March 30, 2023

Structures and sustainability: pursuing net-zero carbon emissions

Jeseritz

The impact of a building’s construction and operations on carbon emissions has been well established by the AEC community. “Buildings, in fact, contribute 40% of the CO2 emissions worldwide,” according to the Carbon Leadership Forum. Much of the emphasis has been on reducing the operational energy consumed by a building during occupancy.

As buildings become more energy efficient and achieve net-zero energy consumption, interest is shifting to tackle the environmental impact of a building’s structure, exterior envelope and interior finishes. With the amount of building construction anticipated to occur over the next several decades, and the understanding of their associated environmental impacts, it is paramount that the AEC community continues to actively work toward embodied carbon reductions and sustainability in our built environments.

LESSONS LEARNED

In 2019, SEI launched the SEI Structural Engineers 2050 Commitment Program. The program enlists coalition partners who commit to work to educate, engage and report the environmental impacts of the built environment and its associated embodied carbon. Each SE 2050 coalition partner develops an internal embodied carbon action plan (ECAP), a document that outlines how each firm proposes to reach the commitment program’s goals. The ECAP is critically important, serving not only as a roadmap, but helping to develop a culture that will engage sustainable solutions.

Images courtesy of Perkins & Will [enlarge]

PCS completed life cycle assessments for two tower additions at the Swedish First Hill Campus.

In addition, the ECAP provides a framework for integrating lessons learned as the firm works toward its goals. PCS identified three areas in its ECAP to address education, reporting, reduction strategies, and advocacy: materials sourcing, client communication, and life-cycle assessment (LCA).

MATERIALS SOURCING

Concrete, for example, provides structural engineers with multiple strategies that reduce the embodied carbon of our mixes, and typically they don’t add cost to the client. Some of the tactics PCS has explored include Type 1L cement, mixes using large quantities of supplementary cement materials (SCMs) and utilizing performance-based concrete specifications.

Recent supply chain and production issues have created a challenge to obtaining regionally sourced Type 1L cement and SCMs. We’re beginning to see our Type 1L cement shipped from Taiwan. We’ve learned, however, that using mixes with Type 1L and SCMs — even when shipped from overseas — typically results in better embodied carbon reduction than not using Type 1L or SCMs at all.

We’ve been working closely with different concrete suppliers on alternative SCMs and strategies that help achieve our embodied carbon reduction goals for concrete: Working with suppliers to maximize the water-to-cement ratio in concrete through performance-based concrete specifications also is effective for reducing embodied carbon in the mixes.

CARBON REDUCTION

Embodied carbon reduction advocacy provides opportunities to add value for clients. Sustainable building programs such as the Leadership in Energy and Environmental Design are beginning to include points and design guidelines that measure, quantify, and reduce a building’s embodied carbon. As structural engineers, we bring new tools and strategies to quantify and identify a project’s high embodied carbon areas and offer clients and owners solutions to mitigate the associated embodied carbon and meet their sustainability goals.

To help clients make informed and sustainable decisions from the beginning of the project, PCS created “PCS Sustainability Design Considerations,” a document listing carbon reduction strategies that can be implemented for several structural systems and materials. The information provides practical guidelines and builds awareness about the impact of early structural decisions to sustainability.

In fact, considering and measuring a structural system’s embodied carbon as early as possible in the design process opens more reduction strategies to the design team. By selecting the appropriate structural system early in the design phase, meaningful reduction strategies can be used as the project progresses through the design phases into the construction phase.

Depending on the owner and design team, certain sustainability strategies may naturally align, and an efficiently laid out structural system can match their programming space requirements. When presenting structural system options on any project, we can include the embodied carbon intensity, which helps build embodied carbon literacy. We’ve found that often clients will include embodied carbon reduction in their decision process when presented with the information. Even if the client doesn’t use the information, the embodied carbon intensity number sparks conversation.

LIFE-CYCLE ASSESSMENT

The life-cycle assessment examines a building’s environmental impacts within its lifespan. Performing an LCA is complex, but it is easily learned. Some of the challenge comes when using a structural building information model, which has the capacity to generate a large — or minimal — amount of detailed information. The assessment requires an understanding about what elements are in the building model and which need to be included in the assessment.

We learned that engineers who were more knowledgeable about the structural system than about the LCA process tended to complete an LCA more efficiently than engineers who knew the LCA process but were unfamiliar with the project. To help make learning LCA software more accessible, we created a guide with tips and tricks that walks engineers through the LCA process and assigns parameters for different structural materials.

Structural engineers have an important role in the pursuit of net-zero by 2050. Some suggest it’s an unachievable goal. We think not trying is the untenable choice, and within the framework of an embodied carbon action plan, we set achievable goals and bring the very best of our skills to innovative solutions in the AEC industry. We’ll take the lessons learned … and push toward the goal to achieve net zero embodied carbon by 2050.

Chris Jeseritz is a project manager at PCS Structural Solutions.

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