(CNN) Millions of households in the Sahel region of West Africa live under a growing threat.
Deforestation and climate change have decimated the available supply of wood that is used for traditional roof construction, forcing many to use imported sheet metal.
This is both prohibitively expensive and unsuited to the climate, entrenching poverty and making homes that boil in summer and freeze in winter.
One creative enterprise is reaching back over 3,000 years for a solution, borrowing an architectural technique from the ancient Nubian civilization of latter-day Sudan to offer superior homes at minimal cost.
The NGO La Voute Nubienne (Nubian Vault) is training an army of masons to build homes from the earth, and the ancient innovation is having a profound impact.
The Nubian technique uses bricks and mortar produced from local earth, laid over a foundation of rocks. A home can be produced in 15 days, and the method is versatile enough to produce a range of buildings from mosques to farmhouses.
La Voute Nubienne is working in five West African countries; Burkina Faso, Mali, Senegal, Benin and Ghana, where around 20,000 people now live in the Nubian homes.
"We have proved our concept is viable and works for the population," says Thomas Granier, a French builder who co-founded the NGO with Burkinabe partner Séri Youlou. "There are half a billion Africans living under corrugated iron roofing and our target is to provide a strong alternative."
The earth homes offer more than expediency, as they are well adapted to the local climate.
"Nubian Vault buildings provide excellent thermal insulation, making the buildings cool during the day and warm during the night," says Nick Nuttall, spokesperson for the United Nations Framework Convention on Climate Change (UNFCCC).
La Voute Nubienne believe that long term success depends on building a sustainable market, as expressed in their motto: "A roof, a skill, a market."
The NGO has trained over 500 masons, according to Granier. This new workforce can respond to increasing demand, as well as training a new generation to sustain the practice.
One-third of the new construction market is now fully autonomous, and the proportion is rising.
"When we have deployed enough capacity this won't belong to us, it will belong to the community," says Granier. "The target is push this alternative until we don't have to and it pushes itself."
The market model does not make the homes unaffordable. Granier estimates the cost of a basic building at $150, although in many cases the owner will supply some of their own labor, or barter goods for part of the mason's fee.
But despite the informal nature of the industry it is making significant contributions to the local economies, valued at over $2 million by the NGO, and this figure is set to rise.
La Voute Nubienne is now aiming to build the workforce and dramatically scale up construction.
The fledgling industry currently enjoys growth of around 30% each year, says Grenier, and he wants to reach 50%.
"With 20 points more we could house one million people by 2030," he says. "If we do that we can have a real macro impact on local economies and habitation standards."
The NGO is intensively lobbying potential government and development partners to drive the business forward and reach new markets -- and new countries. With steady growth the industry could generate over $70 million by 2030, the group projects.
Such growth could also have significant benefits for the climate, potentially slowing the deterioration that has threatened so many homes.
"Nubian Vault uses only locally available materials with a very low carbon footprint," says Nuttall of the UNFCCC. "As no wood or straw is required in this building technique, the project helps reduce deforestation. None of the buildings need to be manufactured or transported long distance, which means it also saves a lot of CO2."
With low costs, economic boosts and climate gains, the ancient Nubian technique appears built to last.