Latest CBA Newsletter - Concrete Block Association

environment & sustainability
Is timber the most sustainable
form of construction?
This article is based on a briefing paper
from our colleaguues at MPA Concrete
Centre. It is full of facts and qualified
references to give you the members,
the ammunition to combatany misleading
claims made for the sustainability of timber
framed buildings.
Timber is not the most sustainable form
of construction. No material can claim
to provide the most sustainable form of
construction as it depends on a range of
project specific factors and requirements,
and against what criteria you are judging.
The issues are complex and need to
be addressed on a case-by-case basis
considering the whole life cycle of the
building.
Sustainability benefits
The two main sustainability claims made
for timber are low ECO2 and that it is a
renewable resource. All other sustainability
benefits are at least matched or exceeded
by concrete and masonry solutions (e.g.
low waste, energy efficiency; long life;
recyclable; responsibly sourced; whole
life performance, thermal performance).
Rob Pannell, the head of Zero Carbon
Hub has recently stated that he has no
views either way on embodied carbon
timber vs masonry.
1. Concrete has low ECO 2
Masonry and concrete buildings have a
similar level of ECO 2
(emodied CO 2
) to
timber buildings and in terms of kg CO 2
/t,
concrete is lower i.e. the timber used in
housing is around 690 kg CO 2
/t (TRADA
data), whilst ready-mix concrete is about
103 -162 kg CO 2
/t, precast concrete
around 180 kg CO 2
/t and concrete blocks
are about 75-240 kg CO 2
/t.
The above is verified by independent
reports: e.g. NHBC report on housing
stated there was no significant difference
between timber frame and masonry. Ref:
Operational and embodied-carbon in
new build housing. A reappraisal - NHBC
Foundation Nov 2011:
a. Some timber has higher (by up to x10
times) ECO 2
than some concrete e.g. CLT,
Glulam
b. Using recognised public data published
by the timber industry their claims for
negative carbon appear incorrect. This
discrepancy comes from the use of
selective choice of life cycle stages by the
timber Industry which ignores end of life
scenarios.
c. The notion of sequestered carbon is not
widely recognised by LCA criteria as the
phenomenon is only temporary and the
footprint is dependent upon the end of
life scenario (methane from decomposition
or CO 2
from combustion). Refer to the
EEB Guide (Energy Efficient Buildings
http://www.eebguide.eu/) “Operational
Guidance for LCA Studies of the Energy
Efficient Buildings Initiative”
2. Plentiful local resource
A focus on renewable resources which can
only be met by bio-products is flawed as
a basis for the UK economy due to land
availability and other issues.
a. Construction grade timber is not
generally available in the UK and is
therefore imported from Europe and North
America
b. But the UK has plentiful natural resource
for concrete (1000s of years potentially)
c. Reliance on grown product is many
years away and could have a significant,
detrimental impact on UK environment
14 www.cba-blocks.org.uk