Putting a value on cooler cities – why smart surfaces matter

One of the first things I noticed about Belgrade when I arrived there in 2001 was the tall, leafy trees all along the sidewalks. Even when the weather was hot, walking on the sidewalk was still pleasant because of the trees. And this is true in many European cities.

While these trees take time to grow, there are a great many such strategies that can make our cities cooler, and the Smart Surfaces Coalition has a long list. Things like cool roofs offer a very quick payback; other ideas like solar PV roofs, green roofs, and porous and high albedo pavements might take a little longer.

“Smart surfaces are a set of surface technologies that allow cities to better manage sun and rain. Smart surfaces not only reduce temperatures and flood risk, but they also save money and make communities more livable. Adopting smart surfaces across the United States would save over $650 billion, reduce summer heat, create over 250,000 jobs, improve health, and reduce smog and pollution,” it says.

In 2018, the coalition crunched numbers in Washington D.C., Philadelphia and El Paso and concluded that “smart surface technologies” could deliver roughly half a trillion dollars in net financial benefits nationally and specifically, $1.8 billion in Washington, D.C., $3.6 billion in Philadelphia and $540 million in El Paso over 40 years.

While many of the benefits they analyzed — preventing hospitalizations associated with extreme weather, mitigating economic losses when floods or heat waves make a normal workday impossible, cutting health costs in low-income neighborhoods — were long-term and systemic and perhaps not seen as so vital at that time, perspectives may be chBanging given this year’s incredible heat.

The coalition has just taken a deep dive look at Baltimore, where temperatures can rise into triple digits on the hottest days of summer and is among the worst in the US for intensity of its urban heat island effect. Baltimore “has largely covered itself in dark, impervious surfaces, resulting in increased summer heat, higher energy bills, more flooding and pollution and large structural inequities,’ the report says. Lower-income neighborhoods are often 10 degrees F hotter than wealthy green parts of the city.

“We can now quantify the benefits and demonstrate that it is in the entire city’s self-interest to redress this environmental injustice,” says lead author Greg Kats. “If a low-income community gets really hot and more polluted, that’s going to spill over into wealthy neighborhoods.”

Heat islands are strongly influenced by whether a surface reflects sunlight or absorbs and retains the sun’s heat. Lighter and more reflective surfaces can mitigate extreme heat, cool the surrounding environment and prevent flooding; solar rooftops, meanwhile, can harness sunlight for energy, reducing power consumption and aiding in efforts to cut carbon emissions. 

“City-wide adoption of Smart Surfaces is an overdue investment necessary for Baltimore to protect itself from accelerating climate change—and become the healthier, more resilient, and more just city it seeks to be,” the report says. Such strategies include reflective roofs, reflective roads, green roofs, porous surfaces, rooftop PV, and urban trees.

Baltimore has managed to increase its tree canopy from 28% to 29%, the report notes, but should aim to increase that to 40%

It is not just a matter of the city spending money – the report notes that this would be an investment that returns 10 times the original costs.

As well as reducing summer temperatures by between 2.5 degrees and 4.5 degrees Fahrenheit, adopting “smart” surfaces citywide scale could bring $13 billion in economic benefits over 20 years and would cut the city’s carbon emissions by 17 million tons, the report says.

Cooling the city by more than 4 degrees F also would protect its critical tourism revenue by making Baltimore cooler even as the world, and alternative tourism destinations, get hotter. “Avoiding 10% loss of summer tourism … would avoid $10 billion in lost tourism revenue, $1.2 billion in revenue to Maryland and $800 million in city revenue over 30 years.” 

Smart Surfaces has developed a cost-benefit analytical tool that allows Baltimore and any city that has the necessary data to see what the costs and benefits would be for each suggested idea. Look for example at replacing roofs covered with black tar, so they become cool roofs.

“Covering 80% of such low-slope roofs and 20% of steep-slope roofs with reflective material would cost $112 million, but could cool the city by 2.4 degrees and bring in $862 million worth of benefits over 20 years, thanks to energy savings, lower costs for water treatment and flood damage, and reduced health risks and heat-related deaths”.

If all the proposed solutions are adopted, the report estimates the city will add 3,600 jobs in the first 20 years and 78,700 “job-years” (the equivalent of one full-time job for one year) over three decades.

A key goal is to give city planners the information to make good decisions. The solutions aren’t new. Many cities have launched heat mitigation projects using reflective surfaces and shade structures including Philadelphia, El Paso, and Washington, D.C., but they have tended to be done at a small scale. Citywide efforts are needed in order to get meaningful results, Kats says.

While city credit ratings haven’t been affected by city climate adaptations in the past, this is going to change, the coalition says. “Our analysis demonstrates that cities that choose to not adopt smart surfaces will experience significantly increased climate related losses, increased risk of credit rating reductions, and associated increases in city borrowing costs. Over time, these combined threats will increase risk of insolvency for cites that do not adopt resilience strategies such as smart surfaces”