Green Roof, White Roof, Blue Roof, New Roof! Save Money, Save the World

Green Roofs

Green roofs are those vegetated with plants and trees in soil substrate over a waterproof membrane. Their benefits include local cooling and decreased building energy use, storm water retention, greenhouse-gas absorption and the creation of an ecological habitat. They last twice as long as conventional roofs, cool the air and remove pollutants, and confer great economic benefit in the form of energy savings. The 14,000-square-foot green roof atop the residential Zeckendorf Towers in Union Square benefits property values and has the potential to capture 283,500 gallons of stormwater annually.

Although the average cost of a green roof in New York City is $18 to $20 per square foot, the city has developed a pilot program offering property-tax abatement for green roofs and solar energy systems effective through March 2013. To qualify, property owners must apply to the Department of Buildings (DOB) by March 15 for the abatement to take effect on July 1 of the same calendar year. Savings could equate to $4.50 per square foot.

White Roofs

White roofs seek to reflect incoming solar radiation instead of absorbing it, through the use of reflective materials on the roof surface, such as white paint. Benefits include reduced energy consumption and costs, particularly during peak demand, local cooling, and urban heat island mitigation.

A recent study released by NASA’s Goddard Institute for Space Studies found that white roofs reduced peak rooftop temperature in the summer by an average of 43 degrees (Fahrenheit). The city's volunteer clearinghouse New York City Service in partnership with  the DOB created the NYC °CoolRoofs program, which promotes rooftop cooling by identifying vendors who can supply rooftop coating at discounted rates.

Depending on material type, white roofs can cost up to $18 per square foot to install; however, a do-it-yourself acrylic paint option costs only 50¢ per square foot and shows good performance for a few years.

Blue Roofs

Blue roofs use technologies that regulate or capture and store stormwater runoff or slow its migration into the local sewer system. Compared to traditional roofs, blue roof technologies add only $1 to $4 per square foot.

Building owners can save on water usage costs and contribute to a reduction in localized flooding and combined sewer overflow events. For example, the rental building The Solaire in Battery Park City cites a 50 percent reduction in potable water use through its waste- and stormwater reuse system, which uses rainwater for toilet flushing, landscape irrigation, and heating, ventilating, and cooling (HVAC) towers. With current rates of $8.21 per 100 cubic feet (748 gallons) for combined water and sewer, owners could notice significant savings.

Using low-cost strategies to maintain resilient properties is the best way to meet the challenge of climate change in the 21st century.

Lesley Patrick is the program manager at the CUNY Institute for Sustainable Cities at Hunter College.

For more, join our Archive >>