Kesho Leo's buildings are a fantastic example of what can be done if people think, talk, and work together, no matter what their backgrounds and skills are. The buildings are also a unique design response to the site, the climate, the needs of the residents, and the resources available.
We won! Kesho Leo wins the National Award for International Architecture.
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fws's building design objectives
From the outset, several design objectives were established that are in keeping with fws's sustainability aims:
- World's best practice
We had to use 'best practice' in all areas of design and engineering, particularly in passive energy principles and techniques.
- Lead by example
The design had to be exemplary and didactic (be able to teach the observer) so that the community - near and far - would see a design that in part or whole, they could adopt and adapt to suit their own needs. The skilled people building the structures would impart their knowledge to those who were unskilled.
The buildings had to be designed in ways to make the best use of the sustainable materials we could afford, and that were readily available. And we would use as much local labour and skill as possible.
a site of sustainable design
The long and narrow building site is just under a hectare (9,500 m2) that slopes away down to a creek at the east end. Our design response was to have series of three buildings: the clinic and manager's residence; the classrooms, kitchen/storerooms and dining area; and the accommodation building - all connected by a central walkway.
We located the buildings to the east and up along the southern boundary, to maximise as much land as possible for agriculture and permaculture with a northern aspect. We also used the slope to our advantage, by slotting in lower-level strong rooms (reused shipping containers) and a wash area, where we located the laundry, showers and compost toilets.
Take a look at the Kesho site layout: kesho-site.pdf
designing for the climate
Our site is in a biome (or ecosystem) unique to a strip of land running centrally across the entire continent called the African 'savanna'. It has the confusing definition of being a wet-dry tropical climate. Basically it's dry for seven months and then rainy for the other five, made up of the 'long rains' and the 'short rains'.
As climate is the major design generator for this project, we used a number of passive energy techniques and design principles for building in the tropics, such as:
- The buildings are raised off the ground to enable passive cooling during the hot seasons and to get out of the mud during the wet season.
- We maximised the length of the north facing facades. Combined with the correct amount of roof overhang, this captures the lower sun angles in the cooler months to enable passive heating while offering protection from the higher sun angles in the hotter months.
- We minimised the lengths of the east and west facing facades, as they take the brunt of the hot morning and afternoon sun making the buildings heat up quickly, especially in the hotter months!
- We designed well-ventilated, long, narrow single-room buildings, especially for sleeping to promote natural flow cross-ventilation.
- A heavily insulated roof was designed to block the intense heat of the sun, and large overhangs shield the walls exposed to the sun.
the 'kanga' roof system
A 'kanga' is a traditional African 'zig-zag' textile pattern that is prominent throughout the region and in an abstract form, it was one of the inspirations for our roof. .
The 'kanga' roof system we developed for this building shows how you can combine a number of different functions into one key element - the building stands out aesthetically as a result of how the system was constructed:
- Prefabrication of elements is something we tried to incorporate where possible, for speed and efficiency. We were able to do it with cast-on-site concrete walkway planks, and with the structural air tubes making up the roof.
- The roofs on all the buildings are bundles of identical triangular long-spanning structural tubes, made up of uncut sheets of plywood to minimise wastage.
- We built these relatively lightweight single tubular elements on the ground, and then lifted them into place (by hand - no cranes here!)
- This 'systems building' approach (used in large commercial buildings around the world) allowed the builders to have one gang constructing the tubes on the ground, while another secured them in place. Not only is it a much quicker way to build, it is more accurate compared to trying to construct them at high level. Importantly, it is a lot safer!
- The tubes, once together side by side, created the folded ceilings of the rooms and the flat platform to fix the roof iron onto.
- The tubes are hollow and open at both ends, and they are also pitched at an angle for drainage so they allow air to move through them, which is a highly efficient form of passive cooling.
rainwater harvesting and solar energy
Off our expansive roofs, we can harvest over 100,000 litres of water which is then stored in a series of 5,000-litre tanks. These tanks are buried under the buildings to keep them cool, and so we don't waste any land for agriculture.
Also on the roof, we have an array of photovoltaic solar panels that generate enough electricity to be able to light our buildings at night as well as provide refrigeration for vital medicines used in the health clinic.
all part of a bigger picture...
Sustainability is what this whole project is all about, and the buildings are only a part of fws's 'big picture'. The buildings link in with all the permaculture systems established across the site, and they are mutually beneficial. For example:
- The composted waste from our toilets and kitchens are totally recycled.
- The grey water from the kitchen, laundry and showers is used for irrigation.
- Methane produced from the biogas generator is the fuel used in the kitchens to cook food.
Find out more about the permaculture systems in place at Kesho Leo.