A University of Cape Town-led project is testing heat-reflective roof paint to cool homes and protect the health of low-income African communities in a warming world.
‘Everyone deserves a safe place to sleep at night that is not detrimental to their health,” Professor Lara Dugas, the co-principal investigator in the University of Cape Town’s Heat Adaptation Benefits for Vulnerable Groups in Africa (Habvia) project, told Daily Maverick.
Using reflective cooling paint on rooftops is one of Habvia’s heat adaptation interventions in a three-year controlled clinical trial, led by researchers in South Africa and Ghana, to test low-cost heat adaptation solutions in some of Africa’s hottest and most vulnerable communities.
The study uses both climate and health sciences to address and monitor the risks that extreme heat poses to human health in communities where heat-related health risks are exacerbated by socioeconomic vulnerabilities.
Threat of heat exposure
Africa is warming at twice the global average, and heat exposure is emerging as a major health threat, especially for people in low-income informal and formal housing, which can trap heat during the day, preventing cooling at night.
The Habvia project, funded by the Wellcome Trust, is testing passive cooling solutions such as reflective roof paint that cool indoor temperatures, where heat stress disrupts sleep and health most.
“When people don’t sleep well, they face additional challenges as a consequence of lowered immune function, as well as a higher risk for noncommunicable diseases like cardiovascular disease, hypertension, type 2 diabetes and chronic kidney disease.
“They also have a much higher risk of experiencing mental health challenges,” Dugas said.
The team chose to focus on sleep also because it was relatively easy to monitor in the home setting with the progression of technology, such as sleep monitoring devices.
“We have anecdotal evidence that the residents are feeling lower heat stress and greater comfort, through informal comments they have made. We still need to undertake a systematic assessment of their perceptions, to confirm these initial reports,” Professor Mark New, co-principal investigator of the Habvia project, told Daily Maverick.
New said the team had just finished collecting the data for the first hot season after roof painting, and they expect to have initial results by the middle of the year, once they have quality-controlled the data and done initial analysis.
Data from similar roof-cooling experiments in other parts of the world suggest indoor temperatures could be reduced by between 3°C and 6°C, said New. This could dramatically reduce the impact of heat-related health issues on residents.
New said one of his master’s students at UCT had just finished her dissertation, in which she has shown, using the data collected in the baseline monitoring period before roof painting, that the internal temperatures of the low-income formal and informal houses in Khayelitsha, Cape Town, reach dangerously high levels during the day.
And, there had been an increasing frequency of such temperatures over time, some of which could be attributed to climate change.
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Painting the rooftops and community involvement
Dugas explained: “Whenever you do an intervention, you want to make sure the intervention is identical in each of the four sites. The four sites that we are using are in South Africa and Ghana. And in each country, we have both an urban setting and a rural setting.”
She said this was important because urban settings, such as in Khayelitsha, are characterised by very high urban density with very little green space. Similarly, the research site in Ghana is in the coastal Ga-Mashie community in Accra, which also has a very high urban density, with very little green space and trees.
There are also two rural sites. In South Africa, it is Mphego Village, Limpopo, and in Ghana, it is Nkwantakese, about 25km outside Kumasi.
Before the painting was rolled out in four research communities, Dugas said they held workshops introducing the paint to research participants to explain what it was and what was in it.
“We then did demonstrations. We allowed participants to work with the paint to see that it wasn’t something toxic or harmful to them… And then, when we rolled out the intervention in each of the four communities, we worked with community members who then assisted us to paint the roofs.”
The team said that part of Habvia’s approach was to ensure these adaptation interventions involved members of the communities in the design and implementation, in the hope that it would ultimately be a sustainable solution.
“The main reasons we trained and employed local residents to do the painting were to create a sense of ownership in the experiment and to provide some (albeit short-term) employment opportunities,” New said.
From the few visits after the painting process, Vuyisile Moyo, a postdoctoral research fellow at UCT working on Habvia, said residents’ response to the paint was largely positive, with many appreciating the immediate reduction in indoor temperatures and good-quality sleep.
Dugas said they worked with the Community Organisation Resource Centre (Corc), a Slum Dwellers International affiliate, to foster an inclusive adaptation strategy, since they work in South Africa and Ghana.
