Durability and Environmental profile of UK Grown Western Red Cedar
Date: Wednesday, March 17 @ 01:26:04 MST
Topic: Timber
Durability and Environmental Profile of UK Grown Western Red Cedar
By Dr Terry Mabbett
Western Red Cedar (Thuja plicata), a native of the Pacific North Western region of North America, grows mainly in coastal forests, but also in the drier interior forests of Washington, Idaho and Montana and British Colombia in Canada.
Trees are highly valued for timber that is used in a wide variety of applications such as cladding, shingles, doors, windows, railings, posts and beams, as well as interior décor including furniture. Excellent durability is afforded by natural oils that act as preservatives to help the wood resist insect invasion and fungal decay. Less chemical preservatives are therefore required, compared with other timbers, giving Western Red Cedar a good environmental profile.
Western Red Cedar is also a dimensionally stable wood that lies flat and stays straight. Properly finished and maintained, the wood ages gracefully and endures for many years. If intended for applications in contact with the ground, it should then be treated with preservative.
Harvests of Western Red Cedar from ?old growth? forests are increasingly limited due to increasing awareness of their conservation value as primary forests. There are extensive plantations in North America and the species has been grown in the United Kingdom for about 100 years. But concerns persist that intensively grown and produced Western Red Cedar is not as durable as that from ?old growth? forests.
Joanne Roberts, postgraduate student on the MSc Course in Forest Protection and Conservation at Imperial College London (Silwood Park Campus), set out to assess the durability of UK grown Western Red cedar obtained from the Stourhead (Western) Estate in Wiltshire. Joanne compared this timber with Western Red Cedar samples sent from Canada and native Scots Pine (Pinus sylvestris).
Durability was determined using a laboratory based test in which sample blocks of wood were exposed to the activities of wood decaying Basidiomycete fungi (Coniophora puteana and Poria placenta). The second part of the study investigated the environmental profile of Western red cedar cladding made from UK and Canadian produced timber, using the ?Life Cycle Assessment (LCA) software Sima Pro.
Results from the decay evaluation showed that UK Western Red Cedar is extremely durable and in the same category of durability as samples from Canada. With regard to the LCA, UK grown Western Red Cedar had a superior environmental profile due mainly to the extensive impact that shipping timber from Canada has on the environment. Accuracy of this model, says Joanne, could be enhanced by further investigation, which would additionally reduce reliance on some of the assumptions currently contained in the LCA.
Overall, Joanne concluded that that Western Red Cedar is successfully grown in the United Kingdom, with regard to good durability of the timber and a favourable environmental profile. Questions regarding the quality of intensively produced timber compared to that harvested from ?old growth? forests requires investigation.
Further information from the Course Director: Dr Simon Leather, Department of Biological Sciences, Imperial College London, Silwood Park Campus, Ascot SL5 7PY. United Kingdom. Tel: +44 (0) 207 594 2316. Fax: +44 (0) 207 594 2339. Email: s.leather@imperial.ac.uk
Web site: http://www.imperial.ac.uk/biologicalsciences
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