Embodied carbon is the carbon footprint of producing materials. It is steadily gaining attention from both industry and parts of government, where it is now recognised that embodied carbon emissions make up a large fraction of the emissions from the construction sector. In fact, it’s often 20-40% of the whole life (embodied + operational) carbon emissions of a new building. This is already a significant proportion and will only increase as the thermal standards of new buildings improve.

Unlike operational carbon emissions, embodied carbon cannot be reversed. Once they have been released the opportunity for improvement has passed. In contrast, if a building is constructed with poor operational carbon emissions, whilst it is not ideal they can still be improved, at any point in the lifetime of a building, for example by implementing a range of energy efficiency measures. Embodied carbon reduction is therefore a onetime opportunity. To be taken, or to be lost, forever.

Reducing the embodied carbon of buildings can make a valuable contribution to reducing global greenhouse gas emissions. It is often possible to reduce the embodied carbon of a building by around 20% in a cost neutral manner, starting with simple and cost effective reduction measures.

In fact, experience from the infrastructure sector shows that if it is implemented in the correct way embodied carbon assessment can be cost positive. This was explicitly stated in the HM Treasury’s Infrastructure Carbon Review:

“Leading clients and their supply chains have already achieved reductions in capital (embodied) carbon of up to 39 per cent, and 34 per cent in operational carbon. These reductions in carbon have been achieved in association with average reductions in Capex of 22 per cent."  

HM Treasury

The challenge was therefore to translate such strong evidence into the building sector.

CLS Holdings embarked on an embodied carbon assessment of their Spring Mews development, which is a mixed use scheme in London. The new build development consists of student accommodation (378 x rooms), 7 x micro office space and Hotel (93 x bedrooms) totally 165,000 sqft/NLA.

The embodied carbon assessment of Spring Mews was undertaken by the consultants Circular Ecology. The assessment provided the following carbon hotspots:

• Production of materials = 76% of embodied carbon
• Construction waste = 13%
• Site energy = 10%
• Transport of materials = 1%

The main carbon hotspot was therefore the embodied carbons of the production of materials, which were broken down further in the below (note the below figure only covers the production of materials breakdown):

The breakdown of materials was therefore diverse. However, categorising these into larger building elements helps to know where the future focus would be best placed.

The main carbon hotspots were:

• Foundations = 17% of the total embodied carbon
• Building envelope = 22%
• Upper floors and roof = 21%
• Construction site = 23% (10% site energy, 13% site waste)

The embodied carbon of construction waste is often a surprisingly notable contribution to embodied carbon results and is an important hotspot for improvement. As a result, CLS Holdings are currently assessing the embodied carbon profile of the demolition of a building, to determine the main carbon hotspots at the end of building lifetime.

The value of undertaking such an embodied carbon assessment is that it provides CLS Holdings with an understanding of where to focus on future developments. It also provides a better understanding of the absolute carbon (operational and embodied) impact over the life of the building.

Rowan Packer, Group Sustainability Manager at CLS Holdings, said:

“As a result of the project and working with Dr Craig Jones, we now review and consider the building materials of all our projects, wither it be construction, refurbishment, Capex replacement or demolition. Having a better understanding on embodied carbon allows us to have a greater engagement with our supply chain and also opens conversations on scope 3 emission by default. This in my view is a positive step forward.”

This article was written by Dr Craig Jones, Director at Circular Ecology, on behalf of CLS Holdings plc.