'Cool roofs' could save your life – so why have you never heard of them?

Heat waves occur more often than they used to, according to the U.S. Environmental Protection Agency (EPA) . The 1960s saw an average of two heat waves per year. In the 2010s and 2020s, we averaged six a year. Heat waves have also been getting longer, more intense and deadlier.

How can people protect themselves from deadly temperatures without relying on increased energy expenditure from air conditioning? The U.S. Department of Energy's (DoE) Argonne National Laboratory (ANL) ran a large-scale simulation of the city of Chicago in 2023 to explore this question. Their answer? "Cool roofs." In the simulation, white-painted roofs decreased the near-surface temperature by 2.7º Fahrenheit (1.5º Celsius). Associated energy demand also dropped by a staggering 16.6%.

These findings suggest cool roofs may, in fact, be part of many of our futures. So why aren't people talking about them more?

What is a 'cool roof?'

Cool roofs use reflective roofing materials to reflect sunlight and absorb less heat than a traditional roof. Beyond that, however, the definition can get murky, according to Jeffrey Steuben, executive director of the Cool Roof Rating Council , which develops rating systems for cool roofs and walls.

"What constitutes 'cool' may be different for, say, Chicago, than Phoenix, Ariz.," Steuben said. And nuances may exist within each geographic region of the country. "In California, for example, the building code requires different solar reflectance values that range from 0.20 for steep-slope roofs to 0.63 for low-slope roofs."

A variety of materials can be used to create a cool roof, but all of them increase the amount of sunlight reflected. A white-painted roof, for example, reflects the most sunlight, but darker asphalt roofs with "cool-colored" granules also trap less heat. Wooden roofing materials are naturally cool-colored, and concrete or metal roofs can be painted to be more reflective.

A 2024 modeling project focused on London found that cool roofs outperformed green roofs (or roofs covered in plants), solar panels and street-level vegetation in city-air temperature reduction. A 2007 research study published in Energy and Buildings (using materials available in the mid-2000s) estimated that cool roofs could decrease cooling demand by up to 27%.

According to the EPA , cool roofs applied at scale could:

• reduce the cooling energy use across an entire city

• reduce the formation of ground-level ozone

• decrease air pollution and greenhouse gas emissions related to air conditioning

• equitably protect low-income and underserved populations that are more likely to be affected by "heat islands," or urban areas with tightly packed buildings and little green space

Interest, awareness around cool roofs are on the rise

Because of the variety of building codes that define cool roofs in different ways, it can be difficult to figure out just how many cool roofs already exist. However, Dr. Ronnen Levinson, staff scientist and leader of the Heat Island Group at the University of California's Lawrence Berkeley National Laboratory , points out that a 2018 survey found around 35% of commercial buildings had cool roofs. That number needs to be updated, but it provides a baseline estimate for how many buildings could already have cool roofs.

Steuben also said that while individual projects are nearly impossible to track, his Cool Roof Ratings Council has seen a "proliferation of codes and programs adopting cool roof provisions over the past few years," indicating increased interest in cool roof technology. (Check out the CRRC's list of codes and standards for more information about cool roofs in your area.)

Could a cool roof really save your life?

Decreased energy consumption and the associated cost saving are benefits for consumers,, but the stakes are a lot higher. The rising severity of heat waves is a serious concern as global temperatures spike and weather disasters become more common. How serious? The 2003 European heat wave caused an estimated 72,000 deaths, according to the United Nations (UN) , making it the sixth deadliest global disaster in 20 years.

Cool roofs could play a huge role in mitigating heat-related deaths around the world. A 2019 research study published in the research journal Environment International found that cool roofs could offset 25% of heat-related deaths due to urban heat island effects during a heat wave.

As roofing technologies improve, this number will only increase. What if you don't live in a city? Though much of the research on cool roofs is related to commercial buildings and the effect of large-scale implementation, cool roofs can have notable impacts on individual buildings, too. Anjali Jaiswal, of the Natural Resources Defence Council , told the BBC in a 2019 interview that a cool roof could reduce the interior temperature of a building by 3.6ºF to 9ºF (2ºC to 5ºC). That's a huge difference during a heat wave – one that could absolutely save lives at scale. In states such as Arkansas, Mississippi, and Louisiana, where temperatures are high and power grid stability is low, the impact could be significant.

The future of cool roofing

The Cool Roof Ratings Council has seen an increase in codes and standards related to cool roofing over the past few years, Steuben said, but getting more cool roofs in place will become increasingly important.

According to Dr. Levinson, the most important step is getting the word out. "Since there are high-performance cool solutions available for nearly all types of roofs at no extra cost, education and demonstration are central to cool-roof adoption."

Levinson also expects the next decade to see a proliferation of cool roof products available in different colors, including deep reds that stay as cool as white roofs and smart coatings that maximize energy savings throughout the year. "Cool walls," a category already assessed by the Cool Roof Ratings Council, will continue to grow in prevalence and importance, as well, he said.

Steuben paints a similarly forward-looking picture of cooling technologies, including cool roofs, cool walls, cool pavements, shade structures, and living roofs covered with vegetation becoming more important in managing building and city temperatures.

Levinson summed the whole movement up appropriately. "The future of roofing will be cool!" he said.