Embodied carbon: apples to apples

by Jennifer Hardy, AIA

How can we integrate life-cycle thinking to inform and influence material decisions when they are initially visualized?

Melanie Silver, AIA, LEED AP BD+C
Silver works with design teams to meet rigorous sustainability targets through data-driven investigation. She manages the building performance
simulation responsibilities in the Building Science Group and leads Payette’s Materials Research Team, responsible for developing and implementing
material policy. She represents Payette regularly at client meetings and in public presentations. Silver educates the design team on issues relevant to building performance, while understanding which elements are critical to the building’s design or program.

Rebecca McGee Sturgeon, Assoc. AIA
At Payette, McGee Sturgeon primarily works within the firm’s science practice, focusing on renovation and adaptive reuse. In addition to her project work, McGee Sturgeon is a member of the Materials Research Team and leads the LCA research. Prior to joining Payette, she worked as an architectural R&D designer in building materials and systems assembly design at Saint-Gobain NRDC and before that as a senior designer and art director for Qorvis MSLGroup, a communications agency in Washington, D.C.

Research at Payette often starts with a simple question and desire to make more informed choices on key design decisions. Usually, our questions are broad, and investigation quickly leads us down multiple rabbit holes of factors upon factors that impact the evaluation of any one question. We, like so many others, are interested to make carbon reduction an integral part of our design process, so we start by identifying a target that maximizes impact toward our goal. This target lays the groundwork for further development, refinement and knowledge advancement to embed a new way of thinking into the culture of our design process.

Jennifer Hardy (JH): What inspired the research topic?
Melanie Silver (MS): The recent reports from the IPCC have brought awareness to the urgency that embodied carbon must be addressed. Forty percent of the global carbon emissions come from the building sector. When you combine the impact of operational and embodied carbon emissions from buildings, they represent the largest single emitter of carbon. As architects and stewards of the built environment, it is our imperative to dramatically reduce this. Historically, at Payette, we have been focused on reducing operational energy, but looking at the next 10 years (which considers the time value of carbon that we must reduce carbon between now and 2030 in order to stay below 1.5°C temperature rise), the embodied carbon of new construction will far surpass the carbon needed to operate those buildings. We need to simultaneously address performance and evaluate our choice of materials in order to meet the goals of the Paris Agreement.

The building industry typically focuses on the 60-year life span of a building when performing Life Cycle Assessments (LCAs) to assess the total carbon emissions. But if we evaluate the carbon emissions of buildings over the next 10 years, toward AIA 2030 goals, the overwhelming emphasis on carbon reduction is on embodied carbon, which must be reduced with greater urgency in order to stay below 1.5°C, per IPCC. This is why Ed Mazria and Architecture 2030, which instigated the AIA 2030 Commitment, has also set an Embodied Carbon Challenge that has a forty percent reduction target stepping down towards a net-zero embodied carbon in 2050.

We were recently studying multiple facade systems for the new Pennsylvania State University College of Engineering Research & Teaching Space, West 2, when the team asked, “What if we considered the embodied carbon of these options to inform our decision?” Luckily, this newly formed research team, led by Luke Laverty, Melanie Silver, and Rebecca McGee Sturgeon, was already working on this question. They assessed our facade system options and provided a comparison chart of the different embodied-carbon impacts. We were ready to use this as one of many factors to inform our facade selection and then paused to challenge our assumptions and ask, “What is the overall net benefit of reduction in embodied carbon in the facade in context of the overall building? Are we targeting the right building component, and how much weight should we give to this information to inform our decision?”  

JH: Why target facades when attempting to reduce embodied carbon in buildings?

MS: Facades contain the second-largest percent of embodied carbon in a building (after structures), and the architect is in a position to greatly influence and reduce the impact based on the aesthetics of material choices. Facades are also highly complex, so having easy-to-access data encourages holistic, sustainable thinking.

JH: How is embodied carbon currently measured for a project?

Rebecca McGee Sturgeon (RS): There are a number of great tools and resources that currently exist and more that are being developed. Take, for example, Tally, which is a Revit plugin developed by KieranTimberlake. As you know, the design process can vary widely from one firm, or one person, to another — a lot of these tools require a certain amount of design decisions to be made or developed within a specific modeling software, like Revit, in order to provide the LCA results. At Payette, we use a range of different softwares and tools early in the development of a design. However, usually a more detailed Revit model is not in the works until later in the process. The motivation behind our research was to provide a baseline of knowledge and information that could be shared and integrated into design discussions without the need for a developed 3D model. 

As a research team, we decided to start by focusing on facade systems due to the relative impact they have on embodied carbon and the design of a project. We collected information about the assemblies we use most commonly as an office and set up the parameters for the study to make an apples-to-apples comparison, using Tally.

JH: Can you elaborate on what it means to do an apples-to-apples study?

RS: In order to be able to compare the assemblies, certain variables need to be standardized across the system boundary. We addressed this by establishing a module with the same height and width and defined the system from exterior finish to interior finish without including primary building structure.

MS: We also model each assembly so they have the same R-value; this takes out the factor of performance and operational energy. We ran parametric THERM models (2D heat-flow software) for each system to account for thermal bridging and different R-values of materials, to calibrate the thickness of insulation for each system. Then we adjusted the insulation thicknesses in our initial assembly models and are able to make apples-to-apples comparisons across the facade systems.

Once the apples-to-apples facade systems were established, the research team began evaluating them using Tally, to create an accessible database to evaluate the embodied carbon of facade systems during the early stages of design. System types evaluated thus far include masonry veneers, face-sealed assemblies, and rainscreens.

 

JH: How do you evaluate the data and interpret results?
RS: As a team, we’ve talked a lot about how to interpret and present this research. We believe Global Warming Potential is by far the most pressing impact category. However, we also feel strongly in maintaining a holistic lens. We have gathered additional research on weighting of impact categories from across the industry and are incorporating this as a lens in which to view our results — something that can be seen and evaluated in one image.

JH: I often hear people reference the carbon impact tied to the distance a material travels to the site, but how much weight should we give to that factor when selecting materials?

MS:  We found in our results that if we look at the breakdown of where the impact comes from, the majority is in the product phase, which is the process of extracting and manufacturing the material or product. The transportation has typically been a small percent of the total, which means that how the material was made is more impactful than the journey it takes to a construction site.

JH: Once the QA/QC process on the research is complete, what is next?

RS: We have an open-source web-based data-visualization tool in the works to share our results (coming this spring!) and are also beginning work on the next phase of research, which will be to evaluate other common systems and materials in the same manner. We are excited by the surge of conversation surrounding embodied carbon in the industry and are continuing to pursue the integration of life-cycle thinking into our practice.


Author Bio:Jennifer Hardy, AIA
Hardy is an architect at Payette in Boston, Mass. Hardy is an active member at the Boston Society of Architects, co-chairing the Women in Design committee, and is a 2020 Young Architect Award winner.