Decarbonising construction

Michael Bennett and Amber Wright explain the importance of reducing embodied carbon in construction - putting forward the case for legislative reform and how new technologies, methods and contracts are supporting the living sector’s move to net zero.    

To date much of the government’s focus to meet its net zero targets has been on creating more energy efficient homes and buildings. While important, steps must also be taken to improve sustainability throughout the lifespan of a building.

One way to do this is by reducing embodied carbon emissions during the construction of buildings.

Embodied carbon

Embodied carbon is the carbon dioxide (CO₂) emitted through producing materials. For example, embodied carbon may be created in the production of clinker, used to make cement, or by the burning of gas to make steel in a blast furnace.

Embodied carbon is particularly significant in construction, as the production of steel and cement makes up between 16% and 18% of global CO₂ emissions annually. There are currently no mandatory UK limits on how much embodied carbon can be emitted during the construction process.

In February 2022, a Private Members Bill was introduced into Parliament with the aim of monitoring and limiting embodied carbon emissions in construction projects.

When presenting the Carbon Emissions (Buildings) Bill to Parliament, Duncan Baker MP stated that a third of carbon emissions come from construction, with 40m to 50m tonnes of greenhouse gas emitted annually as a result of the construction, upkeep, refurbishment and demolition of new and existing buildings and infrastructure. Baker stated this is known as embodied carbon, “so called because the materials that we build are the physical embodiment of such greenhouse gas emissions”.

Regulation

The Bill sought to set limits on embodied carbon emissions in the construction of buildings and to require that the whole life carbon emissions of buildings be reported. The Bill’s passage through Parliament was cut short and was withdrawn after its first reading.

While it is rare for a Private Members Bill to progress through Parliament and become law, the Bill’s introduction reaffirmed the importance of regulating embodied carbon emissions in construction.

In 2021, the UK Green Building Council launched a ‘Net Zero Whole Life Carbon Roadmap’. Over 100 organisations contributed to the Roadmap and one of the recommendations to achieve net zero across the sector is the regulation of embodied carbon for new buildings and major refurbishments. 

The Roadmap recognises that the measurement and mitigation of embodied carbon is currently voluntary and recommends introducing limits for embodied carbon across all sectors by 2027.

Many in the industry have shown support for the proposed Building Regulation amendment ‘Part Z’ and Approved Document Z. The documents were put together by members of the industry as a proof of concept of the regulations that are needed to put legal limits on the embodied carbon emissions of major projects, while outlining requirements on the assessment of whole life carbon emissions. 

What else could be done?

Another option that has found favour in several countries is the requirement for developers to undertake carbon impact calculations during planning.

The calculations could then be used by a planning committee either as a criteria for granting approval, or by imposing conditions in relation to carbon offset. To ensure ongoing project viability for developers, any such approach needs to be flexible and fair.

New technologies are also being developed all the time that could significantly reduce the levels of embodied carbon. For example, JCB recently announced that it is targeting the sale of hydrogen powered diggers by the end of 2022. There are also options for low carbon concrete and zero carbon steel production that could significantly alter the emissions calculations for a new development.

Some may argue that adopting new technologies, materials or construction methods is a more effective and realistic option, as the planning stage is often too early to commit to embodied carbon emissions limits considering a building’s design at this stage may not contain sufficient detail.

Contracting for embodied carbon emissions

Whether limits on embodied carbon in construction projects become a legal requirement or the industry continues to strive to increase sustainability, drafting to achieve certain environmental objectives is likely to become a common feature of construction contracts.

Contracts can set out clear targets for embodied carbon emissions, how these will be calculated and monitored, as well as allocating the risk and consequences of these targets not being achieved.

Other options to improve the environmental credentials of a project may include:

• Auditing at the tender stage to ensure minimum standards are met by the supply chain in relation to sustainability.

• Contractual provisions requiring a supply chain to meet specified net zero project targets and offering incentives if emissions can be further reduced.

• Requiring a supply chain to adhere to sustainable working practices throughout a project. For example, reducing the carbon footprint of plant and equipment, using sustainable materials, promoting biodiversity and setting carbon limits on staff travel and material sourcing.

Support for sustainable construction

Sustainability is on both the construction industry and government’s agenda and it’s likely that those operating in the sector are going to come under increasing pressure to reduce the carbon emissions of projects from funders, future purchasers or tenants.

The industry is, however, responding and the advent of new technologies, materials or innovative contracts show the progress that is being made. Decarbonising construction is reliant on accelerating these efforts, while moving on from just making buildings more energy efficient.

Reducing embodied carbon emissions must be considered critical on the journey to net zero.

This article features in Shoosmiths’ new report: Operating in living