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decisions. WBLCAs assess all stages of a building’s life cycle in their calculation, including the product stage (Modules A1–A3), construction stage (Modules A4–A5), use stage (Modules B1– B7), end-of-life stage (Modules C1–C4) and the benefits and loads beyond the system boundary stage (Modules D). [109]

The baseline and proposed buildings must be of comparable size, function, orientation, and operating energy performance as defined in EAp2: Minimum Energy Efficiency . The service life of the baseline and proposed buildings must be the same and at least 60 years to fully account for maintenance and replacement. Baseline assumptions must be based on standard design and material selection for the project location and building type. Use the same life cycle assessment software tools and data sets to evaluate both the baseline building and the proposed building and report all listed impact categories. Data sets must be compliant with ISO 14044 [110] .

When developing a baseline model (also known as reference building), use recommended modeling software and generate a model that is comparable in size, function, orientation, building geometry, structural and thermal performance. If a team iterates early in design and makes design changes to create a lower embodied carbon design, they may use their early design iteration as a baseline given that it aligns with the comparative requirements listed above. A team may also make a copy of their proposed design which includes low embodied carbon implementation and replace materials with the regional commonly used materials. For further guidance on developing a baseline model, see the following resources:

• Whole Building Life Cycle Assessment: Reference Building Structure and Strategies [111]

• National Guidelines for whole-building life cycle assessment [112]

• City of Vancouver Embodied Carbon Guidelines [113]

Option 2: EPD Analysis

EPDs are a standardized way of communicating the environmental impacts associated with a product’s raw material extraction, energy use, chemical makeup, waste generation, and air, soil and water emissions, among other endpoints. Project teams who analyze EPDs can more

109 “Measuring Embodied Carbon” (Figure 1), Carbon Leadership Forum (CLF), (2023), https://carbonleadershipforum.org/toolkit-2- measuring/. 110 “ISO 14040”, ISO, (2006), https://www.iso.org/standard/37456.html. 111 “Whole Building Life Cycle Assessment: Reference Building Structure and Strategies”, American Society of Civil Engineers (ASCE), (2018), https://sp360.asce.org/personifyebusiness/Merchandise/Product-Details/productId/239605051. 112 Bowick, Matthew, O’Connor, Jennifer; et al. “National guidelines for whole-building life cycle assessment”, National Research Council Canada, https://doi.org/10.4224/40002740. 113 “Embodied Carbon Guidelines”, City of Vancouver, (October 2023), https://vancouver.ca/files/cov/embodied-carbonguidelines.pdf.

U.S. Green Building Council LEED v5 Reference Guide for Building Design and Construction, April 2025 Launch Edition 415