The British Woodworking Federation Group
Whole-life carbon assessment – the only practical path towards Net Zero
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Whole-life carbon assessment – the only practical path towards Net Zero

Helen Hewitt, Chief Executive of the British Woodworking Federation (BWF), penned an article about the importance of ‘getting retrofit right’ for the report Why timber is leading construction’s Net Zero recovery, published by the Confederation of Timber Industries in the Summer. In this article, Helen used independent research on the Wood Window Alliance (WWA) specification to highlight how we need to look beyond operational carbon when we talk about low carbon alternatives in the built environment, and focus on the whole-life carbon assessment.

When talking about a building’s carbon emissions or carbon footprint, many people will be referring to the amount of carbon the building produces after its construction – in the form of fuel consumption, pollution and waste production. In terms of a circular economy, this is known as “operational carbon”. The Government’s Green Homes Grant Scheme has very much concentrated on operational carbon, much to the disappointment of many, like the BWF,  who believe that Net Zero needs a whole life carbon approach, taking into account both embodied and operational carbon.

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 and should be accounted for in the “working life” of a building. The potential reuse, recycling and disposal methods of materials should also count towards embodied carbon as part of a building’s whole lifecycle. The UK Green Building Council stated that ‘reducing embodied carbon is important for many reasons; not only for reducing resources and associated costs but also alleviating longer term risks around resource availability’ (UKGBC, 2015).


Why timber is the solution

As a building material, timber sourced sustainably is a great way to help the UK meet net zero carbon targets by 2050. Timber sourced from sustainable forests not only means that more trees get planted than cut down, but it’s a proven way to reduce carbon dioxide in the atmosphere. Wood products are carbon stores and growing forests are carbon sinks. This message is very much promoted by the leading timber industry campaigns Wood CO2ts Less and Time For Timber.

If we refer back to the original article that Helen wrote for the report Why timber is leading construction’s Net Zero recovery,  looking at retrofit she put the case that timber windows should be the material of choice for fenestration. To substantiate her argument, Helen quoted the Heriot Watt University independent study, where it was found that a typical wood window frame made to the WWA specification has a negative global warming potential over its estimated 56 to 65 year life service. Research shows that planned maintenance prolongs the life of the window and its carbon store effect, reducing the impacts caused by new replacements. Currently, wood is the only window frame material that can be repaired in such a way.

It’s encouraging to see that the retrofit agenda is here to stay. A material first approach and designing for the long-term are fundamental to a circular economy approach; helping to ensure that the whole life carbon cost is considered, and not just operational carbon. More detail on this can be found on the CPDi platform –

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The WWA Specification
Wood window frames made to the WWA Specification are carbon negative – they store more carbon than is produced manufacturing them.
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