I don’t know who invented the tin-roof, but it’s not ideal as the roofing material of choice across Africa. If the outside temperature is 40 degrees it’s likely to be even hotter than that inside a building with a tin roof, because it acts like an oven.
Obviously air conditioning is a luxury most people can’t afford. But some buildings have got to be cooled, and the cheapest, most efficient way to do that is with a feature of traditional middle eastern architecture. The ‘windcatcher’ or ‘shish khan’ in Persian is a tall chimney which sucks the hot air out of the room.
The chimney creates a pressure gradient, allowing less dense hot air to travel upwards and escape into the atmosphere. Even in a windless environment the chimney will force out hot air and pull in cool air due to the laws of thermodynamics. We also build tunnels linking to chambers underground with an opening into a cool, shaded area outside. The cool air is then sucked into the room, as the hot air is pulled out through the chimney. Both designs are brilliant, simple, carbon-neutral, but most importantly affordable solutions which date back to 1300 BC.
We’ve used them in areas like Sudan in pharmacies. In summer indoor temperatures there often exceed 40 degrees. Most drugs just can’t be stored in very hot rooms. But they don’t require frigid conditions either. Using windcatchers and air tunnels we’re able to lower the temperature in a pharmacy by eight or nine degrees. This means pill blisters don’t explode and drugs stay sealed and safe.
Back to basics
These fantastic wind-catchers are being built in the city of Masdar in Abu Dhabi, the world’s first blue-print sustainable city. I like it when a society goes back to its roots and employs traditional designs. They’re sustainable and totally appropriate to the environment.
In Angola in the late 90s I built a 28 room hospital for $7000. The biggest challenge I had on that project was remembering to plant the grass for the roof and wait for it to grow. All the roofs were woven from this dried long grass in the traditional style. It’s still standing today. Most temporary structures in emergencies are built with plastic sheeting for roofing. This isn’t very environmentally friendly but it’s also surprisingly unhygienic. Two layers of plastic sheeting renders your structure weatherproof, but makes a perfect nesting place for mice, rats and snakes.
Build on local knowledge
The great thing about building with local materials is that local people get it. They’re not going to make dangerous mistakes using techniques their grandfathers used or leap-frogging their own development. All over the developing world badly mixed concrete is the cause of accidents and deaths. In a refugee camp on the Congo/Zambia border I learnt how to make bricks using the remains of old termite hills. When they build their mounds, termites filter the soil so it forms a nice sand substitute. You mix cut dried grass or straw with the termite-filtered soil and some water, put it in a cake mould and bake it in the sun for a week or so.
I started a production line. Refugees were just sitting around, so I paid them a small fee to mass-produce the bricks.They were learning a skill, a skill their forefathers had, but got lost along the way. Once these people left the refugee camp they took their skills back to the community. Now their materials will always be on tap. Listening to local people is so important. You can contribute a few small technical improvements, but locals nearly always know best what’s needed.
Mud Bricks are best
When I was in Afghanistan I decided to build a hospital using concrete breeze blocks. But the locals were adamant they wanted it built out of mud. To prove their point they showed me another mud building. Both the east and the west-facing walls had holes in them the size of a tennis ball. They explained that an anti-tank grenade had been aimed at the building, but had entered and exited without going off. Amazing. The mud walls weren’t hard enough to activate the censors on the grenade which are set high for big metal and concrete targets. My breeze block structure would have been a death-trap and the locals knew it.
Solar-powered water purification
Here’s another low-tech gem which could prove to be a game-changer. The problem of purifying water cheaply and sustainably still hasn’t been cracked. But long-term solution might already have been found, it just needs a bit of tweaking. In early ‘80s a scientist called Aftim Acra made a breakthrough called SODIS. He proved you can disinfect water by leaving it for several hours in plastic bottles under the hot sun. The bottles must be Polyethylene Terephthalate, and should be left on a sloped heat-conducting surface like the ubiquitous tin-roof. The sun’s UV rays will destroy the cell structure of bacteria, as long as the water reaches at least 30 degrees centigrade.
The World Health Organization recommends SODIS for use in the home. It’s already been embraced by families all over the developing world. The reason we don’t use it during large-scale humanitarian disasters yet it is that there are a few quite dangerous drawbacks to it. For example your plastic bottles need to be in mint condition, and it’s very hard to work out exactly how long to leave them cooking. Timing depends on the heat of the sun. MSF don’t use SODIS because there’s still no reliable means of testing the water without expensive kits in every home. But the solution to that problem’s being worked on too.
Paul Jawor is a RedR Member and former RedR Trustee. He is a civil engineer working for Medecins Sans Frontières. This article originally appeared online, on the The Engineer.