Sandbag housing construction in South Africa: life cycle assessment and operational energy modelling

Adequate and affordable housing is essential in tackling poverty and improving living and indoor health conditions for lower and medium-income families, in both developed and developing nations. However, there is a lack of affordable housing which directly causes homelessness and formation of slum-dwellings. Sub-Saharan Africa has the most urban slum dwellers with an estimated 53.6% of the urban population in sub-Saharan Africa dwelling in urban slums. Additionally, the housing deficit in South Africa currently stands at about 2.2 million units, with a projected housing demand of 500,000 housing units over 20 years. Given the climate crisis and need for affordable housing in South Africa, low-cost and low-carbon solutions are essential. Sandbag building technology (SBT) is one such promising solution, consuming less energy during construction and operation than conventional technologies as well as regulating the internal temperature of the building through thermal mass. However, there is still a need to assess how this simpler construction style and locally sourced building materials perform from a whole life cycle perspective. Thus, this paper presents a life cycle assessment (LCA) determining the holistic sustainability of a vernacular, sandbag house design in South Africa.

The environmental LCA analysed the SBT under two scenarios: manual and automated, based on extraction of sand. The life cycle cost (LCC) analysis evaluated the SBT house from the different life cycle stages: design, production and operation, and disposal. The findings show that the carbon dioxide equivalent (CO₂e) emissions depend largely on the availability of locally sourced sand and whether the process is manual, automated, or both.

Upfront embodied CO₂e emissions total 189 and 174 kgCO₂e/m² for the automated and manual scenarios, respectively. Assuming no decarbonisation, the operational emissions equal 7966 kgCO₂e/m², but could be as low as 1444 kgCO₂e/m² (achieving net zero by 2050). Whole life embodied CO₂e impacts, i.e. stages A and C, total 262 and 247 kgCO₂e/m² for the automated and manual scenarios, respectively. The difference between the manual and automated scenarios can be significant at 15 kgCO₂e/m², equating to an additional 1125 kgCO₂e for a 75m² house. The estimated LCC for a 75 m² building constructed with SBT is R 533,898.01 (US $31,167) or R 7118/m².

The sandbag method remains challenging for multi-storey construction due to the weight; however, it can contribute to low carbon, affordable housing in South Africa as a sandbag house does not need highly skilled labour or expensive materials.