Abstract

 
 
 South Africa was the first country in Africa to implement a locally developed green building rating tool and has a growing number of rated green building projects. The method of life-cycle assessment can help to compare and assess the environmental performance of building products. At present, more than 70% of all sawn timber in South Africa is used in buildings, mainly in roof structures. Light gauge steel trusses have recently also been gaining market share. However, to date, no studies have been conducted that quantify and compare the environmental impacts of the different roof truss systems in South Africa. We thus compared several roof truss systems (South African pine, Biligom and light gauge steel) found in low- and medium-income house designs in South Africa using a simplified life-cycle assessment approach. Our results show that the two timber systems had overall the lowest environmental impact. Although the difference between the timber systems was small, light gauge steel had a 40% higher normalised impact over all assessed environmental impact categories. The benefit of biogenic carbon dioxide present in timber proved to play a significant positive role in the global warming potential impact and could even be further reduced if wood were used to generate energy at its end-of-life. This study demonstrates the potential advantage of using local timber products to reduce the environmental impact of the truss and building industry in South Africa.
 
 
 
 
 Significance: 
 
 
 
 Timber truss systems showed overall lower environmental impact than light gauge steel trusses, with implications for green building.
 
 
 
Highlights
We investigated and compared the potential environmental impact of different roof truss systems typically found in low- and medium-income house designs in South Africa using a simplified life-cycle assessment (LCA) approach
We present the potential environmental impact of the modelled products and discuss adjustments and assumptions made with regard to the availability of South Africa specific life-cycle inventory (LCI) data and validity of obtained results
For the smaller truss system, light gauge steel (LGS) had about twice the global warming potential (GWP) impact of the timber systems and the normalised impact over all environmental indicators was about 40% higher
Summary
Numerous studies have shown that substituting steel, concrete and brick materials with renewable and sustainable wood products can significantly lower the environmental impact of a building over its lifetime.[4,5,6,7,8,9]. Residential roof truss construction in South Africa is the single biggest user of locally produced structural timber. Light gauge steel (LGS) construction as well as LGS roof truss systems have gained a noticeable market share and offer another option as roof truss material. With steel prices currently low, many building projects and smaller roof spans with steel have become economically viable options in South Africa, and in many cases replaced wood as the preferred truss material.[12,13]
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