Roofs of Earth, Seven Degrees Cooler

Across the Sahel the aspirational roof is imported sheet metal, which bakes the room beneath it and has to be bought with cash. The Nubian Vault is the older answer: an arched roof of sun-dried earth bricks, raised without formwork or timber, using a technique from Upper Egypt that Association la Voûte Nubienne revived, simplified and standardised so it could be taught quickly. Buildings roofed this way run roughly 7°C cooler than their metal-roofed neighbours, and every material comes from within walking distance. Founded in 2000 by the French mason Thomas Granier with Seri Youlou in Burkina Faso, AVN has trained masons and enabled more than 7,000 buildings across Burkina Faso, Mali, Senegal, Mauritania, Ghana and Benin — deliberately building a market rather than a donor programme, so masons earn a living from the skill and clients pay for the houses.