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

Following the principles of bioclimatic design can greatly improve the performance of a building in sub-Saharan Africa. This is all about using 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. This includes:

  • 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, which has a 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 and published our Details Book. This 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. This helps minimise the cost and impact of transportation. We take into account environmental costs, and as a result 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. This is largely due to the high cement content. It also makes for hot, uncomfortable buildings and has created the need for alternative solutions.

Where possible, we prefer to build with earth. Our preferred choice is Stabilised Soil Bricks (SSB), which 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. Local people help to prepare the earth, process the blocks and stack them to dry. SSBs are then cured in the sun and this eliminates the need for wood to fuel the fire, and as a result helps to curb deforestation. Whilst SSBs are stronger than fired bricks, they 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. As a result 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. They also help to encourage more girls to remain in school as they grow up.

We construct Ventilated Improved Pit latrines. These have a more substantial superstructure and have ventilation pipes at the back. 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 pupils and staff. There is often no reliable source of surface water so this usually requires drilling a borehole. Groundwater is found at a depth of at least 25m, and often much lower. We 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.  Like re-using plastic drinks bottles to build a retaining wall at our Centre for Excellence, as well as to provide lighting in one of the toilet blocks.

Solar lighting has great potential. Where we can we introduce solar lighting in our build projects 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.