Technologies are helping cities and neighborhoods beat the heat

Some of these technologies have been around for more than a decade but are seeing greater demand as global temperatures rise. For example, Washington, D.C., has built more than 3,200 green roofs covering 9 million square feet, compared to about 300,000 square feet in 2006, according to federal and city officials.

Other technologies, such as ultra-reflective coatings for sidewalks, streets, and windows, are becoming effective and affordable enough for widespread use.

Los Angeles’ Pacoima neighborhood, a densely populated location wedged between freeways and an industrial district, has partnered with GAF, a New Jersey-based roofing manufacturer, to paint a basketball court, a local park, and neighborhood streets with a reflective coating.

“There is a lot of asphalt and a lack of investment in tree canopies,” said Melanie Paula Torres, 24, a community organizer with the Pacoima Beautiful group. “Considering the fact that we are in an industrial area, this contributes to urban development.” The heat island effect.”

The reflective coating lowered air temperatures in the test area 6 feet above the ground by 3.5 degrees Fahrenheit during extreme heat days, and surface temperatures by 10 degrees, according to Jeff Terry, GAF vice president of corporate social responsibility and sustainability.

Hot conditions are worse in urban heat islands, which can be up to 10 degrees hotter than the surrounding suburbs, and occur when buildings, roads and other infrastructure absorb and re-emit the sun’s energy.

Cooling techniques mitigate this. Green roofs absorb heat before it can penetrate the buildings below. Ultra-reflective coatings reflect visible sunlight and invisible infrared radiation away from surfaces to keep them cooler. The ultra-white coating developed at Purdue University promises more protection, though the product is not yet commercially available. Each strategy helps reduce energy use.

“The important thing is helping people affordably cool their homes and workplaces,” said Jane Gilbert, chief heat officer for Miami-Dade County, which has seen a record 46 consecutive days of heat index above 100 degrees this summer. The more efficient our buildings and air-conditioning systems can be, the less we contribute to the greenhouse gases as well as the waste heat that goes to our urban heat islands.

Miami is one of the cities most vulnerable to the urban heat island effect, along with San Francisco, New York, Chicago and Seattle, according to an analysis by Climate Central, a New Jersey-based nonprofit organization that researches the effects of climate change. Its analysis found that 41 million people living in 44 cities experience an urban heat island effect of at least 8 degrees. Nine US cities had at least 1 million people exposed to urban heat of 8 degrees or higher due to the local built environment.

To combat the heat, some cities are taking advantage of federal funds and other incentives to persuade local builders to convert office buildings to greener, cooler places.

And in Miami-Dade County, officials used federal funds to outfit 1,700 public housing units with new, low-energy air-conditioning units. Local officials also introduced a successful amendment to Florida’s building code that would require cool reflective roofs on all new commercial buildings starting in 2024, and they enrolled 150 buildings in a voluntary energy audit program to track improvements to cut energy use and keep temperatures low.

New York, Chicago, Philadelphia, Toronto and other cities are promoting green roofs through tax credits and other incentives in an effort to lower energy bills and lower ambient temperatures, according to Stephen Beck, president of Green Roofs for Healthy Cities, a Toronto-based organization. Green Roof and Wall Industry Association. Beck said green roofs can be 30 to 40 degrees cooler than roofs of a similar size, while reducing waste heat from air conditioning units.

And in the Pacoima neighborhood of Los Angeles, Torres says residents have told her the streets and playgrounds have gotten cooler since the reflective paint was completed in August 2022.

“The first thing that always appears are heat waves when you look out on the street. They don’t see it anymore,” said Torres.

The next step is to install reflective roofing materials on a few homes as part of the neighborhood’s cooling efforts. “We want to continue to aggregate solutions to create an overall great community with multiple strategies,” said Torres.

Changing the urban landscape to adapt to the extreme heat takes money and technical knowledge, according to city leaders and academic experts. But they also recognize the need to keep people safe as global temperatures rise.

“No single solution will necessarily be able to address the entire problem, but by systematically applying solutions that work on a site-by-site basis, we can make a difference to the urban heat island effect,” said David Sailor, a professor of geography. Science and Urban Planning at Arizona State University.

Write to Eric Niiler at eric.niiler@wsj.com