How reflective roof paint is cooling homes across Africa

BY THE OPTIMIST DAILY EDITORIAL TEAM

The question seemed reasonable enough: what heat adaptation interventions were already working in Africa’s low-income communities? Lara Dugas, an epidemiologist, and climate scientist Mark New had received funding from the Wellcome Trust’s HeatNexus initiative to evaluate what was in place. When they went looking, they found nothing. “The initial grant call was to evaluate existing heat adaptation interventions in low- and middle-income settings,” Dugas says. “But we quickly discovered that there were no existing interventions in Africa to evaluate.”

So they built one. The project they created, Heat Adaptation Benefits for Vulnerable Groups in Africa, settled on a South African product called Rhinoluxe Heat Reflect, an infrared reflective paint originally made for commercial buildings, agricultural facilities, and chicken coops. It had to be locally manufactured, affordable, and scalable. Two years later, roofs had been painted across four sites: Khayelitsha, Cape Town’s largest township; Mphego village in rural South Africa; and Ga-Mashie and Nkwantakese in urban and rural Ghana.

What three summers of temperature data showed

Readings collected over three summers from 240 houses across the four sites found that painted roofs kept indoor spaces an average of three to four degrees Celsius (about five to seven degrees Fahrenheit) cooler during the hottest parts of the day. In Khayelitsha alone, thirty painted houses were measured against a control group of thirty unpainted ones.

For Sylvia, a 49-year-old single mother in Khayelitsha, the difference translates to something specific: her children can sleep. Her brick house had been a problem every summer, with the youngest crying from the heat and her two older children struggling to focus on schoolwork. “It’s still hot,” she says. “But we have our house cooler now and can comfortably be indoors when there is the scorching sun outside. My children sleep better. For me, that means everything.”

Why sleep is the health metric that matters

Dugas is clear about why sleep is the data point the project is watching most closely. Building a scientific link between hotter houses and chronic conditions like diabetes or cardiovascular disease would take decades. Sleep disruption shows up within the first season, and the body of evidence connecting poor sleep to poor health is already substantial.

“Better sleep isn’t just a nice-to-have,” she says. “Bad sleep has poor mental health outcomes, poor disease outcomes, and makes diseases that are already present, like hypertension, much worse.”

Bongani, a 42-year-old from Khayelitsha whose roof has not yet been painted, traces what the accumulation feels like. “Heat is the worst part of my day,” he says. “Our zinc houses trap heat even into the night. We can’t sleep properly, and you wake up already exhausted. The heat makes me feel tired and angry, and sometimes I cannot even think straight.” When the temperature gets too high, he walks to a friend’s house. The friend has a painted roof.

Measuring what anecdotes cannot prove alone

Quantifying the benefit has required more than a thermometer. Participants across all four sites are fitted three times each summer with sleep and physical activity monitors and core body temperature sensors. Small devices mounted on interior walls collect continuous readings. Air pollution is tracked by a second sensor in each home. Blood glucose, blood pressure, and urinalysis tests round out the picture.

“Anecdotal evidence only gets you so far,” Dugas says. “Someone can tell you they slept badly when it was hot, but it is important to quantify just how bad is bad?”

The climate context this sits inside

This research is running in a country where, according to a 2025 Lancet report, residents were exposed to an average of 13 heatwave days in 2024. Eighty percent of those days would not have occurred without climate change. The communities where the project is based are among the least equipped to absorb the added burden.

Where the project goes next

HeatNexus is funding nine projects in total. For Dugas, this one has reoriented what she thought her career was for. “It has been especially rewarding doing work with a direct and measurable impact,” she says. “When you paint a roof you can change people’s lives in an instant.”

Postdoctoral researcher Vuyisile Moyo has spent three summers on foot in Khayelitsha, walking between painted and unpainted houses, interviewing residents, and pulling sensor readings. His view of scale is practical. “In an ideal world, every one of these roofs would be painted,” he says. “But we should start by painting schools and clinics.”

The formal health data is still being compiled. What is already clear is that the gap the project set out to close, the absence of any evidence base for heat adaptation in Africa, now has a place to start.

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