Clay walls have a high thermal inertia. This means that they act as a climate buffer that creates a thermal delay in the flow of heat from the outside to the inside, absorbing it during the day and releasing it overnight. The material is especially suitable for hot and dry climates, such as that of Gando, where Francis Kéré built his first school. After years of studying abroad, Kéré returned to his home community with the intention of building this school with the same materials historically used by locals, which many originally viewed as strange, as he said in this lecture. Despite the initial prejudice, it was the combination of local materials and techniques with Kéré’s acquired knowledge that ultimately gave strength to the project.
Providing thermal comfort without the help of electrical devices in an extreme climate like Burkina Faso requires some very well thought-out passive strategies. First, it is essential to provide abundant natural ventilation. In the case of the Primary School and its subsequent expansion in Gando, all classrooms have openings at both ends, generating cross ventilation. Also, by creating small openings in the ceilings, the warm, lighter air rises, creating an air flow that cools the room. And through a free space between the walls and the metallic roof, heat from the metallic tiles is reduced and air circulates from the inside to the outside, creating a comfortable environment for children to learn. Therefore, these coverings not only protect the building from the sun, but also from occasional heavy rain, hence protecting the materials from the weather. Beyond aesthetics and performance, the metallic tiles were chosen because they are available locally – as well as the rebar structure that sustains them –, a guiding principle that characterizes Kéré's work wherever he goes.
