a necessary improvement for cities looking to help the environment and residents.