How ‘Cool Roofs’ Can Help Fight Climate Change

Painted rooftops reflect the heat instead of absorbing it, reducing the need for air-conditioning and cutting greenhouse gases.

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Last summer, New York City endured three heat waves and many days when the temperature climbed above 90 degrees. In some neighborhoods, like the Hunts Point section of the South Bronx, which ranks as one of the city’s most vulnerable areas to heat, extreme temperatures actually linger, contributing to increases in heat-related illness and deaths.

This sweltering effect can be attributed to the built environment, with its lack of protective tree shade and swarms of traffic and surroundings cramped with glass, asphalt, metal and concrete. Installing cool roofs, which involves lightening the surface color of rooftops to reflect and not absorb heat, can temper excessive heat from the top down and reduce the urban heat island effect — a common and adverse consequence of climate change where air temperatures are significantly higher in a city than in surrounding areas, even at night.

The Hunts Point Produce Market, the country’s largest wholesale produce market and a longtime mainstay in the borough, took a step toward climate action in October, coating about 30,000 square feet of its dark 800,000-square-foot roof with a material known as Elasto-Kool 1000, a white paint infused with silicone to reflect solar heat and UV rays and decrease indoor and surface temperatures during summer months.

The coated roof is expected to help cut down on the energy use for air-conditioning, reducing the amount of greenhouse gases expelled into the atmosphere. The remainder of the roof is expected to be coated in 2022 or later, depending on the availability of funds.

The project was part of the city initiative NYC CoolRoofs and was being completed by workers of the HOPE Program, a nonprofit organization which provides job training and professional development resources to New Yorkers seeking opportunities in climate-focused industries. To date, CoolRoofs, in partnership with city agencies and grant funding from the Environmental Protection Agency, has covered more than 10 million square feet of rooftops since 2009.

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The Hunts Point Produce Market in the South Bronx is the country’s largest wholesale produce market.Credit…Hiroko Masuike/The New York Times

“We are making an impact on the environment and on people’s individual lives,” said Zakiyah Sayyed, 36, who resides in the South Bronx and is a crew supervisor for the Hope Program. “We have projects all across the city, so I can see the impact that we are making in NYC.”

“Rooftops present an important opportunity to both mitigate and adapt to climate change, and to address a range of environmental and social issues,” said Emily Nobel Maxwell, the cities director for the Nature Conservancy in New York.

Combining different roofing types with reflective coatings and solar panels can boost energy benefits. A new 11,500-square-foot “green roof” at 399 Sands Street in the Brooklyn Navy Yard features a mix of sedum and wildflowers, and its effect is augmented by a white cool-roof system by Siplast, a commercial manufacturer. It is atop a property owned by Steiner NYC and was installed by Brooklyn Grange, an organization that designs and maintains green roofs, featuring vegetation, and rooftop farms. “Every roof has the potential to help solve the climate crisis,” said Gwen Schantz, Brooklyn Grange’s co-founder and chief creative officer.

The de Blasio Administration launched Cool Neighborhoods NYC, furthering a strategy that would focus on locations with the highest scores on a heat vulnerability index, such as some neighborhoods in Brooklyn and the Bronx.

Under the 2019 Climate Mobilization Act, New York City mandates that new roofs feature reflective surfaces and, if eligible, solar panels or a green-roof system. The NYC CoolRoofs program, which supports the city’s goal to reduce carbon emissions by 80 percent by 2050, offers free installations on affordable housing and buildings that house nonprofits, and low-cost installations to other buildings willing to cover the cost of coating materials.

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At 399 Sands Street in the Brooklyn Navy Yard, elements of a green roof and cool roof work in tandem to help reduce the urban heat island effect. Credit…NYC Department of Environmental Protection

The New York City Housing Authority, the public housing agency that is the largest landlord in the city, expects that 2,300 of its 2,500 buildings will have cool-roof features in place in the next few years. “To date, 623 cool roofs have been installed along with full-roof replacements that are more effective at insulating the apartments below them,” said Rochel Leah Goldblatt, deputy press secretary for NYCHA.

Though cool roofs are often associated with large buildings, such as Ford Field, the 340,000-square-foot domed football stadium in downtown Detroit, reflective materials such as paint, shingles, tiles or specialized metal sheets, can be installed on private homes.

Costs will vary depending on the location, condition of the roof and materials required, but compared to traditional roofing products, cool roof coatings can run up to 20 cents more per square foot, according to the Environmental Protection Agency. On hot summer days, cool roofs can reduce air-conditioning costs by 10 percent to 30 percent, according to NYC CoolRoofs.

The Cool Roof Rating Council, an independent nonprofit based in Portland, Ore., that evaluates the reflective performance of roofing products, said there are rebates and incentives for cool roofs and other energy-saving projects, searchable via their site, coolroofs.org, or on dsireusa.org, the Database of State Incentives for Renewables and Efficiency.

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Part of the roof of the Hunts Point Produce Market received a coating of reflective paint in October to improve energy efficiency. Credit…Hiroko Masuike/The New York Times

Jeffrey Steuben, executive director for the council, noted that cool roofs need not be covered in white; alternative hues for the coating include gray and terra cotta, among others. The council said it would begin a similar review program dedicated to products for vertical surfaces in January 2022. “There are a growing number of codes and programs that are specifying solar reflective walls,” Steuben said.

For now, there’s ample real estate in New York that can be evaluated for a cool-roof makeover ahead of next summer, said Ms. Nobel Maxwell of the Nature Conservancy. “There are more than a million buildings in New York City that, in total, have about 40,000 acres of rooftops, which is about the size of a whole additional borough.”

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