A project measuring how reflective paint reduces indoor temperatures is delivering tangible benefits across Africa, proving that sometimes the best technology is just a really good coat of paint.
The brick house Sylvia shares in a Western Cape township with her three children gets unbearably hot every summer, causing the youngest to cry and her older children to struggle with homework. Sylvia is not alone: according to a recent Lancet report, in 2024, people in South Africa were exposed to 13 heatwave days on average, of which 10.5 (80%) would not have occurred without climate change.
But summer is more bearable now that her asbestos roof has been painted with reflective paint. “It’s still hot,” says the 49-year-old single mother from Khayelitsha. “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.”
The evidence isn't just anecdotal: temperature data over three summers from 240 houses across Africa reveal painted roofs are on average 3-4°C cooler during the hottest time of day. The pilot project - the heat adaptation benefits for vulnerable groups in Africa (Habvia) - has collected testimonials that participants in cooler houses are sleeping better too.
“Better sleep isn’t just a nice-to-have,” says Lara Dugas, an epidemiologist and co-principal investigator. “Bad sleep has poor mental health outcomes, poor disease outcomes, and makes diseases that are already present, like hypertension, much worse.”
It would take decades to link hotter houses to illnesses like diabetes and cardiovascular disease, but disrupted sleep is a canary in the coal mine. Dugas cites a large body of work investigating this relationship in the US, Jamaica, Ghana, Seychelles and South Africa.
Sylvia’s home is one of 30 in Khayelitsha whose roof was painted, with a control group of 30 unpainted houses for comparison. Habvia is also underway in Mphego village in rural South Africa, and Ga-Mashie and Nkwantakese in urban and rural Ghana respectively, using the same methodology.
The goal is to understand health benefits of specialised reflective roof paint in different contexts (rural vs urban) and climates (temperate vs high heat and humidity).
Habvia is one of nine projects in the Wellcome Trust-funded HeatNexus. “The initial grant call was to evaluate existing heat adaptation interventions in low- and middle-income settings,” says Dugas. “But we quickly discovered that there were no existing interventions in Africa to evaluate.” So they created their own, settling on a South African product, Rhinoluxe Heat Reflect, an “infra-red reflective roof paint” made for commercial and agricultural buildings. “The paint had to be locally manufactured,” says Dugas. “Eventually we want to paint millions of roofs, so price and local sustainability are a big deal.”
Two years on, all the roofs are painted. “There are so many factors to consider when comparing indoor temperature data,” says postdoctoral researcher Vuyisile Moyo, perched on a wobbly municipal bin. “What are the walls made of? What’s the roof made of? Does it have a ceiling? How many people are sharing the space?”
Moyo focuses on people’s experiences while colleague Ebrahim Behardien collects environmental data. For the past three summers, they spend three days a week walking around Khayelitsha with research assistant Monwabisi Tyunthu. Behardien downloads temperature data from iButtons (sensors smaller than a penny) and air pollution readings from slightly larger devices.
Moyo and Behardien have forged bonds in the community. On the day the Guardian visited, they called on the family of a 49-year-old participant who had died the previous week. The visit is emotional: they are given the best chairs in a tiny room crammed with a dozen relatives, aged from two to 62, reminiscing over a shared bottle of Fanta.
Back at Habvia headquarters in a leafy Cape Town suburb, research assistants Nandi Sinyanya and Tabitha Cetyiwe do health checks on three women who have fasted for tests including blood glucose, urinalysis and blood pressure. The women are fitted with sleep and physical activity monitors, plus a core body temperature sensor recording data over the week. Everyone across all four sites undergoes these tests three times each summer. “Anecdotal evidence only gets you so far,” says Dugas. “Someone can tell you they slept badly when it was hot, but it is important to quantify just how bad is bad?”
Dugas, who has spent most of her career focused on obesity, says Habvia has opened new avenues. “It has been especially rewarding doing work with a direct and measurable impact. When you paint a roof you can change people’s lives in an instant.”
One man waiting for change is Bongani, a 42-year-old from Khayelitsha. “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. My roof has not been painted yet, but I sometimes visit a friend whose roof has been painted. It is cooler there, and when it’s too hot, I prefer going to sit at his house.” He adds: “Painting the roofs may seem like a small thing, but for us, it changes how we live.”
Hopefully this is only the beginning. “In an ideal world, every one of these roofs would be painted,” says Moyo from another wobbly bin. “But we should start by painting schools and clinics.”