Let’s get serious about embodied carbon, says BESA
The energy efficiency of buildings and products has improved dramatically over the past 30 years, but to protect the global environment we must also crack the more complex challenge of reducing ‘embodied carbon’, according to the Building Engineering Services Association (BESA).
The Association is marking World Environment Day (WED) on June 5 by drawing attention to the fact that the built environment still contributes more than 40% of total global carbon emissions. While regulations, greater use of renewables, and improved product performance have all contributed to a steady fall in ‘operational’ carbon ‘embodied’ carbon remains big blot on the global horizon.
This challenge fits neatly into WED’s ‘Only One Earth’ theme because without tackling embodied carbon it will be impossible to achieve the emission reductions needed to keep global warming below the 1.5degC target set by the UN’s Paris Agreement to avert catastrophic climate change, according to BESA.
The Association also welcomed the intervention of the parliamentary Environmental Audit Committee, which has called for mandatory whole life carbon assessments and priority to be given to retrofit and reuse of buildings.
The Committee chairman, Philip Dunne MP, said: “From homes to offices, retail units to hospitality venues, our buildings have a significant amount of locked-in carbon, which is wasted each time they get knocked down to be rebuilt, a process which produces yet more emissions.”
“Ministers must address this urgently…baseline standards for action need to be established. Mandatory whole life carbon assessments, and targets to crack down on embodied carbon, provide part of the answer. Constructors and developers can then determine which low-carbon materials, such as timber and recycled steel, they can use.”
The assessment, which the MPs want to see introduced by the end of next year, would calculate the emissions from the construction, maintenance, and demolition of a building, and from the energy used in its day-to-day operation. Holland and France already have mandatory whole-life carbon assessments for their built environment.
‘Keeping 1.5 alive’ was the slogan of the COP26 Climate Conference in Glasgow last year and buildings have repeatedly been picked out by the Committee on Climate Change (CCC) as a key challenge on the road to Net Zero.
Two thirds of the whole life carbon of a building is embodied. The first third is in the creation of the building and the second in the replacement of plant, facades etc. during its life cycle. The superstructure is responsible for about 40% and maintenance and refurbishment accounts for 32% of lifetime carbon.
“Working out the embodied carbon of a building’s structure has never been straightforward, but it is a walk in the park compared with the calculations needed to assess the embodied carbon of building services because of the complexity of our industry’s supply chains and technologies,” said the Association’s head of technical Graeme Fox.
“That is why building clients often take the path of least resistance and opt for some sort of ‘statement’ carbon reduction measure like a bolt-on renewable rather than digging too deeply into the maths needed to address the embodied carbon that would make a much bigger difference.”
The UK built environment is responsible for almost 166 megatonnes (Mt) of CO2 equivalent (the UK total is 414 mt) per annum – and the construction of a typical 6,000 sq m office emits approximately 4,000 tonnes of CO2e.
However, during a recent BESA webinar, Simon Wyatt, sustainability partner at the design consultancy Cundall, said embodied carbon was often regarded as “boring because it is about making things work well throughout the year – it is not about green bling”.
Fortunately, there is starting to be more “excitement” around the topic as more clients and engineers woke up to the fact that without more effort and innovation focused on embodied carbon and lifecycle building performance, we would have little chance of meeting our net zero built environment goals, added Wyatt.
There has also been significant progress in the field including a growing range of digital tools that can help engineers calculate embodied carbon more accurately. The availability of more complete data and better design methods also mean designers can provide more compelling arguments to convince clients of the need for greater investment at the front end of projects to significantly reduce lifetime carbon impact.
CIBSE produced the first comprehensive guidance for calculating the embodied carbon of building services (TM65) last year and this has breathed vital new life into the complex process of gathering relevant information from all parts of the supply chain.
It is also following the publication up with a range of methodologies for separate products and systems that will help project teams provide more accurate information to clients so they can make better informed decisions.
More manufacturers are also providing embodied carbon data, which makes it easier to calculate the impact of their products from manufacture up to installation. They are using Environmental Product Declarations (EPDs) or TM65 to provide the data. The RICS Built Environment Carbon Database is also an effective tool for calculating the embodied carbon of complete projects.
The world’s first universal cost standard for reporting embodied and operational carbon in the construction and lifecycle of buildings was also launched earlier this year. 49 professional bodies support the International Cost Management Standard (ICMS3), which is designed to help developers make more informed choices about materials and construction practices, and whether a building should be retrofitted or demolished and rebuilt.
And ultimately, the most carbon friendly approach it not to build at all, according to many experts.
“Reuse is better than rebuild. We have more than 600,000 empty buildings – 445,000 of which are residential,” said Dr Natasha Watson, senior structural engineer at the consultancy Buro Happold. “Covid19 has changed how we interact with buildings so we should re-assess how we service them and how we make better use of what is already there. We can repurpose far more.”
Speaking at another BESA webinar, she urged engineers to challenge the project briefs they receive more aggressively – and insist on a ‘design optimisation stage’.
“The earlier you tackle this issue, the bigger the potential savings,” said Dr Watson. “People are under increasing pressure to deliver projects more quickly and cheaply, but we cannot fully address embodied carbon without proper planning.”
She pointed out that the financial sector was committed to net zero “not necessarily for moral reasons but for business continuity” and that asset owners also recognised their properties would quickly become uneconomic if they did not address this issue. Local authority planners are also stepping up the pressure to address ‘whole life’ carbon before granting planning permission.
“Re-purposing an existing building is the Holy Grail of embodied carbon,” added Fox. “It is never possible to reuse everything but we should certainly try to reuse as much as possible from the foundations up including the superstructure where so much carbon has already been expended.”
Building services engineers, like everyone else in the supply chain, also need to design with deconstruction in mind so materials and system components can be recycled, reused, and more easily replaced as part of refurbishment and repair planning, according to BESA.
“We also need to do sensible things like use simple, reversible connections wherever possible, so it is easier to bolt in new components without having to remodel and disrupt the whole system,” said Fox.
“The building engineering sector deserves congratulations for taking major strides with product efficiencies and control strategies that reduce carbon in use, but if we are to make progress towards our bigger global environmental goals then embodied carbon will have to be tackled much more vigorously.”