3. Sustainable Materials
Material choices are often driven by cost and fashion, which can result in unsustainable and climate inappropriate buildings. The ubiquitous metal sheet roofing for instance, seen on rural and urban buildings across East Africa, contains huge amounts of embodied energy and creates acoustic and overheating issues for users.
Designers should look to enhance the comfort and health of building users and identify unique opportunities for training and job creation through material choices. materials should be selected for their environmental credentials - low embodied energy and the ability to enhance local ecosystems or sequester carbon through their production. The ultimate goal should be to design and construct buildings that generate at least as much energy as they use and have a positive net effect on the local ecosystem.
How buildings are made can have a significant effect on local ecosystems as well as contributing to the global crises of climate change and biodiversity loss.
The stress that we are placing in the global environment comes from three sources. Firstly we are extracting materials from beneath the earth and releasing stored carbon into the atmosphere. Secondly the organic chemical processes that are now part of our world - from the production of plastics to persistent pesticides - are overloading natural systems with materials that do not break down in nature. Thirdly we are dramatically changing the world’s natural ecosystems and causing species extinction at an unprecedented rate. All materials used in construction need to be evaluated against these criteria.
The energy used to construct the built environment in East Africa is one of the region's major contributions to global warming.
In much of the world the amount of ‘operational’ energy we use in our buildings, and therefore the carbon dioxide emissions from them, is a much greater issue than the amount of energy that goes into constructing them. In the relatively benign climate of East Africa this is not the case: the ‘embodied energy’ that goes into construction is more significant. The manufacture of cement makes it the most carbon intensive building material but the firing of bricks is also highly problematic, particularly if it also results in irreplaceable tree loss. By contrast timber from sustainably managed sources is a way of embedding CO2 in construction.
Ilima Primary has virtually no embodied energy - built entirely with simple hand tools and local materials
Using Local Materials
Use local materials and local labour, both to avoid the energy cost of transportation and to support the local economy.
Local materials are often scarce resources and when translated into building materials it is important to consider whether their loss is a problem, or whether they can easily be replaced. Soil from the site is the most basic sustainable material to build with, followed by materials that are grown, such as timber or bamboo, but only providing they are part of a managed ecosystem. Providing resources are extracted responsibly, sourcing materials from on or around the project site can have numerous benefits.
Ilima Primary 99% of materials were sourced from within 10km of the project site
Adapt a 'cradle to cradle' philosophy and build with materials that are recycled or recyclable in order to avoid wastage of both materials and energy.
Traditionally architectural materials were repaired and reused until they effectively decomposed, the timber rotted, or the bricks turned back to earth. A newer more resilient generation of building materials like concrete is much more difficult to recycle, particularly if it is mixed with steel reinforcement. The use of plastic materials with a limited life is becoming a major problem globally and we need to look at reducing production, creating ingenious reuse and opening up recycling pathways, rather than turning buildings into waste.
This guide looks primarily at the structure, materials and environmental design of low-cost single storey rural school buildings.
Building typology is a significant driver for structural systems and materiality. Simple single storey buildings with loadbearing walls are likely to be dominant typology for schools in East Africa for the next decade or two. As urbanisation increases and land becomes scarcer the need for two and three storey school buildings will begin to emerge, particularly in areas of higher density. Those buildings are likely to be reliant on in-situ concrete or steel as a way of providing safe, fire resistant and earthquake proof construction.