Researchers are collecting data from monitors inside houses and conducting health tests on participants to determine whether reflective white paint effectively reduces indoor temperatures. A project measuring how reflective paint lowers indoor heat is delivering tangible benefits across Africa.
Better Sleep, Improved Health, Happier People
The brick house Sylvia shares with her three children in a Western Cape township on the outskirts of Cape Town becomes unbearably hot every summer, causing her youngest to cry and her older children to struggle with homework. Sylvia is not alone. According to a recent report in the Lancet, in 2024, people in South Africa experienced an average of 13 heatwave days, of which 10.5 (80%) would not have occurred without climate change.
Summer is now more bearable for Sylvia's family since her asbestos roof was coated with reflective paint. “It’s still hot,” says the 49-year-old single mother from Khayelitsha, the largest township in the city. “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.”
Evidence from 240 Houses
Temperature data collected over three summers from 240 houses across Africa reveals that homes with painted roofs are on average 3-4°C cooler during the hottest part of the day. The pilot project, called Heat Adaptation Benefits for Vulnerable Groups in Africa (Habvia), has gathered testimonials indicating that participants in cooler houses are sleeping better.
In Khayelitsha, 60 houses were monitored: 30 with painted roofs and 30 without. “Better sleep isn’t just a nice-to-have,” says Lara Dugas, an epidemiologist and principal investigator of Habvia alongside climate scientist Mark New. “Bad sleep has poor mental health outcomes, poor disease outcomes, and makes diseases that are already present, like hypertension, much worse.”
While linking hotter houses to illnesses such as diabetes and cardiovascular disease typically takes decades, disrupted sleep patterns serve as an early warning sign. “We know that poor sleep leads to worse health outcomes,” says Dugas, citing research from the US, Jamaica, Ghana, Seychelles, and South Africa.
Methodology and Goals
Sylvia’s home is one of 30 in Khayelitsha with painted roofs, compared to a control group of 30 unpainted houses. Habvia is also being conducted in three other African communities: Mphego village in rural South Africa, and Ga-Mashie and Nkwantakese in urban and rural Ghana, using the same methodology. The goal is to understand the health benefits of specialized reflective roof paint in different contexts—rural versus urban—and climates—temperate versus high heat and humidity.
Habvia is one of nine projects funded by the Wellcome Trust under the HeatNexus initiative. “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 roof paint and choosing 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.”
Data Collection and Community Bonds
Two years on, all roofs have been painted. Postdoctoral researcher Vuyisile Moyo, while inspecting a corrugated-iron shack’s roof, notes: “There are so many factors to consider when comparing indoor temperature data. 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 three summers, they have spent three days a week in Khayelitsha, alongside research assistant Monwabisi Tyunthu, who lives in the township. Moyo and Tyunthu conduct interviews, while Behardien downloads temperature data from iButtons—sensors smaller than a penny hanging on walls—and air pollution readings from another device.
The team has built strong community ties. During their work, they chat with participants and neighbors. On the day of a visit, they called on the family of a 49-year-old participant who had died the previous week. The visit was emotional: Behardien and Moyo were given the best chairs in a tiny room filled with a dozen relatives, aged two to 62, as they reminisced over a shared bottle of Fanta.
Health Assessments
Back at Habvia headquarters in a leafy Cape Town suburb, research assistants Nandi Sinyanya and Tabitha Cetyiwe conduct health checks on three women participants. After fasting for tests including blood glucose, urinalysis, and blood pressure, the women enjoy a sandwich and tea. They are fitted with sleep and physical activity monitors, along with a core body temperature sensor, which will record 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.”
Future Hopes
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.” Moyo hopes this is just the beginning. “In an ideal world, every one of these roofs would be painted. But we should start by painting schools and clinics.”
The study’s participants asked to be identified by their first names only.
