Timber iQ August - September 2020 // Issue: 50 August - September 2020 | Page 28

WOOD WISE
Timber as the dominant
construction material
for building:
Part 1.
By Stellenbosch University
The question is, can (and should) locally produced wood materials fulfil this
function in residential construction?
Construction contributes to around one third of global
carbon emissions, so the way in which buildings are
built is a really important consideration.
For 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?
HOW WOOD COMPARES
For this research we started by looking at the biggest market for
wood in South Africa currently, which is the roof truss industry. We
looked at two different design houses – a small social house with a
42m 2 footprint and a medium-sized house of 168m 2 .
We then considered the roof truss options that are available: pine,
Biligom and light gauge steel. The team did a lifecycle assessment
for each of these options, which is a very complex process as you
need to evaluate the complete manufacturing process for each
component right down to the source, so for example the source for
steel is mining of metals. The results of this then determine what
the overall impact of each process is that contributes to the
material choice.
THE RESEARCH
The research covered 11 different impact categories and considered
various factors (See Diagram 1)
If you take the impact of the three truss types we found that steel has
a 30% higher impact than the wood options (Biligom or pine) on the
small house. This was a particularly interesting, having the real data
figures, to see this result as many manufacturers market themselves
as green products.
Even more impactful is the medium-size house that shows light
gauge steel has a 500% greater Global warming potential than the
other options. All of the impact categories are equally important
however, in the current environment climate change is a biggest
challenge and considering this major factor in this one building
component. Simply put, if you built a medium-sized house with steel
roof trusses, you would add an additional 6 000kg of CO 2
into the
environment – a significant figure, considering that is only one
building.
RESIDENTIAL BUILDING TRENDS
If we look at residential building activity in South Africa (see Diagram 2)
Diagram 2.
Diagram 1.
from the period 2000 to 2016 you will note that in 2000,
approximately 4 million m 2 of floor area was built, and that increased
to around 9 million m 2 in 2007. This then decreased to around
5 million m 2 in 2016. During this period, we built on average just over
54 000 houses, with the average house size being 114m 2 .
26 AUGUST / SEPTEMBER 2020 // www.timberiq.co.za