Embodied Carbon Calculations Are Simple, Right? Not So Fast!

by Andrew Himes

Several years ago, the concept of embodied carbon was new to me, and I had a simplified notion of how we might go about reducing carbon emissions from building materials and construction. In 2012, the CLF had developed and published version 1.0 of a North American Product Category Rule (PCR) for concrete, the most widely used building material in the world. That PCR laid the basis for companies to produce Environmental Product Declarations (EPDs), reporting the carbon impacts for various recipes of ready-mix concrete. I imagined that might be all it would take to transform the industry, right? Just get every material manufacturer to publish EPDs, tens of thousands of them, and get every designer to use tools like the EC3 tool to calculate, compare, and reduce a project’s carbon impact, and you have most of the solution in hand.

As we’ve learned, however, reality is not so simple.

Lots and lots of diverse players need to change their behavior in significant ways. Tools and carbon reporting pathways need to be available to help building designers make intelligent decisions leading to the procurement of low-carbon materials. Policymakers need to be educated and supported in developing rules and guidelines to help transform the markets for materials. Real-estate developers and investors need to help drive demand for low-carbon solutions. Individual firms and practitioners need to align with certification programs such as LEED, Passive House, and the Living Building Challenge, and join industry-wide movements such as AIA 2030, SE 2050, and MEP 2040.

Finally, understanding the relationship between operational carbon and embodied carbon—the carbon balance—requires a holistic understanding of the entire lifetime of a material, building, or project with the aid of the discipline of life cycle assessment (LCA). As CLF’s report Advancing the LCA Ecosystem said in the fall of 2023, “The effectiveness of policies in reducing embodied carbon relies on the health of the underlying LCA ecosystem—the standards, guidelines, data sources, tools, and actors/organizations that constitute the interdependent building blocks of LCA—to create consistent, reliable estimates of embodied carbon to report and benchmark products and projects.”

Even with all the progress we’ve made over the past few years, we still have much to learn. A group of building systems engineers who are part of the MEP 2040 Commitment recently concluded that the most significant component of the carbon footprint of HVAC systems might not be individual products and systems, but rather the sheer volume of infrastructure required for such a system—the miles of piping and wiring and ducting that are part of any sizable building. So, for example, ground-source heat pumps have been touted as a highly efficient, clean, and sustainable HVAC solution compared with the carbon pollution associated with gas furnaces. However, when you account for the embodied carbon footprint of a geothermal well, the carbon advantage of a ground-source heat pump becomes less certain.

All of this highlights the importance of what we do at the Carbon Leadership Forum: extending the understanding and practice of whole building LCA to include all the components of a building and every type of building; creating and maintaining the material baselines used by tool developers and designers alike to set benchmarks and targets for carbon reduction; creating toolkits and models to educate and support policymakers at every level of government; and deepening collaboration to enable collective action across the industry.

Together with you, our partners and collaborators, we’re building a movement to transform one of the largest industries on the planet.