The green house in sub-Saharan Africa

Climate challenges are leading to a reconsideration of our consumption and production patterns. We are seeing the emergence of initiatives in favor of protecting the planet, ranging from the global sustainable development goals to those of the Paris Agreement. Everyone is getting involved and trying to move from talk to practice. Concepts accompanied by the adjective "green" by analogy with nature, are emerging. Here, everything becomes "green", even companies, because it is necessary to preserve the planet for future generations.

The building sector does not escape it. Green houses are springing up like mushrooms, including in sub-Saharan Africa, even though this type of construction is not new. Very often perceived as a sign of poverty, these houses made of local materials integrate several environmental assets that contribute to better preserve the planet. This article presents some prototypes of African ecological houses.

The Nubian vault

From present-day Upper Egypt, the Nubian vault is a form of construction that is both ancestral and innovative, which seems to be a solution to the various current and future challenges that Africa is experiencing namely: galloping demography, global warming, desertification, the housing problem... the answer to these challenges lies in the fact that it is an architectural know-how accessible to all social strata, elaborated on natural materials.

These materials are essentially composed of earth brick made of water and banco, that is, a kind of adobe that is obtained by mixing earth, straw and pebbles. In addition to this, it is necessary to obtain a plastic tarpaulin used to insulate the roof, and a coating generally consisting of shea water, a tiny amount of tar and sand.

This ancestral technique makes it possible to build homes with vaulted roofs without formwork. It is perfectly adapted to the climatic variations of the Sahel countries, characterized by a high degree of rainfall and intense heat. Its particularity is based on a lesser waterproofing against rain and a regulation of the temperature during the hot weather. This is all the more true as this fact is approved by a mason of a Franco-Burkinabé association that has set itself the goal of restoring the image of this ancient construction when he states:

"When it's cold outside, it's nice inside and you don't hear the noise."

This assertion implies that staying in a house made with a Nubian vault would give the impression of being nice and warm in a cocoon. In addition to that, one would not be bothered by heat or humidity depending on the season. Thus, this type of house seems to be less energy consuming because one does not need to bother with air conditioning to fight against the extreme heat.

In this case, we are talking about a green house that not only is not expensive during its construction, but also after this stage. The presence of local materials that can be easily found near the construction sites is a boon, in terms of reducing greenhouse gases produced in case they would have been transported. Also, this structure allows to make huge savings because we do not use expensive materials such as wood, and sheets.

The Nubian vault houses apart from these multiple advantages mentioned above, are breathtakingly beautiful. They give the possibility of having roof terraces. They can be found in the countryside as well as in the posh districts of the capital of Burkina Faso for example; but like any construction, there are problems to be raised such as the construction of houses on floodable grounds or a bad drainage of surface water. So, particular attention should be paid to these two aspects. That said, the Nubian vault is not the only form of ecological house that can be observed in Africa.

The mud brick house and the poto-poto (cob) house

Just like the Nubian vault house, the compressed mud brick house and the poto-poto are traditional constructions with the same properties in terms of temperature regulation, limitation of expenditure; the only difference is that in this framework, the construction technique is not the same.

As for the compressed earth brick construction, its shaping depends on the owner's purse. It may happen that the brick is made by hand or with the help of machines. In the first case, the most impressive, after having a large quantity of earth, the bricks can finally be formed. They are mainly composed of clay and sandy soil, carefully mixed by a craftsman who uses a spade and water to form a homogeneous paste ready to be used to make bricks. Then, they will be dried in the sun and then fired. The main difference with the Nubian vault is that here we need wood to serve as formwork and metal sheets. But the construction is still environmentally friendly and less expensive, because it needs only a small amount of wood.

In addition, the price of the mud brick remains lower. This is precisely what Anaïne Tchadféké, owner of Chadian nationality of a house made of mud bricks reports that he disbursed three times less by building his home with mud bricks i.e. he spent 500,000 CFA francs instead of 900,000 CFA francs in case he would opt for cement.

Very close to the mud brick house, the poto-poto him, even if it is made with earthen adobe, does not require brick. According to Djatcheu, the walls are made with a "framework of vertical wooden stakes and horizontal bamboo attached to the stakes, onto which balls of earth mixed with water are thrown by hand. Here, the structure is less solid than the previous one. However, it keeps its originality and its ecological side. This style of house is found in the countryside of sub-Saharan African countries such as Senegal and Cameroon. The poto-poto is a precarious, spontaneous house. It is practical for insulation, but does not resist to bad weather and humidity. For this reason, it is often covered with plaster later.

These seemingly archaic houses appear to be solutions to the problem of climate change and even to the fight against poverty. But for this to have an effect, there needs to be awareness on the part of the new generation, training and funding to perpetuate African traditions and at the same time preserve nature.

Illustration: The Nubian Vault - Photo Gallery - Rural Nubian Vault in Danou

References

Association la Voûte Nubienne (AVN), "Building differently in Africa"
https://www.lavoutenubienne.org/-le-concept-technique-

Association "la Voûte Nubienne," 2016, "VN pathology, disorders and disasters"
https://www.lavoutenubienne.org/IMG/pdf/16-07-16_pathologies-desordres-sinistres-vn_mh_v1.2.pdf

- Paquin Marc, Rinaudo Cécilia, "The Nubian vault, a habitat that contributes to the energy transition"
https://www.mediaterre.org/docactu,TWVkaWF0ZXJyZV9Bcm1pbmVzL2RvY3MvcGFnZXMtZGUtNzMxbGVmLTEwOC0wMDU=,1.pdf

- POUFFARY Stéphane, DELABOULAYE Guillaume, WATERKEYN Philippine, "Sustainable building in Africa: issues, challenges and realities"
https://www.mediaterre.org/actu,20150525155743,11.html

- Servane Philippe, Dobret Anaïs, 2017, "Nubian vaults: the new life of an ancestral building technique"https://reporterre.net/Les-voutes-nubiennes-la-nouvelle-vie-d-une-technique-de-construction-ancestrale