Timber structures Sustainability
Affordable low-carbon timber homes: a balancing act Jae Cotterell outlines the challenges of construction budgets versus sustainability.
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any think that a sustainable, climate-ready future requires new housing to be built using timber, wherever feasible. This reflects a significant shift from the belief that energy efficiency alone would be required, and we are beginning to appreciate that embodied carbon is also critical to reduce carbon emissions sufficiently. The UK building culture has been rooted in masonry construction and in recent decades there have been modest increases, across all sections of construction, in the amount
of insulation used, generally using high embodied carbon insulation. The necessary shift of emphasis towards timber structures reflects its low-carbon and renewable credentials. Building in timber frame also enables use of modern methods of construction (MMC), which assist with erection speed, quality control systems and waste management. With the need for highly insulated and airtight homes, timber can offer carefully targeted solutions, instead of simply tweaking traditional construction methods. The potential benefits to the environment are significant. However, there are caveats and pitfalls to be avoided, or at least carefully considered. Here are three examples where specifying timber and claiming eco-credentials must be carefully balanced against environmental impacts and the potential for elevated costs.
Protecting limited resources First, there is the over-use of timber itself – it is after all a limited resource, and we suffer from a lack of biodiverse forests both worldwide and in the UK. Planting for use as a ‘product’ is not the same as enlarging existing established woodland, and we need to keep this in mind. Allocating large areas of land for single growth ‘tree farms’ reduces land available for biodiversity and other activities such as supporting generation of renewable energy and increased local food production – land is under great pressure in the context of building a decarbonised economy. When specifying timber, we must consider resource efficiency and newer timber products; using laminated veneers such as I-joists can be a good fit for smallscale developments as they enable minimisation of structure and maximisation of insulation.
Figure 1: Small section I-joists using laminated veneers. Photo: Passivhaus Homes Ltd
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Claims of carbon offsetting through sequestration in the timber elements can be misleading and could simply reflect extravagant use of the timber itself. Certainly, if we are looking at affordable housing and switching to timber frame construction, appropriate >> Timber 2022
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