Last month we explored a topic of growing importance, embodied carbon in buildings (the carbon footprint of building materials and construction). As we reduce operational carbon emissions, embodied carbon accounts for an increasing share of the total life cycle carbon footprint of buildings. Due to the “time-value-of carbon,” emissions reductions today in embodied carbon are more critical than ever in averting the climate crisis than operational emissions avoided in the future.
Embodied carbon and other product vitals
Unfortunately, evaluating alternatives and making informed design decisions to reduced embodied carbon in buildings is easier said than done. Thankfully, there are an increasing number of resources and tools available to building professionals to support sound decision making while trying to reduce embodied carbon. These include Environmental Product Declarations (EPDs) for the impacts of individual materials, and whole building life cycle assessment (LCA) tools that look at the combined impacts of the entire assembly. This month, we will take a deep dive into EPDs, followed next month with a close look at LCA tools and applications.
What is an EPD?
An EPD is a holistic summary of the environmental impacts of a material, including but not limited to water, energy and atmosphere. They can be a primary source for information on the embodied carbon of particular materials, allowing side-by-side comparisons, but this is not the only attribute found on them. An EPD includes:
- Global warming potential (CO2 emissions)
- Ozone potential and creation
- Water use and water quality impacts
- Energy and material resource use at each stage of product life cycle
- Recycled content
- Waste outputs
What Can We Learn From an EPD?
We learned from the earliest version of LEED to look at single attributes of materials, like recycled content, regional sourcing and VOC emissions. While this is helpful, EPDs offer a more comprehensive approach to sustainable material evaluation, especially when considering the inevitable tradeoffs in impacts. For example, a material like composite wood might have a high recycled content and low embodied carbon, but also have a high atmospheric pollution potential. There is a common misconception that an EPD reports acceptable or allowable thresholds for each parameter. This is not true, as they are purely informative documents and not meant as a compliance check against any established standards.
However, EPDs do reveal data useful in decision making, such as differences in manufacturing processes. Two recycled-content steel products may be similar in constituents, but if one is manufactured using an electric arc furnace (EAF, typical of domestic U.S. steel) and the other with a basic oxygen furnace (BOF, typical of some imported steel), the EAF-produced steel will have a much lower carbon footprint. Conversely, EPDs do not factor in transportation to the project site. Two metal products with similar constituents and manufacturing processes might have nearly identical impacts identified on their EPDs, but if one must travel a long distance via carbon intensive transport, it will have a more significant impact on the building’s embodied carbon, which is not reflected in the EPD.
EPDs can provide useful information to improve the accuracy of whole building LCA, because they provide product and manufacturing facility specific data on raw materials sourcing and transportation, manufacturing process, recycling, etc. However, there are still limitations. While the number of available EPDs is increasing rapidly, there is still only a fraction of all building materials covered in currently available declarations. Additionally, while product-specific and manufacturing facility-specific EPDs exist for some products, in other cases the only available data is from industry-wide EPDs, which are useful, but limited in their accuracy (due to variations throughout the industry that change the impact). As the critical mass of EPDs grows, we will better be able to make material selections based on side-by-side comparisons of impacts for all major building materials and finishes.
Where Does the Information Come From?
EPDs are intended to be consistent and reliable sources of information on the environmental impacts of materials. To maintain this credibility, a standardized process was established for performing product LCA, and verifying and certifying the results. This starts with product category rules, which standardize the requirements for how the LCA must be performed for all similar products within a category (e.g., metals). The LCA analysis and verification process follows ISO 14040, 14044 and 14025 globally, which makes most EPDs comparable. While EPDs are technical documents, the information is self-explanatory and accessible to most people, so material science expertise is not required to read one.
Where Can I Find EPDs?
The first and best way to access EPDs is to contact vendors or manufacturers. There are also several useful material databases with information on sustainable materials, including EPDs. These include: Origin, mindful MATERIALS, Ecomedes and UL SPOT.
With credible predications of the disastrous consequences of the climate crisis looming, consideration of embodied carbon in buildings is here to stay and will only increase in importance. At the national conference in June, the AIA passed Resolution 19-11, supporting urgent and sustained action to decarbonize buildings. Environmental Product Declarations are a reliable source of information on embodied carbon and other parameters to inform material selection in support of this goal. Architects, designers, engineers and contractors should become familiar with them, and encourage greater participation from manufacturers in developing and sharing them. Informed decisions lead to positive climate outcomes.
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Alan Scott, FAIA, LEED Fellow, LEED AP BD+C, O+M, WELL AP, CEM, is an architect with over 30 years of experience in sustainable building design. He is a senior associate with WSP in Portland, Ore. Mohammad Hossein Abbasi, Assoc. AIA, CPHC, LEED AP BD+C, is a building performance analyst with WSP in Chicago, helping clients make a better decision on the energy use, health and environmental impact of their buildings. To learn more, visit www.wsp.com/en-US/services/built-ecology and follow Scott on Twitter @alanscott_faia.