The back of one of the Teacher’s Houses at Shilanona
One of the biggest obstacles to student achievement in Tanzania is the lack of teachers. The average student-teacher ratio is 54:1. In rural districts, it is usually much worse, especially at the primary school level. It’s not uncommon to find a classroom full of eager students with no teacher. There are many reasons for this—too few teachers for the number of students and low pay among them—but poor-quality or non-existant housing is a key factor in rural areas.
Shilanona Primary School, with 11 teachers for 586 students, is a clear example of these issues. The campus is set about a kilometer from the small village of Shilanona, on a handsome hilltop site. There are three 40-year-old teacher houses set behind the classroom buildings, poorly constructed and poorly maintained. Three more houses were started in 2006, but only two were completed enough to allow occupation. This spring, a storeroom in a classroom building was converted to living quarters for two teachers, with a thatched wall for minimal privacy. The rest of the teachers must bicycle about 10 kilometers each way in heat and torrential downpours from the district center at Ngudu.
Initially, Africa Schoolhouse had planned to renovate the three oldest houses as part of its campus renovations. However, after examining the poor condition of the buildings, we all agreed that the funds would be better spent building two new houses, thus increasing the overall capacity on the site.
This provided an unexpected opportunity to improve the Africa Schoolhouse housing prototype. Teacher’s housing had first been created by Leslie Jill Hanson for the Ntulya Primary School. Three houses at the Ntulya Health Outpost were built in 2011, following designs developed by the University of Florida School of Architecture. As our homebase and living laboratory, this became a starting point for the design.
We had several design goals. First, to fit the buildings more comfortably into the landscape of rural central Tanzania. Second, to minimize the impact of the intense sunlight and heat. And finally, to create a prototype for Milembe School and other future Africa Schoolhouse projects, one that could be built in a variety of site conditions, with their crews and local, sustainable materials.
Traditional Sukuma houses
Nurses Housing and Volunteer House at Ntulya
Before developing a solution, we became more familiar with the landscape, the climate and the materials. We spent February exploring the region around Mwanza and as far north as Butiama, visiting school sites and observing the villages and countryside. Everywhere, we saw the soft lines of the traditional mud brick or reed and mud (wattle-and-daub) buildings with their thatch roofs—used by the Sukuma people as well as other tribes in the region. They seem to blend into the scrubby, boulder-strewn landscape far better than the newer brick houses with crisp corrugated metal roofs that are rapidly replacing them.
At the equator, with the sun transiting high overhead all day and all year round, those metal roofs also get maximum exposure to the sun, capturing its energy all day long. With no interior insulation, that heat radiates the heat into the space below. Soon after arriving, we purchased a thamometa in Mwanza and began taking hourly readings of the temperatures both outside and inside the Volunteer House. By late morning, the outside temperature was in the low-to-mid 90’s. Inside, it was close to 100 degrees Fahrenheit and the underside of the green metal roof reached over 115 degrees.
Whenever we looked up at the underside of the roof panels, we could actually feel the heat radiating down on our faces. It was like standing in front of a cast iron radiator on a Maine day in January, with the furnace blasting away. Keeping the doors open for breezes helped a bit, but that let in squadrons of annoying flies, too. Not surprisingly, dissipating the unwanted energy and keeping it out of the living space became a key objective.
Scott had first become familiar with the concept of double roofs for cooling when he bought a 1975 Land Rover with a “Safari” roof. Double roofs are constructed in Maine to insulate from the cold, and they are becoming a more common practice for passive cooling in tropical areas as well. A number of stunning and sustainable designs have been recognized through awards from the Holcim Foundation, including the Secondary school in Ouagadougou, Burkina Faso by Francis Kere Architecture and a Health Center in Dharmapuri, Tamilnadu, India by Flying Elephant Studios.
New Teachers House with “Sukuma Form” roof
Floating a segmented second roof above the basic gable form on wood trusses satisfied two objectives—fitting into the landscape and making the interior cooler. It also incorporated the same low-tech materials—corrugated roofing and wood trusses—currently employed by Africa Schoolhouse crews. The second roof adds to the cost (about $2000 per house, for a total cost of $9500), but we hope that the greater comfort will make the new housing more desirable, potentially attracting more teachers to the school. This could also ensure that the future Milembe School teachers are among the best.
Cross-section of roof, showing conventional truss and roof below, and spacer trusses above
The new compact, 550-square-foot floor plan offers a number of other features as well:
- covered outdoor veranda along the front of the building;
- open living/dining space connected adjoining the veranda;
- three bedrooms, for parents, boys and girls, or several unmarried teachers living together;
- one bedroom defined by a disengaged diagonal wall that would allow it to be used as a study;
- covered outdoor kitchen to the rear, providing good venting for the typical wood fires and replacing the typical practice of cooking in the yard or in an unvented lean-to;
- a duplex composting latrine and shower building, constructed between every pair of homes; and
- rainwater harvesting in a elevated storage container located in the kitchen area.
Building materials consist of: site-harvested stone and concrete foundations; concrete slab; walls of fired jumbo brick burned nearby; wood trusses and purlins with galvanized corrugated steel roofing panels. Open bond front and rear wall areas under the porch roofs will provide generous cross- ventilation. Windows are jalousie-type, allowing for post-installation glass-fitting, with site-fabricated wood doors, frames and trim.
We knew that construction of the two new houses would not have advanced beyond the foundations when we left Tanzania in early April. Therefore, Scott worked with the crew to construct several mock-ups, the most important being a one-bay trial of the “Sukuma Roof.” It was built on top of the existing roof for Classrooms 5-8, which is planned for replacement in the next phase—and may also be a good candidate for a double roof. Once the materials were at the site, carpenter Mapanbano and Scott constructed the trusses in one day. Mapanbano and his crew installed the trusses the next day and the roofing on the third day.
Building the trusses
Setting them in place
The completed mock-up on Classroom 5
Mapanbano and Kishosha reviewing Scott’s ridge vent mockup on the front porch of the Volunteer House
The exercise allowed the crew to see how the double roof, though a new form, incorporated the same details and materials used in earlier projects. They offered valuable input on the construction and sequencing, which led to the refinement of many details. One was a vent strip at the ridge that should allow hot air to escape from the interior spaces and the roof cavity, while rejecting water and foiling flying critters. Another was a relatively simple way to waterproof the nail holes in the roof.
Both features had gained personal importance after nights listening to the bats roosting in the trusses of the Volunteer House, and days arranging buckets and moving furniture once rainy season began in earnest. This convinced us that mock-ups should be a critical part of future construction projects—as well as the importance of living in a place as a precursor to design. If the contingency allows one or two double roofs to be constructed at Shilanona, it will also give us a real-life, real-time model, where we hope to track the cooling with our “thamometa” on the next visit to Tanzania.
For more on the educational system in Tanzania: http://en.wikipedia.org/w/index.php?title=Education_in_Tanzania&printable=yes
For more on the Holcim Awards: http://www.holcimfoundation.org/T154/holcim_awards.html
For details of the Secondary School in Burkina Faso: http://www10.aeccafe.com/blogs/arch-showcase/2012/04/11/secondary-school-in-gando-with-passive-ventilation-system-in-ouagadougou-burkina-faso-by-francis-kere-architecture/?interstitial_displayed=Yes
For images of the Healthcare Center in Dharmapuri, Tamilnadu, India: http://www.flyingelephant.in/complete.php?pid=6