- 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.
Intermediate spaces and skylights
Gando Primary School Library. Gando, Burkina Faso
Apart from Gando Primary School, most of Kéré’s projects use local materials in smart and innovative ways to respond to heat, rainwater, and other climatic conditions unique to West African communities. Therefore, to get a greater insight on how his architecture adequately adapts to its context, below we analyze some other notable projects according to their use of traditional materials and constructive techniques.
Like many of Kéré’s buildings, this case focused on prioritizing comfort, seeking to create a calm and open library space where students can learn and relax. With that in mind, eucalyptus wood – commonly used in Burkina Faso as a firewood material – was utilized rhythmically in the facade, creating an intermediate shaded space protected from the sun. Also responding to climate conditions, the roof construction integrates a technical innovation: traditional clay pots, handmade by women from the village, were set in the concrete structure to ensure natural illumination and ventilation. In this way, Kéré manages to take advantage of this characteristic cultural object, transforming it into an extremely practical construction element capable of filtering light, generating passive air circulation and creating a beautiful sensory experience.
Modularity and earthy colors
Léo Doctor’s Housing. Léo, Burkina Faso
With the aim of providing a pleasant and secure environment to promote knowledge exchange between medical specialists, this accommodation project follows a modular system. The building is formed by a double-layer wall made of locally-sourced concrete blocks and compressed stabilized earth blocks (CEB). Besides providing structural integrity, the dual layers increase thermal mass, keeping the interiors cool during the day. To protect against degradation associated with weather conditions, a coating of colored plaster covers the exterior walls. Made of CEB, the interior ceiling is designed as a singular vault with the ends left open for daylight and passive ventilation purposes. In addition, a roof of corrugated metal sheeting is placed above the ceiling, protecting the building from excessive heat and, at the same time, sheltering users from rain and sun. Regarding rainfall, the sloped roof directs water into an onsite reservoir, which is then used for irrigation.
Filtered light and cool breeze
SKF-RTL Children Learning Centre. Nyang’oma Kogelo, Kenya
Inspired by nearby residential compounds, the orphanage is organized by a series of clusters surrounding a central courtyard. The outdoor flooring and walls are made of locally sourced laterite stone, which, according to Kéré himself, used to be rejected by the local population by being viewed as “a poor people’s material.” Projects like these, however, served to overcome the stereotype and demonstrate the material’s possibilities with the right construction techniques. After extracting it from the earth, laterite can be easily shaped into deep red bricks, which later harden when left in the sun. With a good capacity to absorb the heavy daytime heat and radiate it at night, the material is an excellent source of thermal mass. Furthermore, each window is designed to respond to various climatic challenges. For example, by including an air vent, fresh air can flow directly towards the inside. Simultaneously, a double-skin roof – composed of a barrel vault with a canopy elevated on steel trusses – allows hot air to escape upwards.
The great advantage of working with local materials and traditional constructive methods is that they are inexpensive, easily accessible and environmentally sustainable. They also stimulate the local economy, strengthen cultural identity and involve skills that are easy to teach, empowering entire communities. And by using these materials in a way that accurately responds to climate conditions, Kéré’s projects are able to ensure comfort, security and high quality architecture, which is key to improve quality of life in underserved areas that previously had no access to electricity or clean drinking water. In this sense, through a deep understanding of the context’s weather and resources, Kére’s buildings are “tied to the ground on which they sit and to the people who sit within them”, as stated by the Pritzker Prize jury.
This article was first published in ArchDaily and is republished with permission.