Seeing the wood for the trees

Policymakers and the built environment industry should prioritise the responsible use of timber and biobased materials as a climate and nature solution.

The built environment accounts for around 40% of global greenhouse gas (GHG) emissions and a similar proportion of natural resource use, making it a critical sector for tackling climate change, and the twin crisis of biodiversity loss, while delivering sustainable development. Approximately 25% of built environment-related emissions are currently attributable to the embodied carbon in construction materials, (the majority of which can be attributed to concrete and steel which each account for approximately 7% of total GHG emissions), and as buildings become more efficient in operation and energy is decarbonised, that is rising to around 50%.

Mainstreaming the use of low-carbon materials and finding other innovative ways of radically reducing the embodied carbon of buildings is therefore an urgent priority. Construction timber can provide an important part of the solution with a ‘triple S’ value: carbon is sequestered as the trees grow; timber can substitute more carbon intensive materials; and it can store carbon for long periods of time. In other words, construction timber can be a highly cost-effective, natural carbon capture and storage technology if used in the right ways.

The monetary cost of carbon is set to rise rapidly through the introduction of carbon taxes and the value of carbon removal and storage will increase as we see demand grow.? Therefore, increasing the use of timber for construction can also increase the economic value of forests and attract additional investment in their sustainable management and expansion through appropriate restoration and reafforestation.

However timber use in construction is not a panacea, and forests are a precious resource for people, nature and the climate globally. For the benefits of increasing the use of timber in construction to be fully realised, and potential risks to both climate and nature mitigated, the following steps are necessary to ensure this is an holistic and genuinely sustainable solution.

• The need for new buildings should be questioned as a precursor to any new development. Could the need be met in a different way, and/or could existing buildings be renovated, or extended using low-carbon materials instead? Demolition of existing buildings can be very expensive in carbon terms, given the likely embodied carbon in concrete and steel structures.
• ?Where new buildings are needed, they should be constructed using very low-carbon materials including sustainably sourced timber and other natural, biobased materials. There needs to be a robust Life Cycle Assessment (LCA) methodology based on accurate data to enable ‘like for like’ comparison between different materials to inform the selection of the best, lowest embodied carbon options. There also needs to be an informed assessment of the comparative upstream impacts on biodiversity to enable an holistic understanding of relative impacts of different material choices on both climate and nature.
• Construction timber should be sourced, where possible, from secondary, re-used wood. Virgin timber should only be harvested from sustainably managed forests, independently certified by credible bodies such as the Forest Stewardship Council (FSC) or PEFC whose standards should be regularly reviewed to ensure forest management delivers optimum benefits for nature, climate and local communities.
• Long-term uses of wood such as construction should be prioritised and incentivised over short-term uses such as paper and packaging, or burning for energy production, which quickly release carbon emissions back into the atmosphere, to maximise its carbon storage potential.
• Timber buildings should be designed for disassembly, to facilitate re-use of timber components in successive buildings at the end of an individual building’s life. Subsequently there should be a systematic cascade of uses of the timber (through the production of particle board, fibre board etc), to maximise its lifespan and the duration of carbon storage.
• Timber for construction should be used in the most efficient ways through careful design and production techniques to minimise waste and optimise its use alongside traditional materials such as concrete and steel, and other bio-based materials with complementary applications such as insulation.
• Accounting for carbon sequestered, substituted and stored needs to be done rigorously and transparently. This must ensure that ownership rights to claim stored carbon in buildings is clear and not double counted as could happen if credits have already been sold for carbon offsetting on the voluntary carbon market during initial forestry activities or included in governments’ national determined contributions (NDCs) under the Paris Agreement.

Construction timber and other biobased materials can and should play an important role in radically reducing the carbon footprint of the built environment whilst increasing benefits for people and nature. Given the current scale of that footprint, and the projected growth of development and urbanisation over the coming decades – the number of buildings worldwide is set to double by 2050 - it is imperative that these solutions are embraced as a global priority by policy-makers and the built environment industry.