Report gauges building codes’ impact on embodied carbon in project specs

Sources: New Buildings Institute, Portland, Ore.; CP staff

The most recent New Buildings Institute (NBI) report offers language to incorporate embodied carbon requirements in codes, and explains the need for jurisdictions to address such criteria for materials or products with the highest carbon dioxide emissions factors. “Lifecycle GHG Impacts in Building Codes” presents potential CO₂ benchmarks or thresholds for ready mixed concrete, rebar and structural steel based on extensive Environmental Product Declaration (EPD) data mining.

NBI researchers contend that code inclusion of limits for global warming potential (GWP)—a principal EPD data point reflecting the CO₂ emissions load per product or material unit—can impact more of the building lifecycle by addressing upfront embodied carbon, as well as construction and operational emissions. They consolidate GWP data on six commercial concrete mixes of 2,500 psi to 6,500-plus psi design strength in “Lifecycle GHG Impacts,” tapping industry-wide EPD or thousands of individual plant declarations from producers across 26 states. Researchers compare that data to GWP benchmarks in Marin County, Calif., home to the first local building code in the U.S. to stipulate low-carbon concrete, expressed as CO₂ equivalent/cubic yard, for certain applications.

The Institute report works to address the current lack of understanding of what regulation on building lifecycle emissions would look like in a U.S. base building code. Code officials can adopt language to target GWP limits for specific materials or products, starting with EPD reporting requirements and potentially moving to a whole life carbon approach with whole building lifecycle analysis.