Kemri: White mabati will cool your house, block mosquitoes

The trial found that indoor densities of female Anopheles funestus -the mosquito most responsible for malaria transmission in the area -were 77 percent lower in screened houses than in unscreened ones.

While many Kenyans prefer dark roofs, scientists say white paint, along with other house modifications, is a sure way to keep the house cool while reducing malaria-carrying mosquitoes indoors.

The study, by researchers from the Kenya Medical Research Institute (Kemri), also found that adding screening on doors, windows and eaves, as well as low-cost mat ceilings, helped block mosquitoes and improve indoor comfort.

Kemri scientists set out to answer the question: Can an entire house function like a bed net, keeping mosquitoes out while remaining naturally cool? The new study answered that question affirmatively, showing that house modifications can both reduce indoor mosquito densities and lower household temperatures.

A common architectural approach to indoor cooling is the inclusion of openings on doors, windows and vents. But these openings also serve as entry points for mosquitoes. The researchers tested different modifications on 40 houses aimed at improving cooling and reducing mosquito entry.

Some houses received cool-roof paint (white reflective paint) on their iron roofs, others had locally made mat ceilings installed, while some were improved for cross-ventilation.

All intervention homes had screening on doors, windows and eaves to keep mosquitoes out. Screens are fine wire meshes fixed over doors, windows and the open spaces under the roof (eaves).

The cool-roof paint delivered striking results. The study showed that daytime indoor heat was reduced by 3.3°C and night-time temperatures fell by 2.4°C, compared with unmodified homes.

“By rethinking how we build our homes, we can protect families from the health threats of climate change while strengthening malaria control,” said Prof Elijah Songok, acting director general of Kemri.

“This research provides a clear pathway for policy, investment and large-scale implementation.” Titled ‘Housing modifications for heat adaptation, thermal comfort and malaria vector control in rural African settlements’, the study was published on Monday in the Nature Medicine journal.

“The application of white reflective coating on iron sheet roofs, which were the hottest part of the house during the day, effectively reflected solar radiation, reducing indoor mean temperatures by 2.8 ± 0.2 °C compared to control houses,” the study said.

Kenya has a malaria prevalence of about six per cent nationwide, while in the lake endemic zone it approaches 19 per cent. The disease kills about 10,000 Kenyans every year, the Ministry of Health says.

The trial found indoor densities of female Anopheles funestus—the mosquito most responsible for malaria transmission—were 77 per cent lower in screened houses than in unscreened ones. Nuisance-biting Culex mosquitoes were also reduced by 58 per cent.

“Our research proves that we don’t need expensive technology to dramatically improve health outcomes,” said Dr Bernard Abong’o, lead researcher at Kemri’s Centre for Global Health Research. “With materials that are affordable and locally available, we can create homes that stay cooler and keep mosquitoes out.

In effect, we have shown that it is possible to have a bed net for the entire house.” The idea behind house modifications is not new, but this study is one of the first in East Africa to test combined measures—cool roofs, ceilings and screening—under real rural conditions.

Screening doors, windows and eaves physically block mosquito entry, while reflective paint and ceilings reduce heat build-up caused by traditional dark or unpainted metal roofs that absorb heat.

In Kenya, many rural homes still use blue, dark or green mabati roofs, which trap heat and can make houses stiflingly warm at night, discouraging people from using bed nets on hot evenings.

The study also estimated the cost of modifications at around $189 (about Sh25,000) per house, depending on size and number of openings, which researchers say is within reach for many rural families or could be supported through community or government programmes.

Community members who participated in the study responded positively to the changes. About 85 per cent of households involved in the trial said they were willing to invest their own resources to adopt and maintain similar modifications in the future.

“These findings show that the benefits of healthy housing go beyond shelter,” Prof Songok said.

“In malaria-endemic, warming regions, simple modifications to housing can reduce disease risk and improve quality of life.”

Kemri urged the national and county governments to include cool-roof paint, screening and improved ceilings in building codes, malaria control strategies and climate adaptation plans, especially in high-burden regions.