The low-carbon diet
Is frame-flexibility the key to avoid the life-cycle carbon yo-yo effect?
The built environment is responsible for a third of the UK’s carbon emissions, and radical change in building and infrastructure design is urgently required if we are to truly make an impact on climate change. It is widely recognised that embodied carbon makes up a fifth of this sector’s overall footprint.
Through the Climate Change Act, passed in May 2019, the UK government has legislated to achieve net zero carbon by 2050. To help deliver this, both the UK Green Building Council (UKGBC) and London Energy Transformation Initiative (LETI) have challenged our industry to strive towards delivering net zero carbon buildings by 2030.
UKGBC’s research advises that a third of a building’s carbon footprint results from operational energy consumption, whilst the remaining two-thirds are associated with the building’s initial design, procurement and construction, together with its ongoing maintenance and adaptation. Whilst the engineering community have made good progress in technological advances to reduce operational carbon emissions, tackling a building’s embodied carbon remains a major challenge.
To pave the road to zero carbon, embodied carbon metrics must be given priority over traditional measures of project viability, such as cost and efficiency. Developers are responding to this, recognising that occupiers are increasingly demanding more sustainable buildings which accord with their corporate and social responsibilities, alongside the values of their customers and employees. These identity markers are changing the way the buildings are valued, with evidence suggesting sustainable assets can yield a higher return on investment.
Spurred-on by this challenge, our multidisciplinary team, Chloe Souque, Richard Whitehead and Mark Terndrup, investigated the comparative embodied carbon of traditional structural frame solutions with that of timber-based alternatives. Through a thought-provoking high-level study, we explored four common structural options: steel frame with a holorib deck; steel frame with lightweight concrete holorib deck; traditional reinforced concrete frame; and reinforced concrete frame with post-tensioned (PT) slab.
We then compared these with more recognised sustainable solutions such as cross-laminated timber (CLT) with glulam timber beams and, finally, a hybrid of CLT with steel, often used to bridge the gap created by the structural limitations of timber frame construction.