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Thornton Tomasetti’s Long Carbon Experience

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A firm-wide goal to lead the industry in the reduction of embodied carbon in structures

by Amy Hattan
Vice President for Corporate Responsibility, Thornton Tomasetti

Nine years ago, I  I became the first Corporate Responsibility Officer at the engineering services firm Thornton Tomasetti.. My earliest task was to manage the annual reporting required for members of the American Institute of Architects (AIA) 2030 Commitment – and to engage in this reporting with a unique twist. The Commitment, whose members are mostly architects, asks that member firms submit the predicted energy use intensity for their projects. At that time, my firm was primarily engaged in structural engineering, and measuring the operational energy of our projects did not seem to be the best assessment of our direct contribution.  Because of the large impact of structural materials on a building’s carbon footprint, we proposed to the AIA that we would report on the embodied carbon in our structural engineering projects. Thus, we began our multi-year R&D project on embodied carbon.

Over the course of our years as a member of the Commitment, we developed a sizeable embodied carbon database of over 600 projects. This comprehensive database gave us the opportunity to engage in several collaborations with the goal of identifying benchmarks for embodied carbon in structures. We collaborated with the Massachusetts Institute of Technology and with the Carbon Leadership Forum. These collaborations fed into the CLF Embodied Carbon Benchmark Study and to the initiation of the Structural Engineers 2050 Challenge. After sending our embodied carbon report to the AIA year after year for a program that was focused on operational energy use, I was very excited to help start a new commitment that was tailor-made for structural engineers. We need the data from other firms like us to make our own data more relevant to the entire field.

Bringing the Industry Along

As a sustainability professional, I enjoy speaking with the structural engineers at Thornton Tomasetti who are passionate about embodied carbon because they see it as their big opportunity to be sustainable design leaders and to put a stake in climate change. The Structural Engineers 2050 Commitment (SE 2050) arose out of our earlier work to develop the Challenge with CLF, and it is a program meant to inspire other firms with structural engineering to embrace embodied carbon as their big opportunity. As an inaugural signatory of the SE 2050 Commitment, and as a member of the Structural Engineering Institute’s working group on SE 2050, we hope our story can encourage other firms to start measuring the embodied carbon in their projects and reporting to a central database.

Thornton Tomasetti is providing structural engineering services for the first phase of Amazon’s second headquarters in Arlington, Virginia.

Thornton Tomasetti is providing structural engineering services for the first phase of Amazon’s second headquarters in Arlington, Virginia. Photo credit: ZGF

The SE 2050 is based on the AIA 2030 model, and it asks its members to annually measure and report on the embodied carbon in projects and to develop an Embodied Carbon Action Plan (ECAP). The process of developing the ECAP has itself been very rewarding, as we engaged many different people from diverse practices and offices at the firm in its development. The process itself created buy-in and interest in the reduction of embodied carbon. We followed the development of the ECAP with a firm-wide embodied carbon summit and follow-up internal seminars to assist in putting the ideas in the plan into practice.

Our ECAP outlines our firm’s goals and targets for embodied carbon, and is available on-line on the SE 2050 website. Our reduction goals are based on what we’ve learned about opportunities for reduction from our R&D project. They include achieving a 25 percent reduction by the end of 2025 and a 40 percent reduction by the end of 2030 in average embodied carbon for our structural frames from our 2019 benchmark. We are accountable to meeting these targets as members of SE 2050, but also because they are written into our Corporate Responsibility Plan. Our seven corporate responsibility goals guide the company on our “ESG,” or environmental, social and governance performance. One of these seven goals is to lead the industry in the reduction of embodied carbon in structures. Each year, we measure progress towards our corporate responsibility goals and publish a corporate responsibility report, which offers transparency on our progress, and we share this report with our clients and colleagues who help keep us true to our commitments.

From Research to Practice

Engaging in embodied carbon R&D built up our knowledge in embodied carbon assessments and reduction strategies, and we are able to bring that expertise to our projects. We also develop tools informed by our experience. In January 2020, we released via open source an embodied carbon measurement tool, Beacon, which was pre-dated by our internal embodied carbon calculator tool.

Using our tools and accumulated knowledge, we’ve worked on a number of interesting projects. Here are a few:

  • Using Thornton Tomasetti’s embodied carbon calculator and comparing the numbers to industry benchmarks from the London Energy Transformation Initiative (LETI), we found that our Hobhouse project was delivered ahead of the proposed 2020 targets for embodied carbon. The challenge for this London project in the midst of Trafalgar Square was to re-use as much of the historic structure as possible as it had protected status. The design team and client agreed to the goal of developing a low-embodied-carbon building by combining material retention with efficient design. The strategies used included avoiding the use of secondary steelwork by using prefabricated structurally insulated panels and using concrete with 60- 80 percent of cement replacement.
  • As structural engineer for Metropolitan Park, the first phase of Amazon’s second headquarters, we were tasked with making major reductions in the project’s embodied carbon. In this project, we used Beacon to optimize early big-picture decisions. Later, we worked with the project team to develop specifications with targets and guidance to help concrete contractors craft lower-carbon mixes.
  • A growing area for us has been in the use of mass timber instead of carbon-intensive steel or concrete. We’re inventing new technology tools to rapidly evaluate timber framing systems for strength, serviceability and embodied carbon. Our work in performance-based fire engineering is showing that mass-timber structures are safe and durable. And, we’re designing mass timber buildings like the world’s tallest timber tower, under construction in Milwaukee, Wisconsin, to a hospital in Frisco, Texas, and a pavilion in Dubai.

Thornton Tomasetti’s project for the Texas Health Hospital uses timber instead of steel or concrete as a key part of a more resilient future. When managed sustainably, timber can be a renewable resource that substantially reduces the embodied carbon in a building’s design. Photo credit: ©Tom Harris 2017

Where Do We Go From Here?

Our interest in embodied carbon continues and grows, and to meet that need we launched an embodied carbon community of practice – our communities of practice cultivate innovation by encouraging employees with similar interests to collaborate, share knowledge, and develop best practices. With over 100 employees engaged in the group, we accomplish our goals through working groups focused on education; materials; measurement; and industry leadership. As co-leader of this community, I’m proud about what we’ve been able to accomplish. Our projects include: the development of embodied carbon specifications for concrete; the building of a comprehensive on-line resource library that includes our case studies and slides; the development of a guide to embodied carbon assessments; research on our data set with University of Washington students; and the initiation of a new CLF Regional Hub in Los Angeles.

At Thornton Tomasetti we’ll continue to develop our own expertise and experience with embodied carbon reduction, while hoping what we are doing is inspiring others in the industry so that together we can make real change happen. We’re sticking with embodied carbon because we believe that our best opportunity to demonstrate positive environmental and social impact is in the areas where we can have the greatest contribution based on our knowledge and talent and where we can apply our ingenuity.

Amy Hatten

Amy Hattan