In 1960 Africa was the least urbanised continent, with an urban population of less than 20% (United Nations Environment Programme, 1999). Urban growth rates of 4.87% led to rapid change and by 2010 over 40 % of the population lived in cities (United Nations Centre for Human Settlement, 2002). Much of this growth has been in the form of informal settlements and in 2012 the UN estimated that 62% of people living in Sub Saharan African cities were living in slums (UN-Habitat, 2014).

Therefore there is any an urgent need to address backlogs resulting from this growth by improving housing and developing more sustainable urban environments.  This generates a range of questions such as:

• How can sustainability be understood in relation to housing in African urban contexts?
• What sustainability objectives should be strived for in this housing?
• What type of indicators can be used to measure the achievement of these objectives?

These questions have been tackled in the Sustainable Building Assessment Tool (SBAT). Table 1 indicates the objective and indicators developed in the SBAT.

Table 1: Sustainable Building Assessment Tool Areas, Objectives and Indicators

Application of the SBAT

The SBAT was applied to evaluate a low-cost pilot housing near Lusaka, Zambia. Housing has been designed by a developer to investigate options before replicating this within a large-scale project. The developer wished to ensure that housing was as sustainable as possible within tight financial constraints. Ideally, the SBAT would have been used to set sustainability targets and inform design and specification decisions during the initial phases of the project. However, in this case, the SBAT was only used to evaluate the house once it had been completed (but not occupied).

Figure 1: Pilot house

SBAT assessment

Findings using the SBAT indicate that the house has a sustainability capability of 2.1. This means the house provides a partial capability for sustainability. The assessment can be summarised in terms of the three performances areas: environmental, economic and social sustainability.

Environmental performance

The house performed poorly in terms of environmental criteria. While the basic building form and envelope openings met energy criteria, other aspects such as building envelope colour, thermal conductivity and energy consuming equipment such as electrical cookers and water heating equipment performed poorly and there was no use of renewable energy systems.

It also performed poorly in terms of water and fittings were inefficient and the building had no capability to recycle water, such as a gray-water system, or to capture this on-site, such as rainwater harvesting systems. Capability for reducing waste and supporting recycling also did not exist and no provision was made for recycling within the house or within the local area.

Performance in terms of materials used in the house was mixed. A locally-made interlocking concrete block was used for the walls. This reduced embodied energy and increased local content. Other materials however generally consisted of imported prefabricated materials and components, some of which contained hazardous materials such as formaldehyde. The building does not support biodiversity as it is located outside an urban area and on a green field site. It, however, benefits from the inclusion of food gardens that surround the house.

Economic performance

An assessment of the location and routes to the house indicates those while that while many facilities such as schools and shops are close by, access to these is difficult and require walking or cycling along busy roads and uneven, narrow paths. Similarly, public transport is available but is in the form of infrequent buses which stop at road location over 800m from the house.

Both the area per occupant of the house and the density of the development within which it is situated do not meet the SBAT criteria. However, some of the space on the site is put to productive use in the form of food gardens. Capability to manage the building and area to support sustainability is low. There are no meters in the building or guidance, such as manuals, on the building’s systems. There is, however, a Residents’ Association and the electricity system has a prepaid meter, which provides some control over consumption.

Other than the building envelope materials, local content of materials and equipment is low and products have generally been imported from China or South Africa. This means that construction of the building provide limited opportunities for local businesses and do not create many jobs within the country. Few measures to support local enterprises and employment have been included in the development however informal capability has been generated by occupants who operate vegetable gardens as well as small poultry, hair dressing and retail enterprises with the area.

Housing is located near a market which provides a wide range of locally produced food, furniture, and other products. Many of the products available, such as locally grown fruit and vegetables, pulses, milk, bread and eggs, support low ecological footprint diets and therefore meet SBAT criteria in this area.

Social performance

While routes (see Economic Performance) such as roads and paths are of poor quality, the house is well located in terms of access to facilities used on an everyday basis, such as schools, sports grounds, food retail, banking, post office, and clinics. Local capability to support health also exists in the form of easy access to fresh healthy affordable food, clean water, clinics and exercise opportunities. The building form and envelope also provide for views, good daylight and ventilation.

Local capability to support education is available in the form of both a primary and a secondary school which is within walking distance (less than 2km) of the house. There is, however, no support for adult or post-school education. Internet access, while available, is expensive. The spatial layout of the house includes provision for studying and homework to be easily carried out.

The building performs poorly in terms of inclusion. It is not located near inclusive public transport and can only be accessed along narrow uneven paths. There are steps into the building and the layout of rooms results in restricted circulation space. Built-in furniture and fittings are difficult to use. Capital and operational costs of the house are also relatively high compared to average incomes making the houses unaffordable for most of the population. No provision has been made to provide more affordable accommodation within the housing area.

There is strong capability for social cohesion with the development. Community halls and sports fields are available a no cost for community activities. A residents’ association exists and are involved in managing the area and initiating local events and activities.

This narrative description of the performance is underpinned by a detailed quantitative analysis using the tool which is used to generate the SBAT report, shown in figure 2. This shows that capability was lowest within the environmental area and was better in the economic and social areas.

Figure 2: SBAT report on housing performance (generated by the tool)

A review the application of the SBAT indicates that it provides a robust way of measuring sustainability performance of housing. Assessment criteria have strong relevance to the achievement of wider global sustainability targets while being appropriate to developing country contexts. Findings and associated recommendations generated through application of the tool also provided useful insight into how sustainability performance can be improved in practical and effective ways.

The full paper on the project is Gibberd, J., 2017. A Critical Evaluation of the Sustainable Building Assessment Tool presented at the West African Built Environment Research Conference,16-18 August 2017, University of Ghana, Accra, Ghana