SEEKING THE CONCRETE FACTS IN DEBATE
The Concrete Centre's claim that 'CO 2 emissions from timberframe constructions are actually higher than from modern masonry houses' (AJ 13.07.06) does not stand up.
Even before construction, timber has an advantage over concrete as a virtually carbon-neutral material. The manufacture of a timber house produces 28.1 tonnes of carbon emissions. That same volume of timber will have sequestered 25.5 tonnes of CO 2 during the tree's lifetime, giving a carbon footprint of 2.6 tonnes.
A masonry house uses about 25 tonnes of concrete for foundations and f loors, four tonnes of cement for mortar and rendering, with about one tonne wasted - altogether 30 tonnes of CO 2 emissions. A timber house thus starts its service life with a 27.4-tonne advantage over a modern masonry house.
The Concrete Centre asserts that concrete's high thermal mass ensures lower energy costs. High thermal mass is effective in climates with a high daily temperature range as it can stabilise the temperature within a building. But we live in a country with a low daily temperature range, which is set to decrease even further.
Buildings with high thermal mass are ineffective in winter; they take longer to heat up (with a consequent increase in the amount of energy used) as heat is absorbed by the material. And, in summer, once high-thermal mass material reaches its thermal capacity it radiates heat back into an already-overheated building.
In a recent study BioRegional concluded that a 23.3 per cent reduction in concrete and cement in favour of timber can lead to a saving of 7.8 million tonnes of CO 2.The concrete industry cannot claim credibly that concrete is sustainable. It should stop knocking timber and work with us to ensure the industry's carbon footprint is as small as possible.
Charles Trevor, managing director, wood. for good