Understanding Embodied Carbon & Affecting Change

By Luke Carothers

A major component of achieving carbon neutrality lies in identifying areas of our society that contribute the most to emissions.  It is no secret that buildings make up a significant portion of yearly emissions, and this recognition has led to industry-wide efforts to find new ways to decarbonize and retrofit buildings.  One of the companies at the forefront of efforts to achieve carbon neutrality is Arup.  Their recent efforts within this space have included projects such as measuring the US’ progress in decarbonizing the commercial real estate sector, identifying carbon emissions savings through office-to-residential conversions, and advancing sustainable building materials.

Linda Toth is an Associate in Arup’s Washington DC office, working with the Climate and Sustainability team. Her educational background is in Architecture and renewable energy, and her role at Arup allows her to do something she very much enjoys: solving technical challenges. Toth points out that, while Arup thinks about the way their company operates and the ensuing carbon footprint, they have a tremendous opportunity to make a wider impact through the projects they work on. Toth says that this understanding led them to begin measuring what is known as a “company handprint.”  Part of this came with a commitment to measuring the embodied carbon of all of their projects within the buildings sector. Toth says this demonstrates a commitment to pushing the market forward while also pushing their own teams to understand the impact of embodied carbon.  By understanding their own impact on carbon emissions, Toth notes that Arup’s teams are able to speak more intelligently about applicable design solutions for  the issue while working across disciplines to find the best solution to influence positive outcomes.

Currently, regulations on embodied carbon and building codes vary from place to place. Farnsworth notes that while incentives are a good start for pushing the conversation forward, local regulations need to be updated to both allow positive change and encourage it.  A good illustration of the effect of code and regulation on sustainability is a project located in Washington DC: 80 M Street SE.  Opened in September 2022, 80 M was the first commercial office building in Washington DC to feature a vertical extension constructed of mass timber as well as the first high-rise overbuild timber structure in North America.  The unique 108,000 square foot addition was designed by Arup along with Hickok Cole and adds three full floors to the previously existing seven story concrete building.  While 80 M now crowns Washington DC’s skyline with its sustainable biophilic design, Toth says the process of getting it designed and built required considerable passion from the design and contracting teams combined with perhaps a little bit of luck.

Crucial to early momentum for the 80 M project, Toth highlights the willingness of the contractor to explore a newer to market building material at that time—working diligently to price and source materials, adapt the construction schedule and process, and collaborating with structural engineers—as the start of what would become a groundbreaking process.  Also crucial to this process was gaining regulatory approval for the building’s exposed mass timber elements.  The version of the International Building Code (IBC) adopted in most US jurisdictions including Washington DC caps the height of timber buildings at 85-feet, a height they hoped to exceed with the 80 M project and limits the amount of timber that can remain exposed within the interior.  To gain approval for the project, Arup’s integrated team of mass timber experts, working closely with Hickok Cole and the DC permitting agency, had to demonstrate that the proposed solutions fulfilled current fire and life safety code requirements as well as aligned with the standards of the 2021 IBC to allow mass timber buildings of up to 12-stories.

When it comes to addressing carbon concerns, there has been considerable progress in the operational carbon space as owners become more aware of how carbon emissions are connected to energy bills. David Farnsworth, Arup’s Americas Property Leader, believes that much of the progress in the Operational Carbon space, at least within their primary markets, has been a result of cities regulating operational carbon on projects, which has resulted in clients being active in mitigating operational carbon. Farnsworth is a Principal and Structural Engineer at Arup’s New York office, and has been a part of Arup’s team for over 25 years. Farnsworth began his career with Arup on the infrastructure side, working on bridge designs and big infrastructure projects.  He switched to working on buildings around 20 years ago, quickly progressing to working on tall buildings all over the world.  Farnsworth currently leads Arup’s Property Market business, which encompasses commercial office, residential, hotel, and retail spaces.  While there has been significant progress within the space of Operational Carbon, Farnsworth believes that there is still progress that needs to be made from the perspective of Embodied Carbon, particularly within the United States.

Both before and after the successful design and completion of the 80 M project, Arup has been involved in advocating for mass timber as a sustainable design material while actively pushing it throughout the region.  Their teams have been involved with not only the design of mass timber structures, but also around the research and testing that enables the expansion of building codes.  However, while mass timber is a great sustainable option that provides an aesthetic appeal that helps attract clients to its use, Farnsworth points out that it isn’t the ultimate solution for all buildings.  He believes there also needs to be significant progress in using other materials more sustainably, such as steel and concrete.  

Pointing to an abundance of steel from scrap and recycled sources throughout the developed world, recycled steel could be a strong sustainable building material as we develop things like electric arc furnaces powered by renewable energy resources.  However, when it comes to developing sustainable building materials for the future, Farnsworth believes concrete should be the highest priority.  This means a focus on things like developing low carbon concrete and working to get higher cement replacement ratios built into owner’s requirements.  Farnsworth points to a number of different client organizations, particularly in the federal sector, that still have high cement content requirements, and that this needs to change as solutions around low carbon concrete are studied and deployed.  Even industry standard solutions, which many engineers just take for granted, should be questioned.  For example, lightweight concrete on metal decks is a standard solution in the US for office projects given perceived benefits for fire rating and reduced weight.  Most engineers don’t yet realize that lightweight concrete has a significantly higher carbon footprint than normal weight concrete and more optimal solutions are possible from a carbon perspective.  Arup has recently focused efforts on studies to assess the impact on embodied carbon of various slabs on metal deck options to challenge the status quo once carbon is part of the equation.

While there is an almost unanimous sentiment across the AEC industry that we should be pushing forward in all aspects of sustainability—as well as no shortage of carbon neutrality agreements and pledges—there is, perhaps understandably, little consensus on how change should be best enacted.  Change is often a piecemeal process, but the act of committing to enacting it is the first step in solving the challenges of the future.  As the AEC industry looks to continue shaping the built environment in a way that answers the challenges of climate change, firms like Arup are exemplary of this commitment to change.