How schools are being built for extreme heat - without aircon

• Heat threatens children's education
• Aircon fuels global warming
• Architects turn to passive cooling

LONDON - When prize-winning architect Francis Kéré was growing up in Burkina Faso he spent his schooldays in a gloomy classroom that was so stifling he says it would have been better suited to making bread than educating children.

Years later, while studying abroad, Kéré returned to his home village to build a light and airy school where children could learn in comfort despite temperatures that can hit 45 degrees Celsius (113 F).

But the Berlin-based architect did not use aircon. Instead he incorporated a host of cooling features into Gando Primary School that he has since applied to projects across Africa.

Kéré, who won architecture's highest honour of the Pritzker Prize in 2022, is among architects pioneering sustainable school designs for a warming planet.

"My own school was so hot it was hard to concentrate," he told Context. "So I wanted to build a school that would be comfortable and inspiring for children."

Studies from Brazil to Vietnam show heat significantly impacts learning. In a report last year, the World Bank warned that climate change was threatening educational attainment, creating an "economic time-bomb".

Experts say classrooms should be no hotter than 26 C.

In Gando, villagers were initially shocked when Kéré announced he would build the school from clay, but the material is a natural temperature regulator, absorbing heat during the day and releasing it at night.

Concrete and plate-glass may look contemporary, but Kéré said they make buildings hot, necessitating air conditioners.

This creates a vicious circle. Energy-intensive air conditioners, which expel hot air outdoors, contribute to global warming, which then fuels demand for more aircon.

Instead, Kéré uses passive cooling techniques.

Gando's classrooms have openings at both ends, generating cross-ventilation. An overhanging roof elevated above a perforated lower roof improves air circulation and shades the facade.

In Kenya, Kéré's design for a college campus was inspired by termite mounds, which use natural ventilation to regulate interior temperatures. Low openings on the buildings suck in fresh air while terracotta-coloured towers let hot air escape.

Social change

Some 8,000 km (5,000 miles) away in northwest India's Thar desert, temperatures reached 48 C this year. Vegetation is sparse, and sandstorms are common.

The Rajkumari Ratnavati Girls School, a large oval sandstone edifice rising from the Rajasthan desert, was designed by New York architect Diana Kellogg.

The building's orientation and shape allow prevailing winds to flow around the school, while lime plaster on the interior walls has an additional cooling effect.

Lattice walls, inspired by traditional Indian jali screens, accelerate airflow due to a phenomenon called the Venturi effect. The school also runs off solar power and harvests enough rainwater for its needs.

Temperatures inside are up to 10 C cooler than outside, contributing to high attendance, Kellogg said.

Like Kéré, she believes good architecture can encourage social change.

Rajasthan has the lowest female literacy rate in India, but Kellogg said the school's monumental scale sends a strong message about the value of girls.

"It has enhanced their standing in the community," she said. "The girls take pride in attending and call it 'The College'. When I visit, the boys say, 'Build one for us'."

Greening schools

Even temperate countries are looking at how to cool schools as climate change brings more frequent heatwaves.

Britain has said new school buildings should be future-proofed for a 4 C temperature rise.

Its draughty Victorian-era schools with big windows and high ceilings are better suited to heatwaves than newer schools designed to keep heat in.

But education does not just happen indoors. Playgrounds are also important for children's development, and many cities are trying to make them greener.

Urban areas can be 4 C to 6 C warmer than rural areas, but planting trees reduces temperatures through shading and the release of water vapour.

Paris aims to convert all asphalted schoolyards to green oases by 2050.

Another solution involves cool paint. While countries like Greece have long painted building roofs white, scientists are now working on high-tech coatings that could potentially outperform air conditioners.

Building with clay

From geothermal cooling technology to smart glass, engineers are developing increasingly sophisticated systems and products to control temperatures.

But German architect Anna Heringer said sustainable architecture meant working with local materials.

Heringer, who has designed schools from Bangladesh to Ghana, is known for building with mud - "a low-tech material with high-tech performance.

"If you ask farmers, they will tell you a mud house is cool in summer," Heringer said, adding that clay balances humidity, which exacerbates physical discomfort in extreme heat and cold.

"Architects often try to be way too technical, but sometimes the solutions are in front of us."

In Tanzania, villagers told her they built concrete homes for status, but went to mud huts to sleep at night.

Contrary to popular perception, clay walls do not dissolve in the rain, Heringer said. There are simple techniques to prevent erosion, and a natural crystallization process strengthens the walls over time.

"Clay has been branded as a weak material, but in every culture and climate we have mud buildings that are hundreds of years old," Heringer said, adding that schools she built 20 years ago have required little maintenance.

Some classrooms in her schools have solar-powered fans, but there is no aircon. Not only does it consume energy, but constantly switching between heat and cold can harm children's health, she said.

Kéré - whose international commissions include Benin's new parliament building and the upcoming Las Vegas Museum of Art – said his studio gets many inquiries about building with clay and passive cooling.

"There's a big shift," he said. "This would never have happened just a few years ago."

(Reporting by Emma Batha; Editing by Ayla Jean Yackley.)