The small town of Dandaji, Niger, sits on the edge of the Sahara Desert. It is a place where temperatures routinely top 45C, blanketing residents in a suffocating, oven-like heat.
Unless theyre in the towns mosque.
With its tree-filled garden, soaring ceilings and earthen-brick walls, the building has been designed to chill itself. On the hottest days, it can be up to 15C cooler than the outside air without air-conditioning.
The mosque is one of two buildings the other is a library that make up the Hikma Community Centre.
While it was completed in 2018, the award-winning complex co-designed by Nigerien architect Mariam Issoufou is receiving renewed attention as urban areas swelter under record-breaking temperatures.
Whether youre in Niamey or New York, climate change is fast making extreme heat the new normal, says Hongpeng Lei, the Chief of the Climate Mitigation Branch of the United Nations Environment Programme (UNEP). We need to develop better ways of building if we want our homes and offices to be livable in the years to come.
The Hikma complex is a marvel of what experts call passive cooling a smorgasbord of architectural techniques that ease indoor temperatures without the need for air-conditioning.
A prime example of this are the mosques walls. Aside from a few concrete ribs, they are built entirely from earthen bricks, which draw inspiration from Nigers adobe buildings of yore. The bricks are forged by mixing small amounts of cement and water with laterite, a rusty-red soil found across West Africa. More porous than concrete West Africas building material of choice the bricks allow heat to dissipate at night, keeping temperatures comfortable.
Since the Hikma complex was completed in 2018, a growing number of West African buildings have used compressed earth bricks, in part because of its influence. That represents a mini-renaissance for a substance once viewed as backward, says Issoufou, who created the complex alongside Iranian architect Yasaman Esmaili.
Since the beginning of the 20th century, concrete has been seen as the material of progress. I was laughed out of rooms when I brought up earth, she says. But there is a lot of wisdom embedded in the buildings of the past.
Another key to the mosques cooling is its vaulted ceilings, which range from six to nine metres high. Their loftiness allows hot air to waft up and away from worshippers. Once it reaches the mosques roof a series of earthen brick rings crafted by local masons it dissipates into the outside air.
The mosque also has precisely aligned doors and windows that allow breeze to pass through when opened. Equally important, the mosque is not one cavernous space. It is split into two sections, or volumes, each with their own doors and windows that face each other.
To keep cool, the mosque has one more trick up its sleeve. Just outside is a tree-filled garden fed by a drip irrigation system, which captures water during Nigers brief rainy season and stores it in a cistern.
The trees visible in satellite images serve two purposes. First, they provide a dose of cooling shade. Second, when the water in their leaves evaporates a process known as transpiration it chills the surrounding air.
We underuse nature, says Issoufou, who was named a 2025 UNEP Champion of the Earth, the United Nations highest environmental honour. Its incredibly versatile.
Around the world, there is a growing push for architects and city planners to embrace passive cooling strategies, which can lower indoor temperatures by up to 8C, according to a recent report from UNEP.
Along with keeping congregants cool, there is another big benefit to the way Dandajis mosque was built: it has a tiny environmental footprint.
Since the laterite soil in its bricks was sourced locally, builders didnt need to import huge amounts of concrete from afar, which can drive up greenhouse gas emissions. At the same time, the bricks used far less cement than concrete would have. Cement production is a major source of emissions, as is air conditioning, which the building forgoes. (On the hottest days, mosque officials bring out a few oversized fans.)
Many see the complex as an antidote to the resource-heavy construction practices that dominate in most places. Glass, steel, concrete, air-conditioning these things take energy to manufacture and maintain. In fact, the construction and operation of the worlds buildings consume nearly 50 per cent of raw materials and produce more than one-third of all greenhouse gas emissions, finds UNEPs new Global Status Report for Buildings and Construction.
Support for more eco-friendly building practices is growing. UNEP, for instance, is working with countries to expand the use of low-carbon and locally sourced materials. In Ghana, it is helping develop affordable, climate-resilient housing, while in Senegal it is backing the production of insulation boards made from typha, a fast-growing local plant. The effort also focuses on training local builders and businesses in techniques like circular construction and climate-sensitive design.
While materials like laterite bricks are very specific to West Africa, most countries have their own equivalents, Issoufou says. She points to places like Europe and North America, where cross-laminated timber made by gluing together wooden planks is emerging as a low-carbon alternative to concrete and steel. In parts of Asia, bamboo one of the worlds fastest growing plants is experiencing a revival because it is strong, sustainable and cheap.
With the planet slipping into an ever-deeper climate crisis, building edifices that are sustainable and that cool themselves is the rational thing to do, Issoufou says. The question is: why would you not do that?
About World Environment Day
World Environment Day, celebrated annually on 5 June, is one of the planet's largest platforms for environmental outreach and is led by the United Nations Environment Programme (UNEP). This year's iteration, hosted by Azerbaijan, will focus on the mushrooming climate crisis. See how you can get involved.
Written by: Andrew Raven
Reviewed by: Hanane Hafraoui, Gulnara Roll, Hongpeng Lei
