Embodied carbon can be defined as all carbon emissions that are emitted during the construction of a new building. With an increase in the pressure to decarbonize the built environment and build more carbon-neutral buildings, the reduction of embodied carbon has become of great importance.
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Local authorities have also now begun to question developers and contractors on their carbon footprint during the construction of new developments. This has led to the need to understand what embodied carbon is and how it can be reduced for future projects.
Embodied carbon differs from operational carbon in the sense that operational refers to the carbon that is released once a building is fully completed and operational, whereas embodied carbon is the carbon emitted from the extraction of raw materials that are used to build, manufacture, and refine these materials as well their transportation, installation, and disposal.
The largest single contributor to greenhouse gasses (GHGs) in the building sector. In the United States, about 40% of the energy that was consumed in the year 2015 was used to directly or indirectly operate buildings. When embodied carbon emissions and energy from the materials and construction are added, the number is almost 50%.
Embodied carbon is not environmentally friendly and a few practices can be used in architectural or building practices to greatly help reduce the carbon footprint.
Measures to Reduce Carbon Emissions
The reuse of an old building as opposed to building a new one will typically reduce embodied carbon between 50% and 70%. This is especially true if the foundations and structural integrity of the building are still intact since this is where most of the embodied carbon resides.
Low carbon mixes with the use of fly ash, calcined clays, and slag can greatly reduce the amount of embodied carbon. It should be noted that access to these materials will vary from place to place, but the presence of something that can be used to reduce the carbon footprint for concrete mix is usually available everywhere.
Whenever possible, the use of lower-carbon alternatives during construction can help reduce embodied carbon. For example, if you can use wood at any stage during the construction of a building as opposed to concrete or steel for the same result it will be more environmentally friendly, as this reduces the embodied carbon emissions.
The review of environmental product declarations can greatly help developers and contractors in the selection of lower-carbon alternatives.
The reuse of salvaged building materials such as bricks, broken concrete, and metals typically have lower embodied carbon as compared to the emissions of carbon that is released to produce new concrete, new steel bars, or bricks.
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Another way in which embodied carbon can be reduced is by the selection of highly recycled materials, especially metals. This is because virgin steel will produce 5 times more embodied carbon as compared to that which is produced by recycled steel. This will also promote recycling and waste minimization.
Maximizing Structural Efficiency
As earlier stated, most of the embodied carbon lies in the structure of the building and foundations; therefore, maximizing structural efficiency by ways such as the use of wood framing methods, efficient structural slabs, and sections are effective methods that can be implemented to reduce embodied carbon.
Choosing carbon sequestering materials like agricultural products such as straw and hemp insulation can have a big impact on embodied carbon reductions. Unlike wood, hemp is annually renewable.
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Limiting the use of carbon-intensive materials, products like plastic, aluminum, and foam insulation have a very high carbon footprint. So even if aluminum may be aesthetically pleasing, limiting and limiting its usage for a building project may not be environmentally friendly.
Other ways in which embodied carbon can be greatly reduced by developers and contractors can include measuring the embodied carbon across the entire construction life cycle of a project.
Once this has been established, this can be used as the baseline to work towards net-zero embodied carbon. Adopting the best practices by contractors and developers would mean disclosure of supply chain information and the selection of material based on low embodied carbon impacts.
In summary, it is up to the developers to reduce the embodied carbon. They should measure the carbon across the entire life construction cycle of the project. Once this has been established, it can be used as a baseline and this value is used to reduce embodied carbon towards net zero.
Adopting best practices by contractors and developers would mean disclosure of the supply chain information and the selection of material based on low embodied carbon impacts.
Designers must build with a low carbon approach in mind. This should not just be limited to the carbon approach but also other aspects of the project such as energy, water, and material needs across the entire cycle.
Häkkinen, T. et al. (2015) "Reducing embodied carbon during the design process of buildings", Journal of Building Engineering, 4, pp. 1-13. doi: 10.1016/j.jobe.2015.06.005. Available at: https://www.sciencedirect.com/science/article/abs/pii/S2352710215300036
Strain, L., 2021. 10 steps to reducing embodied carbon. [online] Aia.org. Available at: <https://www.aia.org/articles/70446-ten-steps-to-reducing-embodied-carbon>
Rpsgroup.com. 2021. Embodied carbon: What it is and how to tackle it | RPS. [online] Available at: <https://www.rpsgroup.com/services/environment/sustainability-and-climate-resilience/expertise/what-is-embodied-carbon/>
Jones, E., 2020. 5 Ways to Reduce Embodied Carbon on Your Next Building Project - e-Builder. [online] e-Builder. Available at: <https://www.e-builder.net/blog/5-ways-to-reduce-embodied-carbon-on-your-next-building-project/>