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NO TIMBER BULLET FOR NET ZERO
Using more wood is key to decarbonising construction, but it must be sustainably sourced and used to make the most of the resource, says Volkan Doda, head of design technologies at environmental design consultants and engineers Atelier Ten
Wood products are regaining popularity as sustainable alternatives to steel and concrete construction, fuelled by concern about the latter’s outsized environmental impact. Wood is not just an easily workable material with lower environmental impact than most alternatives. While the atmospheric carbon stored during the trees’ growth reduces buildings’ environmental footprint, its use in buildings reinforces a connection with nature for users. Today’s innovative engineered wood products and construction techniques enhance the traditional capabilities of wood, turbo charging this growth in popularity. Yet not all wood products are created equal and not every use of wood is sustainable. Building design, procurement, and end-of-life considerations are essential for buildings to maximise the benefi t of wood products whilst protecting source ecosystems. Wood products are rarely one-for-one replacements for other construction materials and require careful building design. They are generally less suitable for use with large structural spans and moisture protection, vibration and acoustic behaviour, and fi re (and insurance) related risks are essential considerations. These can often necessitate additional treatments and materials that can be carbon intensive, working against some of wood’s environmental benefi ts.
Sustainable timber sourcing and replanting are prerequisites for the environmental benefi ts to materialise. When it comes to sourcing timber, only 30% to 50% of a mature tree mass can be used for construction grade lumber. To secure net benefi t beyond
the system boundaries of a construction product, most of the remaining mass needs to be managed equally sustainably. This is not always possible as signifi cant amounts decay in the ground or are incinerated, releasing carbon.
In addition, an indiscriminate adoption of wood in construction risks demand exceeding supply from current sustainably managed forests. Whilst some global regions may have surplus capacity, the quality of this surplus varies, and it can take decades to increase capacity of high-quality architectural wood production sustainably. And the UK already relies on imports to meet its wood products demand.
Another fundamental consideration is what happens to stored carbon once a wood product reaches end of life. Here, some scenarios (managed landfi lls) are better than others (incineration). One certainty is that a signifi cant amount of the stored carbon needs to be discounted or transferred over to other benefi ciaries at end of life, limiting the accounting of this benefi t within the system boundaries of individual uses. If used effi ciently and effectively, the net global
benefi ts of sustainably sourced wood exceed these limitations, and timber remains a crucial tool in our construction arsenal in the fi ght against climate change and environmental degradation.
As the next generation of engineered wood products emerge, we will likely overcome some of today’s challenges. Yet sustainably managed wood products will remain a limited resource, and to maximise their inherent benefi ts we will need to work with the awareness of both the benefi ts and the challenges of their use in construction. ■
www.ttjonline.com | September/October 2024 | TTJ
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