July 30 2020
Sustainable Design: Capturing Embodied Carbon
As we continue to emerge from the global pandemic, we’ve been deepening our commitment to sustainability at Entuitive. In previous articles, we examined and analyzed post-pandemic projections for carbon emissions and discussed how deep energy retrofits are a great way to avoid spikes in carbon emissions post-Covid.
We see sustainable practices as being part of a holistic design and engineering process. As design engineers of both structure and building envelope systems, we have a responsibility to design with whole life carbon in mind and to continually seek ways to challenge the business-as-usual approach.
When we think of the built environment’s carbon emissions, we typically think of operational carbon, the amount of greenhouse gas emissions produced by a building in use. Smart design solutions, such as a high-performing building envelope, can reduce the amount of energy needed to operate a building, thereby reducing its GHG emissions.
But we must also consider embodied carbon, which is the amount of GHG emissions released by the construction of the building itself, such as during the manufacturing, production, and transportation of the required building materials.
The embodied carbon of buildings is responsible for 11% of global greenhouse gas emissions, and we can work towards decreasing that figure by measuring and analyzing the embodied carbon of proposed structures and developing sustainable solutions.
Lifecycle Assessments: Mid-Rise Office Building
Understanding the impacts of early stage design decisions on overall building performance has quickly moved from being a good idea for certain high-performance projects to an essential part of the architectural and engineering design process.
Lifecycle assessments (LCAs) assess the environmental impact of a project from beginning to end-of-life and beyond. Entuitive’s in-house technology enables us to extract building material quantities and information for use in LCA software, determining the areas where we can achieve the most significant carbon reductions.
The following case study illustrates the importance and value of embodied carbon analyses early in the concept and design phase of a project.
Entuitive is consulting on a private development project undergoing a renovation and expansion that is employing a high-performance building envelope, adaptive reuse of an existing structure, and mass timber design to achieve its deep sustainable design goals.
The hybrid timber, mid-rise office building is currently in the schematic design (SD) phase. Our team analyzed the embodied carbon of the propose structure and façade using the OneClick LCA software, focusing on the expansion portion of the project.
Our analysis found that the proposed expansion has a cradle to gate embodied carbon footprint of 669 tons of CO₂e, measuring about 176 kgCO₂e/m². The cradle to gate figure covers the material product stage, which comprises raw material extraction/supply, transport to the plant, and manufacturing.
Further phases of a material’s lifecycle include the construction stage, in-use stage, and end-of-life stage. In this analysis, we focused on the material product stage as the project is still in SD.
To complete our estimate, we looked to the The London Energy Transformation Initiative (LETI), which estimates that the material product stage for commercial office buildings composes about 48% of the structure’s total embodied carbon. Using this figure, we estimated that our case study structure’s total embodied carbon is about 367 kgCO₂e/m².
Case Study Conclusions
What can we learn from this figure? We know that the hybrid timer-concrete system of the expansion is partly to thank. A 2012 study published in TheStructuralEngineer found that the embodied carbon of a fully concrete mid-rise office tower is about 500 kgCO₂e/m². While a different analysis tool was used, this demonstrates a 36% increase in carbon from our hybrid structure.
Among other material decisions, the LCA helped us determine that if Portland Limestone Cement were to be used in lieu of Portland Cement, and the concrete were to be made up of more than 35% supplementary cementing materials (SCM), the total embodied carbon of the building would decrease by 15% to about 311 kgCO₂e/m².
Our Advanced Performance Analysis team also performed a building performance analysis and found that the greenhouse gas intensity (GHGI) is 3.8 kgCO₂e/m²/year. This means that it will take nearly 100 years for the operational carbon of the building to amount to the level of the structure’s embodied carbon.
As enhancements in energy efficiency decrease operational carbon over time, we can see that addressing embodied carbon becomes ever more important. In order to meet the 2030 climate targets, we must act now to reduce the embodied carbon of the buildings and structures we design.Measuring and analyzing a project’s embodied carbon as early as possible can help design teams make smart, informed decisions about a project and its materials, whether it’s a new build or renovation. Strategies may include material re-use, selecting an optimized and efficient framing scheme, such as the hybrid timber scheme above, and carefully specifying materials.
By considering the embodied carbon of a building, and not just the operational carbon, we can greatly reduce the environmental impact of the AEC industry.
Sustainability at Entuitive
Sustainability is a process, not an add-on. Working smartly and efficiently means minimizing waste and using innovative materials and technologies, all towards cost savings for our clients and better sustainability outcomes for our communities. Our LEED®-accredited staff and Certified Passive House Designers are committed to design processes that use materials and resources wisely, meeting project needs with a reduced-waste impact on the environment.
Further, our team is continually developing in-house tools to better assess embodied carbon in our projects. For example, we recently developed a tool to estimate a project’s embodied carbon as early in the concept phase as desired, which will allow us to make design decisions early on to achieve higher carbon reduction potential.
For more information reach out to Emily King and our Sustainable Performance Group.