Hello,
Athena does not provide data for stages B1, B3, and B5. Based on the NRC guidelines, when a software tool omits certain stages, it is acceptable to assume that the combined impact of stages B1–B5 equals 10% of the impacts from stages A1–A3. To clarify: Should we disregard the individual B-stage impacts that Athena does provide, and instead apply the 10% assumption across the entire B stage? Or, should we keep the B-stage impacts Athena calculates and add the 10% of A1–A3 impacts only to account for the missing stages (B1, B3, and B5)?
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My understanding is that the B-stage results from Athena are sufficient to show compliance with the NRC National wbLCA Practitioner’s Guide (2024). This 10% number was generated based on the aggregated results of many City of Vancouver Rezoning and Building Permit wbLCA submissions, supplemented with other data. Therefore, the B-stage results from Athena will be more material specific, and likely more representative.
Note that you’ve mentioned the National Guidelines (2022), which don’t contain the 10% factors you reference.
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