Timber as the dominant construction material for building: Part 2

By | 2020-10-29T11:57:14+00:00 October 29th, 2020|

By Stellenbosch University (Presented at the Wood Conference 2020)

Can timber resources compete on a 100% timber-build housing market share?

Also read: Timber as the dominant construction material for building: Part 1.

Construction contributes to around one third of global carbon emissions, so the way in which buildings are built is a really important consideration.

As a recap into our research into this subject: We posed three basic questions we wanted to answer:

  • How does wood compare to competitive building materials in terms of environmental sustainability (in a South African context)?
  • What will the environmental impact be if we become a ‘wood building’ country?
  • Can we sustain a dominant residential wood building sector with local forest resources and services?

Part 2 of this study looks at potential resources for wood housing in South Africa, and the South African transport impact on Global Warming Potential (GWP). Please see Part 1 published in the previous issue of Timber iQ.

Sustainability aspects with local materials

Considering our timber resources and by-products of the industry our research looked at some of the most obvious sources of materials (see Diagram 5). One being the export of significant amounts of wood chips to Asia for pulp and paper factories.

Wood chips are a very low-value product currently, so this resource has the potential to be upscaled to a high value product, like housing. We can determine how much wood chips would be needed to build a typical timber-framed house and the result is
47 531 houses (of an average size of 114m2). Considering our estimated housing requirement of 54 000, this resource alone would be a sustainable source.*

The second resource that is highly feasible is afforestation, such as in the Eastern Cape where the Government has identified 140 000 hectares of land for this purpose. Once this solution is in full production it can sustain approximately 37 000 houses per year. Within as few as eight years a project such as this could already start producing the timber required. Other studies show that dryland afforestation in the Western Cape is another potential source. As you can see, we have more than enough resources to compete on a 100% timber-build housing market share, which for us was quite a surprise. Essentially there is no excuse not to build with wood.

Importing and transportation – important factors

Different transport modes have very different environmental impacts. If you look at truck transportation, this method has a 9-times higher GWP impact per tonne moved than container shipping, and then dry bulk shipping is approximately half of that (see Diagram 6).

The bottom line with transportation is your shipping distances are constant and so you can’t do a lot around that, however you should minimise truck transportation distances. As a comparative example, if you import logs from Mozambique to Cape Town by truck and compare this to importing products from Brazil via shipping, research shows that it would be better importing via shipping rather than the truck option when calculating this factor in GWP of the product.

Conclusion

Research has shown that the environmental impact of wood roof trusses is far lower than light steel, even though manufacturers claim being a comparative green option. South Africa has the forest resources and products, so there is no excuse not to choose timber buildings as a dominant material in construction, and by having a larger wood-building market share there is significant reduction in global warming potential. Finally, the global warming impact of importing wood-based materials or products currently not available in South Africa can be minimised by intelligent purchasing decisions.

Should further information on this research be required, you are welcome to contact Stellenbosch University directly. This article is published as a presentation from the 10th Wood Conference held in Cape Town at the end of February 2020.

*Note: there are of course challenges with this scenario because it is not easy to use eucalyptus and acacia wood for some of the products, where for others it wouldn’t be a problem. Many hours are being spent at the university at the moment, where the focus is on such solutions.