“They liaise with the community ward counsellors because you can’t just come in there and start painting houses, right? Corc was amazing in facilitating the interactions with the ward counsellors,” Dugas said.
An extreme health problem
The researchers said temperatures across Africa are expected to rise up to twice the rate of mean global temperatures, posing significant health threats to vulnerable communities.
Africa being disproportionately affected by climate change, has been repeatedly reported by the World Meteorological Organization (WMO), which found that the rate of temperature increase in Africa has accelerated in recent decades, with weather- and climate-related hazards becoming more severe
“We will face the brunt of climate-related hazards globally, and we are not in any way set up,” Dugas told Daily Maverick.
This was why there had been a need to implement solutions to the African heat problem.
“Heat is an extreme health problem… Then when you add in floods, you get new malaria outbreaks, [and] cholera because of water-borne diseases. It starts to spiral very quickly.”
The prolonged exposure to high day and nighttime temperatures has been implicated in myriad adverse health outcomes, according to the Habvia researchers.
They said the built environment and inadequate housing can exacerbate these consequences, prompting the need to evaluate heat adaptation interventions as a sustainable adaptation strategy for low-income and informal settlement dwellers.
This was what the Habvia project aims to do, by assessing the impact of passive cooling interventions in homes on several key physiological and mental health outcomes, as well as the home’s internal thermal conditions.
One of the aspects they were focusing on was sleep health and sleep behaviour because Dugas said that disrupted sleep was a major risk factor for noncommunicable diseases as well as mental health challenges, including depression.
The team is conducting health monitoring for 240 participants (60 per site) over three hot seasons, who are split into intervention (cooling solutions) groups and control groups.
During the hot season, 60 participants at each study site go through three nonconsecutive weekly rounds of health monitoring. This comprises a clinic visit, where participants complete anthropometric assessments, blood glucose tests, urinalysis, blood pressure measurements and kidney function evaluations.
They are then fitted with wearable devices that track sleep, physical activity and skin temperature as they go about their daily routines at home.
While this takes place, the team is also measuring the temperature and humidity levels inside the participants’ homes.
Dugas said: “We check how their kidneys are working because chronic dehydration can damage your kidneys. We measure the temperature of their bedroom because we want to associate that indoor temperature with how you sleep. And we’re hoping that the indoor temperature will be lower in the houses that have now got the cool reflective paint.”
In South Africa, Dugas runs the Khayelitsha site, and Dr Thandi Kapwata from the South African Medical Research Council runs the site in Mphego. In Ghana, Professor Ama de-Graft Aikins from the University of Ghana runs the site in Ga-Mashie, and Professor Kweku Bedu-Addo from the Kwame Nkrumah University of Science and Technology runs the Nkwantakese.
“All of us have been working in these communities for at least 10 years,” Dugas said.
Challenges in the project
As for how durable the heat-reflective paint was, New said the manufacturer indicated that the paint could last up to 10 years. However, the team was sceptical about this and was measuring the deterioration in the paint during the experiment.
“We suspect it might be much shorter, given what other studies have reported. There is also the question of keeping the roofs clean – dust and dirt accumulating can also reduce the effectiveness of the paint. We are hoping that rainfall will do the job for us, but again, we are monitoring this through the project to see what maintenance might be needed,” New said.
New said a lot of the work on climate change at UCT, in both the African Climate and Development Initiative and the School of Public Health, was focused on those most vulnerable and least able to adapt to climate stresses.
“People living in low-income homes are especially vulnerable, firstly because their homes are often not very well constructed and so heat up and cool down rapidly, and second because they do not have many financial resources to reduce heat stress in their homes,” he said.
Roof painting was seen as a simple, relatively inexpensive option that, if effective, could make a huge difference to heat stress and health for relatively little cost.
In addition, New said the fact that funding agencies like the Wellcome Trust were now supporting research on climate and health meant that there was an opportunity to propose this project to them for financial support.
One of the key objectives of the project was to provide evidence on whether this was an adaptation that works, on its costs and benefits, and whether the model could be scaled up.
“Scaling these kinds of adaptations widely can be difficult, and requires a mix of champions to help scale it, a critical mass of people adopting it, and in low-income communities, some form of financial support to make the up-front costs affordable.”
Part of the research was coming up with recommendations for how this scaling could be achieved.
This article was first published on Daily Maverick and was written by Kristin Engel.
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