By: Jessica Martinez, PE, LEED Green Associate, Project Manager for DCI Engineers

When considering the contribution of the building industry to global greenhouse gas emissions, it’s apparent there is a huge opportunity for structural engineers to help lower the sector’s carbon footprint. Currently, about 40% of global CO2 emissions are attributed to the building industry with 28% coming from operational carbon and 11% coming from embodied carbon.

Operational carbon pertains to the emissions created during the building’s daily operation and energy consumption while embodied carbon refers to the emissions associated with the creation of building materials and construction of the building. Operational emissions can be reduced over time with energy efficiency renovations and the use of renewable energy, but embodied carbon is locked into the atmosphere as soon as the building is built. Based on current building design standards, it takes approximately 30 years for the operational carbon produced by a building to equal the amount of embodied carbon emitted from the construction of the building. This means that the quickest way our industry can tackle global warming now is by targeting embodied carbon. Looking ahead – the world will build the equivalent of one New York City a month until 2060, so the decisions we make now in the construction of our buildings are imperative to the future of a sustainable building industry.

The most embodied carbon lies with the materials that require the most energy to produce – the structure. In fact, about half of the embodied carbon in a typical office building comes from the superstructure and substructure. In 2019, the Carbon Leadership Forum, American Society of Civil Engineers and the Structural Engineering Institute recognized this and created the SE 2050 Commitment to eliminate the impact of embodied carbon when considering all stages of a building’s life cycle by the year 2050.

In addition to generally minimizing overall material use in structural design to lower embodied carbon, the most common building materials – steel, wood, and concrete – have their own unique environmental impacts and associated embodied carbon reduction strategies that should be considered:

  • Steel: While other products can only be downcycled, steel can be recycled repeatedly into new members without any loss of quality. Because steel is so commonly recycled, the factor that controls its embodied carbon footprint is the energy grid tied to the manufacturer. In response, manufacturers are working on phasing out fossil fuel resources and turning to increasingly more clean energy sources such as wind and solar electricity to power their facilities.
  • Wood: Trees naturally sequester carbon throughout their lifetime by storing CO2 from the air in their mass, roots and surrounding soil. Once those trees are cut down and used to construct the building, that carbon is locked into place, making this an incredibly effective sustainable building material. However, wood can only be as sustainable as the processes used to harvest, manufacture, and replenish the final product. To minimize the amount of embodied carbon associated with wood construction, it’s important to use materials sourced from sustainably managed forests.
  • Concrete: This material has an immense carbon footprint because of the high-energy process required to make the binder portland cement. To reduce the amount of cement needed in the mixture and associated embodied carbon impacts, recycled by-products such as slag and fly ash and specialty admixtures are commonly used to substitute cementitious material. Most importantly, concrete specifications should be tailored so the supplier has the freedom to create efficient concrete mixtures that meet performance requirements instead of using traditional prescriptive specifications.

To optimize embodied carbon impacts, it’s important to get the entire project team and especially the structural engineer involved early in the design process. The building often takes shape way before many players get involved in the schematic design, but the team should be working together early in the project to consider the impacts of building form and structural materials in project decisions. Communicating project sustainability goals with the builder should also occur as early as possible to ensure the intended materials and methods are viable, regionally available and incorporated into the budget. Some builders are still adapting to new sustainability innovations, like low carbon concrete and mass timber construction, so additional time should be anticipated to overcome learning curves and allow for coordination.

However, the biggest carbon reduction strategy is to perform a Life Cycle Assessment (LCA), which quantifies the environmental impacts of a building throughout its entire life cycle – from resource extraction, through end-of-life and beyond. This data should be collected at various milestones throughout the project, depending on scope and scale, to allow building designers to communicate the environmental impacts of prospective design decisions with the rest of the project team. LCAs utilize individual Environmental Product Declarations (EPD), for each building material to determine the overall impact of the entire building. EPDs provide comparable information about the environmental impact of products, like a nutrition label, and vary in specificity. In Texas, we primarily rely on industry-average EPDs, but as sustainable markets become more competitive, we can expect to see an influx of more accurate, product-specific EPDs in the future

In certain parts of the country, policymakers are starting to pay more attention to embodied carbon by setting up environmental impact limits and taking steps to promote reduced carbon products. For example, here in our own backyard, the Austin City Council set an ambitious target back in 2014 to reach net-zero community-wide greenhouse gas emissions by 2050. In the scope of embodied carbon, this plan will incentivize lower-carbon materials and whole building life cycle design, while also educating stakeholders on best practices and partnering with local markets to decarbonize high-impact materials.

Meanwhile, on the West Coast, the State of Oregon adopted a program in 2016 that started providing free resources for concrete producers to report the environmental impacts of their products and cost reimbursement incentives. These incentives have since helped promote the growth of low carbon concrete markets and contribute to the stabilization of cost premiums. Then in 2019, farther south in the Bay Area, Marin County took their reduced carbon initiatives one step further and adopted the world’s first building code which includes a set of requirements that limits the greenhouse gas emissions of concrete while still maintaining its strength and durability properties for both residential and commercial construction.

And finally, the first major piece of embodied carbon legislation ever enacted – the Buy Clean California Act – was passed in 2017. Starting July 1st, 2022, new public projects in California are required to meet environmental impact limitations for structural steel, rebar, glass, and mineral wood board insulation. Buy Clean Colorado was also passed earlier this year and there are efforts to introduce and reintroduce this legislation in other states such as Oregon, Minnesota, and Washington, so it’s only a matter of time until these regulations are more standard across the country.

As for the market, investors are becoming increasingly aware that they need to focus on the triple bottom line to maximize success – meaning they can’t focus solely on profit alone but must also consider the social and environmental impacts of their investments. With this in mind, developers are actively looking for ways to showcase sustainability commitments in order to attract these investors. Most developers turn to green building rating systems, which are the most standard way to showcase baseline sustainability, and recently these organizations are taking interest in increasing the credits earned for embodied carbon reduction. Engineers should understand their key role in addressing this demand in the marketplace and take action. By coordinating with the project team early on to capture and track significant carbon savings, structural engineers can help developments showcase sustainability efforts at little to no cost.

To learn more about how to incorporate sustainable considerations into your structural designs, get involved with your local Carbon Leadership Forum hub and consider signing up for the SE 2050 commitment: