Sustainable design

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We strive for excellence in our buildings because good enough is just not good enough. We create high-quality buildings that are appropriate for the local community, can withstand the rigours of use and require low maintenance. Sustainability is very much at the heart of our approach.

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BUILDING DESIGN

There is great potential for improving how a building in sub-Saharan Africa performs by following the principles of bioclimatic design which uses natural sources (sun, air, wind, vegetation, water, soil etc) for heating, cooling and lighting buildings.

We incorporate many principles of bioclimatic design into our projects including: aligning the long axis of the building east-west; creating shade by incorporating a 900-mm roof overhang (which is much larger than normal); constructing thick walls from earth-based materials (with high thermal mass); preserving existing trees on the site and planting new trees for shade; increased ventilation provided in the gable walls.

Over the years, we have refined the designs of our buildings. We have published our Details Book which is a detailed construction guide which is used for all our community builds in Zambia.

MATERIALS

Our choice of construction materials is heavily influenced by what is available locally to help minimise transport costs. We take into account both financial and environmental costs, and try to limit the use of high-energy materials such as metal and cement.

Apart from traditional wattle-and-daub, the standard material for construction in southern Africa has become concrete blocks. It is generally accepted that this is unsustainable, largely due to the high cement content, which has created the need for alternative solutions. It also makes for hot, uncomfortable buildings.

We prefer to build with earth and our preferred choice is Stabilised Soil Bricks (SSB) which offers a cost effective, environmentally sound masonry system. SSB can be made on site by compacting earth mixed with a small amount of cement or lime and then compacted by a hand-powered press or a machine. Community involvement is key part of this process with local people helping to prepare the earth, process the blocks and stack them to dry. SSBs are cured in the sun, eliminating the need for fuel wood and helping to curb deforestation. They are stronger than fired bricks but can be more expensive.

Interlocking SSBs were originally used for our projects and worked well, but did not give our trainees enough practical experience of bricklaying so we moved to using plain SSBs. These are laid using mortar as in conventional bricklaying and have a pleasing, uniformed finish which means that walls can be left unplastered.

We have also experimented with rammed earth construction at Shipungu and Katuba Schools. This involves compacting layers of earth within a rigid formwork, which is moved upwards as the layers accumulate. The result is very appealing but although construction is cheap, the building requires high maintenance.

SANITATION

We build latrines at many of our school projects to improve the health and wellbeing of children, and to help encourage more girls to remain in school. We construct Ventilated Improved Pit latrines which have ventilation pipes at the back and a more substantial superstructure. Improved air circulation helps to both reduce smells and prevent the spread of diseases caused by flies, mosquitoes and other insects which are attracted to the pits. The latrines can be emptied and reused.

WATER

At almost all of our community school projects we ensure that clean water is available for all the staff and pupils. This usually requires drilling a borehole because there is no reliable source of surface water and groundwater is found at a depth of at least 25m and often much lower. We then install a hand-pump and construct a concrete apron for drainage.

We use a local contractor to undertake the work and test the quality of the water before commissioning. The water-pump is a community asset maintained by the school or clinic, and if well maintained will last for many years.

INNOVATION: CLEAN AND GREEN

As well as using established methods, we are keen to explore new and innovative ideas and solutions.  We have recently re-used plastic drinks bottles to build a retaining wall at our new training centre and are testing out bottle lights to provide additional lighting in one of the toilet blocks.

Solar lighting has great potential and where we can we introduce solar lighting in our builds to help give communities the opportunity to use their new buildings in the evenings.

To find out more about our approach to sustainable building, materials and design, please get in touch – we would love to talk to you and share ideas.