Cooling Urban Heat Islands with ‘Smart Surfaces’
Green Roofs, Porous Pavements Cut Heat, Emissions and Credit Risks
Speakers at an Atlantic Council webinar on smart surfaces say that greening roofs and sidewalks should be an integral part of Biden’s infrastructure plan.

Take a look at two maps of the nation’s capital: one charting upper- and lower-income neighborhoods, and one charting surface temperatures in those areas. An unsettling pattern emerges.

Wealthier areas of D.C. are cooler than lower-income areas, where asphalt, concrete and the lack of trees and green space create heat islands, with temperatures potentially 10 to 15 degrees higher than neighborhoods with tree-lined streets and parks.

Smart Surfaces
Temperatures in low-income areas of a city, like D.C., can be 10 to 15 degrees hotter than in well-off neighborhoods. | Smart Surfaces Coalition

“We’ve spent two centuries as a country mistreating low-income areas and making them miserable and hot and polluted. It’s time to change that, and we know how to do it,” said Greg Kats, founder and CEO of the nonprofit Smart Surfaces Coalition (SSC). Kats and the coalition are passionate promoters of a range of “smart” urban technologies — green roofs, porous pavements and community gardens — and the multiple benefits they offer low-income communities.

He and other speakers at a recent Atlantic Council webinar on smart surfaces believe that greening city roofs, sidewalks and other street-level infrastructure should be an integral part of President Biden’s $2 trillion infrastructure plan.

“Adopting cooler surfaces and smart surfaces, you bring down energy bills, which are a very large part of the disposable income of people who are less well-off,” Kats said. “You’re improving air quality and decreasing flooding and risk, and those have real costs.”

A recent study co-authored by Kats and posted to the SSC website suggests that adopting smart surfaces can reduce cities’ risk to extreme weather events and thus improve their credit ratings and access to low-cost capital.

Other research has firmly established the connections between dark urban roofs, roads and other surfaces, and a number of health, environmental and equity concerns, said Jennifer Roberts, the former mayor of Charlotte, North Carolina. “In hotter areas, there are more incidents of aggression and violence,” she said. “We know that children don’t learn as well. We have documented research showing that learning goes down and test scores go down. We know that in our public schools, 40% of them don’t have air conditioning.”

Similarly, the impact of smart surfaces on individual and community health is huge, said Surili Patel, director of the American Public Health Association’s Center for Climate, Health and Equity.

“Decreasing urban heat and flooding while improving air quality [can] have the largest benefits not just across the low-wealth neighborhoods but across the entire city, making a city more equitable and livable, not to mention improving social cohesion and building avenues to psychosocial resilience,” Patel said. “It’s hard to overstate these interconnections between climate change, health and equity.”

Hiding Behind Air Conditioning

The basic idea behind smart surfaces, said Kats, is that cities have done a “terrible job” of managing the sunshine and rain that are part of the urban environment. Dark, impermeable surfaces raise temperatures and cause run-off, pollution and contamination, making many U.S. cities generally unlivable during the summer months, he said. Furthermore, most infrastructure managers or city planners make decisions based primarily on cost.

“We hide behind air conditioning,” Kats said. “Smart surfaces are saying, look, the selection that we make on our surfaces — is it a green or dark surface, does it reflect sunlight back into space or absorb all the heat — those design choices have not been conscious choices. We can do better.”

The SSC website particularly calls out “cool roofs” that are light colored and reflect light back into the atmosphere rather than absorbing it; porous, permeable pavements that avoid runoff and flooding and recharge ground water; and green roofs, covered in vegetation, that lower building costs, pollution and greenhouse gas emissions.

Solar panels and urban trees are also included, and the group has developed a cost-benefit tool for calculating the long-term savings possible for cities adopting a mix of smart surfaces.

Smart Surfaces
| Shutterstock

“When you look at smart surfaces through a city lens, it’s correcting that long-term structural injustice,” Kats said. “Some of the communities we’re working with have 5% tree cover, which means kids are not in shape. They don’t see birds. They don’t play on grass, and that’s wrong.”

Similarly, Roberts sees green space and smart surfaces addressing multiple community needs. Parking lots turned into community gardens can not only help lower temperatures and pollution, but also provide fresh food in inner-city food deserts, she said.

She also emphasized the need for public-private partnerships. The private sector has “a lot of surfaces as well, a lot of private parking lots and parking decks” that should be considered in climate risk assessments, Roberts said. “A lot of cities have reworked the way they require developers to put grass islands in the middle of parking lots and have certain impermeable surfaces that are reflective.”

Community engagement at all stages of planning and decision-making is also imperative, particularly to ensure that upgrading community infrastructure does not result in higher property values and residents being priced out of their neighborhoods, Roberts said.

“We have to be conscious about eco-gentrification,” she said. “But there are solutions. I’ve seen low-income housing with solar panels on the roof, gardens in the back. We can absolutely walk and chew gum at the same time.”

Biden’s American Jobs Plan does not specifically designate ­­smart surfaces for federal programs and funding. But the plan includes $213 billion to “produce, preserve and retrofit more than 2 million affordable and sustainable places to live,” as well as money for retrofitting schools, Veterans Administration hospitals and federal buildings — all potential opportunities for incorporating smart surfaces.

Roberts sees the plan’s community block grants as an effective means for getting federal money to a range of infrastructure projects, including smart surfaces, that are developed by and benefit local communities.

Kats is hopeful that the plan will give “cities for the first time the opportunity … to make a conscious decision about their surfaces. We want green surfaces so that the air is clean; we want trees so that people get shade, and they can be outside in a vibrant environment. So, build back better; it really starts with saying, ‘We have a choice.’”

District of ColumbiaFederal PolicyState and Local PolicyTechnology

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