January 16, 2021

Build back better with timber

The UK government’s pledge to ‘build back better, build back greener’ rightly puts sustainable construction at the heart of the UK’s Covid-19 recovery. But to meet ambitious carbon targets, there must be a greater focus on the whole life carbon impact of building materials, and the use of wood has a major role to play in this, says Helen Hewitt, CEO of the British Woodworking Federation.

The government’s most recent package of environmental measures, including the Green Homes Grant – albeit aimed at stimulating the economy amid Covid-19 – are a continuation of its wider efforts towards decarbonisation and achieving net zero emissions. However, the Green Homes Grant brought disappointment with a focus solely on operational carbon and no guidance provided on the types of construction materials that have a low carbon footprint. This clearly illustrates that we need to look longer-term and the wider construction industry has a fundamental role to play.

Blueprints for recovery

Encouragingly, across all major industries, wide-ranging blueprints for carbon reduction have been published as part of Covid-19 recovery plans. The Construction Leadership Council’s Roadmap to Recovery includes the achievement of net zero carbon as a core pillar, including improvement of design, product selection and manufacturing and construction processes to reduce carbon output. RIBA’s 2030 Climate Challenge similarly targets carbon reduction through a focus on sustainable design. These approaches are vital to guide choices over the materials used in construction, as well as prioritising sustainable building products with lower embodied carbon and not just lower operational carbon. If we fail to adopt these practices, we risk falling well short of environmental targets.

The whole life carbon cost

A truly green building is one that takes both embodied and operational carbon into consideration. In simple terms, embodied carbon refers to the carbon footprint of the construction of the building, from the materials used to the impact of the processing, transport and energy consumption. It also encompasses the maintenance of materials that should be accounted for in the “working life” of a building, as well as the potential reuse, recycling and disposal methods of materials.

However, environmental impact in construction is too often thought of solely in terms of the direct energy rating of buildings, and how materials perform during their usage. Many building products can improve the energy efficiency of buildings, yet their manufacture may have higher associated carbon emissions and therefore a more negative environmental impact overall. In a new building, the embodied emissions from construction can account for up to half of the carbon impacts associated with the building over its lifecycle.  More broadly, each year around 48 MtCO2e or 6% of the UK’s total emissions come from embodied carbon, with more than half of this relating to the materials used.

So how do we move towards reducing embodied carbon in our buildings? Green building standards such as BREEAM, LEED v4, HQM and Ska help to assess operational carbon and are working towards including specific measures to regulate embodied carbon. But this on its own isn’t enough – there needs to be greater consensus and collaboration across industry, and regulation and incentivisation driven by government policy.

While operational carbon continues to be a policy focus, including energy efficient heating, too little attention has been paid towards embodied carbon and material choice. For example, the Green Hones Grant Scheme, while a positive economic stimulus, provides no guidance on the types of materials homeowners should use and how those with lower embodied carbon are preferable.

The role of timber in achieving decarbonisation

Timber is a truly sustainable and fully recyclable building material, and is therefore ideally positioned to help industry achieve net zero carbon by 2050. Using timber sourced from sustainable forests not only means that more trees get planted than harvested, but it’s a proven way to reduce carbon dioxide in the atmosphere as trees are effectively carbon stores. The Committee on Climate Change has cited the use of sustainably sourced wood in construction as “one of the most effective ways to use limited biomass resources to mitigate climate change.”

Helen Hewitt – BWF CEO

Timber products such as wooden windows have been proven to be more environmentally friendly than market alternatives. For example, the Wood Window Alliance (WWA) has commissioned several studies on the environmental credentials of wood window frames made to WWA specification. In a study undertaken by Davis Langdon to compare the embodied carbon emissions of WWA windows with equivalent PVCu frames, it was found that each wood window frame saved 89 kg CO2e when used instead of a comparable PVCu window frame. This is a saving of around three-quarters of a tonne CO2e per average house – the equivalent of driving around 6,500 kms in a small family car. Yet PVCu windows continue to be specified; this needs to change if we aim to build back better.

Initiatives such as RIBA’s 2030 Climate Challenge can play a major role here, by supporting architects to meet net zero (or better) whole life carbon for new and retrofitted buildings by 2030. Incorporating sustainably sourced timber – including windows and doors – into designs will help RIBA Chartered Practices meet these targets. The BWF also fully supports the Wood CO2ts Less campaign by Wood for Good, which is helping to educate the market on the benefits of sustainably sourced timber.

Education to overcome barriers

Outside of structural components, there is such an extensive range of available products for building elements including windows, doors, staircases and other fittings, which make selecting the best material an increasing challenge. To assist those involved in the design or construction of new or retrofitted buildings, the BWF has invested in an interactive CPDi programme focusing on the benefits and use cases of wood windows and doors.

The educational programme is broken down into bitesize chunks based on key themes, and each session can be taken alone, or as part of the wider series. Four modules are currently available to access free of charge, exploring the circular economy; the benefits of timber school buildings; building nature into architecture; and the natural evolution of the wooden window. Providing practical guidance and support with specification, the modules offer a comprehensive overview of how high performance, quality buildings can be created with the use of timber products, with a specific focus on windows and doors.

The target of net zero carbon by 2050 is ambitious, but it is achievable. Material choice is more important than ever, and industry must continue to collaborate, reach consensus, and share best practice if it is to succeed in meeting these goals.