ASHRAE has announced it will split its commercial building energy standard, Standard 90.1, into two separate publications. The original standard will continue to focus on energy efficiency and energy cost requirements, while a new companion document will address operational carbon and greenhouse gas reduction. This change responds to growing demand from states, cities, and corporations for clearer pathways to lower emissions. The split formalizes a distinction that has been building for some time: energy efficiency and carbon reduction are related goals but are not identical. For contractors and engineers working in jurisdictions that adopt 90.1 as the basis for building codes, carbon-related requirements will move into an optional companion document rather than the core standard. Content from the 2025 edition's optional Addenda M and N, which addressed operational carbon, will migrate to the new publication as part of the 2028 and 2031 work plan. This structural change has direct implications for mechanical engineers and HVAC contractors working on commercial projects. It reflects a broader trend in building codes and standards toward treating energy efficiency and carbon reduction as distinct but complementary objectives, with different regulatory pathways emerging for each.
