Embodied Carbon: Another Challenge for Sustainable Construction

Sean Lockie
Property developers can influence embodied carbon emissions on their buildings.

Embodied carbon has been part of the sustainable construction debate for many years, but methodological challenges, the focus on in-use energy and carbon, and other sustainability drivers kept it low on the mainstream agenda. Embodied carbon is not the silver bullet to solving all our sustainability challenges, but it does have a place.

Other industries – water and highways, for example – now have a more mature approach to this challenge, with long-standing regulator requirements for embodied carbon assessments. However, buildings lag behind, possibly because they’re more complex in their design, and it’s difficult to predict how they’ll be used over their lifetime.

Embodied carbon is not the silver bullet to solving all our sustainability challenges, but it does have a place.

Most energy efficiency/carbon regulations focus on the reduction of CO2 emissions in their operation, rather than the 'embedded' emissions in the formation of the building elements (steel, glass, concrete, carpets etc). However, a building’s embodied carbon emissions are important too – these come from the CO2 produced during the manufacture, transport and construction of building materials, together with end of life emissions. For example, if concrete is specified on a project, then carbon was emitted when that concrete was made – during extraction of the raw materials, factory processing, and transportation to the construction site.

Traditionally, there was no agreement on exactly how embodied carbon should be defined and calculated. BS EN 15978:2011 (Sustainability of Construction Works) contains a framework, but it’s not user-friendly from a construction perspective. Faithful+Gould helped address this, as lead author of the RICS Methodology to Calculate Embodied Carbon (2014). Working with industry, we produced standard rules for straightforward, accurate calculation, and this guidance is now in widespread use in the property sector.

Source: RICS ModusSource: RICS Modus

In addition to our work on policy initiatives, we work closely with clients to put the guidance into practice, achieving significant improvements for their properties' carbon impacts. We recently engaged with British Land to help them understand the impacts of embodied carbon across their development portfolio.

Phase 1 saw an initial benchmarking assessment of British Land’s existing projects. We established an upper and lower embodied carbon benchmark for their new-build projects, divided into sub-structure, super-structure, external cladding and landlord mechanical and electrical.

The resulting mitigation strategies, including cement replacement and increasing the façade’s recycled content, produced an 8.2 percent reduction in embodied carbon, the equivalent of the energy used over 1.2 years.

This was based on analysis of seven buildings, using data from their respective cost plans. The benchmarks informed an embodied carbon assessment on the retrofit of 100 Liverpool Street, London EC2, to test the methodology. The resulting mitigation strategies, including cement replacement and increasing the façade’s recycled content, produced an 8.2 percent reduction in embodied carbon, the equivalent of the energy used over 1.2 years. In total the project achieved a reduction of 13.39 percent on the revised baseline, exceeding British Land’s original 10 per cent target. This excluded the benefit of retaining the original structure, which saved approximately 8000 tonnes of CO2, equivalent to 2.4 years of operational emissions.

Compared to new-build, the embodied carbon savings in the substructure were significant. Overall, each construction element achieves on average a 45 percent reduction in embodied carbon compared to a new-build British Land project. The overall retained structural elements for the project account for a 12.9 percent reduction on the total embodied carbon of a new-build project, for these key construction elements.

British Land Embodied Carbon BenchmarksSource: British Land Embodied Carbon Benchmarks

Good benchmarks at project outset was an important aspect of this work. British Land had invested in their own research and this gave them reliable benchmarks related to their own projects. We also found that it’s important to stick to the big issues – it’s unnecessary and impractical to have accurate figures for the entire building. It’s better to pick 10 items and maintain precise focus on those. The benefit of an experienced design team was also clear and, in this instance, the architect and structural engineer provided a wealth of supporting data to help with the process.

Looking ahead, we expect to see more developers and owners working with their suppliers to reduce embodied carbon, designing out material usage and specifying lower carbon sources of concrete, steel, rebar, aluminium and glass. This will help future-proof built assets and puts them ahead of regulatory requirements – although UK Building. Regulations currently focus on operational energy use, future legislative attention may well turn to embodied carbon.

Looking ahead, we expect to see more developers and owners working with their suppliers to reduce embodied carbon...

Some of the more progressive local authorities now take embodied carbon into consideration when making planning consent decisions. In central London, an embodied carbon assessment helps with planning negotiations, and Islington, Camden and Westminster are all calling for more analysis in this area. Typically, a carbon mitigation plan is required, showing accurate results of carbon interventions. Interventions will, of course, help with BREEAM scores too.

100 Liverpool Street, London EC2. Image courtesy of British Land

The British Land embodied carbon study is just one of the innovative sustainability services we recently provided to commercial property clients. A complementary initiative is our work with the Better Buildings Partnership (BBP) to develop a freely available sustainable fit-out toolkit for commercial offices and retail. This covers a much wider agenda, including health and wellbeing, biodiversity, and energy efficiency.

The British Property Federation and British Retail Consortium are part of the steering group for the BBP project, and the toolkit identifies cost-effective interventions and quick wins.