Since 2016, San Antonio has replaced dark roofs on low-income homes with reflective shingles; the program was linked to lower attic temperatures and electricity use

Picture this: it's peak summer, your fan is running at full speed, and your electricity bill still looks like a phone number. Now imagine living under a dark, sun-soaked roof that turns your attic into an oven every single day. That was the reality for many low-income families in San Antonio, Texas, not long ago. Then the city tried a simple approach: swapping conventional dark roofs for light-colored, reflective ones. According to a 2018 University of Texas at San Antonio (UTSA) study of homes in the city's roofing program, during peak summer afternoons, attic temperatures dropped by an average of 10.1°F, while homes overall saw their Electricity Use Intensity fall by an average of 7.3%.

A city that knows what real heat feels like

San Antonio was the nation's fourth fastest-growing city by numerical population growth between 2023 and 2024, according to U.S. Census Bureau data, and about 17% of its population lives below the poverty line. On June 4, 2024, San Antonio recorded a heat index of 117°F, its highest on official record, measured by the National Weather Service. In 2017, the city committed by resolution to align with the goals of the Paris Agreement, a pledge it later formalized in 2019 as a citywide goal of carbon neutrality by 2050. For households already stretched by rent and food costs, a very hot summer can force difficult choices about air conditioning. This is the exact problem San Antonio tried to fix with a roofing program called "Under One Roof."


So, what exactly did they do?

Beginning in 2016, the city started replacing the old roofs of homes of low-income families, senior citizens, veterans, and people living with disabilities. Instead of standard dark shingles, the city used Owens Corning reflective shingles in Shasta White, along with a radiant-barrier underlayment. In other words, these materials reflect sunlight rather than absorbing it. The program has grown from a $200,000 pilot in a single city council district in 2016 to a citywide initiative with a $2.25 million budget expansion approved in 2018, and more than $5 million in combined public and private funding by 2020. Under the program's official rules, the city places a five-year restrictive covenant on each property, requiring homeowners to keep owning and living in the home for five years afterward, which keeps homes affordable and protects families from being displaced.

Why a lighter roof makes such a big difference

It's more than just a hunch in San Antonio. Dark roofs absorb solar rays, turning them into heat that transfers into the building below. Reflective roofs, by contrast, send more of that solar energy back to the sky, so less heat enters the building and the air conditioner does not have to work as hard. This basic mechanism has been documented elsewhere too: a Lawrence Berkeley National Laboratory study of two small buildings found measurable electricity savings after their roofs were painted white, though at a much smaller scale than San Antonio's residential program. That may be why San Antonio's own electricity use intensity, measured per square foot, decreased by 7.3% after the roof replacements.

Heat isn't shared equally, and that's the bigger story

Not all neighborhoods receive the same amount of heat within the same city. A 2020 study published in the journal Climate by researchers Jeremy Hoffman, Vivek Shandas, and Nicholas Pendleton looked at 108 American cities and found that in 94% of them, neighborhoods affected by 1930s housing discrimination, known as redlining, are still warmer than other neighborhoods. Some cities had a temperature difference of up to 7°C (12.6°F), while the average difference between these neighborhoods was 2.6°C (4.7°F) across all 108 cities examined in the study. The same researchers point out that this gap is partly explained by less tree canopy and more paved, impervious surface in these neighborhoods. San Antonio's program targets high-heat, low-income areas, which makes its results especially relevant.

Why this should matter to us, not just Texas

Cities around the world are becoming warmer, and low-income neighborhoods often feel it first because older buildings can have dark roofs that trap heat. San Antonio's approach offers a low-tech model that other cities could adapt. A lighter shingle or a coat of reflective paint isn't glamorous, but it can lower indoor temperatures and electricity bills for the people who can least afford them. San Antonio's project suggests that small-scale interventions can make a difference for those who need it most. In this case, at least, part of the solution really was as simple as picking a different color for a roof.