When it comes to reducing the carbon footprint of your projects, getting exactly what you specify is essential. Luckily, there's a powerful new resource available to help you secure low embodied carbon structural steel--consistently and confidently.
The American Institute of Steel Construction (AISC) has released Specification Strategies for Embodied Carbon Reduction, a concise, authoritative guide available at aisc.org/sustainability-toolbox. It distills the latest and most relevant approaches for procuring low embodied carbon structural steel into clear, actionable specification pathways. The document presents six strategies supported by expert commentary, comparative ratings, and ready-to-use specification language.
This publication was a collaborative effort between AISC's own Sustainability Committee, the Resources Subgroup of the SEI Sustainability Committee, the Specification Working Group of the NCSEA National Sustainable Design Committee, and a consulting architect specializing in specification writing.
If you're newer to the topic, embodied carbon refers to the greenhouse gas (GHG) emissions associated with creating, transporting, using, and ultimately disposing of those materials over the entire life cycle of a building. For steel, the biggest emissions impacts occur when raw iron ore is processed into steel. Fortunately, the majority of U.S.hot-rolled structural steel is produced from recycled steel content (scrap metal), generating little additional emissions. Understanding embodied carbon and modern steel production processes empowers designers to make informed, climate-forward decisions without compromising structural performance.
Keep reading for descriptions of each strategy and its intended use, and learn more at aisc.org/sustainability.
Strategy #1: Request Environmental Product Declaration (EPD) Disclosure
AISC recommends all construction specifications include the requirement for EPD disclosure. It is easily implemented and unlikely to have a substantive impact on either project cost or project schedule. This is an easy way to ensure that you're working with vendors (regardless of material) who are just as committed to sustainability as you are, and when it's time to add up credits for various green building rating systems, the documentation you need will be right at your fingertips. Requiring EPDs has the added benefit of underscoring that the market cares about having current, transparent, and accurate documentation.
Strategy #2: Require Fabricator's Sustainability Practices Documentation
AISC recommends that all steel construction specifications require documentation of the fabricator's sustainability practices. Although steel fabrication makes up only a small fraction of the total cradle-to-gate footprint, it's worth engaging with sustainable fabricators to promote lean and sustainable practices. Precisely how they run their operations, from material procurement all the way to the jobsite, makes a difference. Requiring documentation about a fabricator's sustainability practices is another way of ensuring that your entire project team is committed to the same goals.
Here's a shortcut: AISC offers a sustainability partner program specifically for steel fabricators. The program provides best practices and helps them streamline their operations and the resulting environmental impact. Any fabricator participating in the program has already met the requirements laid out in this specification language. You can find a list of them at aisc.org/partnerprogram.
Strategy #3: Choose Domestic Sourcing
Simply choosing domestic steel can cut your project's environmental footprint in half. The American structural steel industry's average embodied carbon intensity is way ahead of the global average (by around 40% for hot-rolled sections, in fact), and buying steel made right here eliminates the pollution associated with transcontinental transportation.
While it's possible for some foreign sources to have carbon intensities generally on par with the U.S., care must be taken to assess the environmental impacts of global transportation and to evaluate whether foreign carbon intensity reporting meets the same U.S. standard of quality. Regardless, foreign-sourced steel must always include certification from a domestic importer that material properties are correct and verifiable.
Strategy #4: Choose Electric Arc Furnace (EAF) Sourcing
Globally, EAF steelmaking is on average 75% less carbon intensive than blast furnace (BF)/ basic oxygen furnace (BOF) processes, due to the fact that using recycled scrap as feedstock for new steel is considered to have nearly no environmental impact.
How your project's steel is made has a huge impact on its sustainability. There are two ways to do it. In the U.S., most structural steel produced--including all wide-flange sections--is made with scrap and electricity in an electric arc furnace. Domestic EAF wide-flange steel has recycled content levels of 90% or more. The BOF process uses older steel-making methods, relying on iron ore as the primary feedstock.
With the exception of domestic wide-flange, which is always made in an EAF, the marketplace offers both EAF- and BOF-produced versions of many steel products. This is where your specification can make a huge difference. For products like steel plate that have not been substantially re-formed between the mill and the jobsite, verifying the production process is straightforward. Manufacturers of products like open-web steel joists, deck, and hollow structural sections (HSS) should investigate and disclose how their source material is made.
Strategy #5: Set Global Warming Potential (GWP) Limits at 125%
Published GWP values are an indicator of a steel product's embodied carbon.
GWP limits are commonly established at industry average levels, but AISC suggests setting limits at 125% of industry average levels.
A table within this section of the specification strategy document provides cradle-to-mill-gate and cradle-to-manufacturer-gate GWP limits, as appropriate, and assumes a 125% level. The impact of individual downstream processes (like custom bending/rolling, castellation, fabrication, and coatings) are explicitly excluded. Because they are relatively small and vary depending on the architectural design, excluding them allows the limit to focus on the largest and most comparable emissions source. For more, download Buy Clean Guidance for Structural Steel Products from aisc.org/buyclean.
Strategy #6: Don't Use Recycled Content as a Carbon Measure
There is a correlation between higher recycled content levels and lower embodied carbon intensity, but AISC does not suggest using one as a proxy for the other, as mill-reported values reflect annual averages rather than the specific steel delivered to a project.
These documents remain helpful primarily because some green building programs continue to request them, but they should not be viewed as a measure of embodied carbon. More accurate assessments come from product-specific EPDs and reported GWP values, which provide a clearer picture of steel's environmental impact.
Conclusion
For each strategy you adopt from Specification Strategies for Structural Steel Embodied Carbon Reduction, you can have the confidence that your project's specification is now contributing to a growing wave of signals that tells the steel industry that embodied carbon reduction is a valued performance metric, which incentivizes broad steelmaking decarbonization. Companies exist to compete for your business and deliver products the market wants. You are the market, it's your job to signal your values, and AISC's Specification Strategies for Structural Steel Embodied Carbon Reduction empowers you to do so. Explore this resource and more at aisc.org/sustainability-toolbox.
Max Puchtel, SE, PE ([email protected]) is the director of sustainability and government relations at the American Institute of Steel Construction.
For more on the sustainability of structural steel, visit aisc.org/sustainability.