ASHRAE Standard 90.1 introduces new energy-saving requirement

The 2025 edition of American National Standards Institute/ASHRAE/Illuminating Engineering Society Standard 90.1, Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings, has been published and includes an important new requirement for hospitals and other health care facilities.

Addendum bh to the standard’s 2022 edition was approved in 2025 and is now incorporated into the published 2025 standard along with several other addenda that have passed since 2022. Addendum bh required health care facilities to implement unoccupied setbacks in certain clinical spaces. This means reducing ventilation or adjusting temperature settings when specific spaces are not in use. The change will have a meaningful impact on energy use and carbon reduction across health care environments. Health care facilities located in states that decide to adopt the 2025 version of the standard should be aware of this important change.

This update in the new edition of Standard 90.1 supports a larger direction set by ASHRAE to achieve net zero carbon and net zero energy in new buildings by 2031.  As part of this effort, the committee introduced several addenda to the 2022 edition focused on energy efficiency and decarbonization. Addendum bh  was one of the key updates affecting health care facilities and has now been incorporated into the 2025 edition.

To ensure patient safety and clinical appropriateness, the committee for Standard 90.1 limited the mandatory setback requirement to spaces with high air change rates that are already permitted to use unoccupied setback under ANSI/ASHRAE/American Society for Health Care Engineering Standard 170-2025, Ventilation of Health Care Facilities. These spaces have been determined to be safe for reduced air changes when they are unoccupied. They include:

• Operating rooms
• Surgical cystoscopy rooms
• Procedure rooms
• Class 2 and Class 3 imaging rooms

Energy and carbon analyses were conducted to understand the impact of this requirement. The results were very positive:

• Energy savings were favorable and showed a clear payback for the operational effort required.
• Carbon reduction benefits were even stronger and offered meaningful long-term environmental and economic value.

Maintaining clinical readiness in turndown mode

As hospitals implement turndown strategies to reduce energy usage during unoccupied periods, it is important to maintain clinical readiness. Recognizing this,  addendum bh to Standard 90.1-2022 included a targeted exception to the unoccupied turndown requirement for certain health care spaces.

To support rapid activation for emergency patient care, facilities may designate the greater of two zones or 25% of zones for each space type to remain configured as continuously occupied. This allowance enables facilities to respond quickly without compromising patient safety or operational readiness. However, this exception does not eliminate the expectation to design for energy efficiency or system flexibility. Zones designated for continuous occupied operation must still be designed with full turndown capability in new construction or additions.

Managing compliance with conflicting requirements

Health care facilities often must navigate difficult situations where different standards governing ventilation systems are not fully aligned. This is particularly common where state and local jurisdictions have adopted standards that conflict with ANSI/ASHRAE/ASHE Standard 170-2008, Ventilation of Health Care Facilities, which is still being enforced by the Center for Medicare & Medicaid Services Conditions of Participation.

Where one authority having jurisdiction (AHJ) has not yet adopted a version of Standard 170 that permits ventilation turndown, facilities may still plan for future flexibility without violating newer requirements adopted by different AHJs. In these cases, addendum bh included an exception requiring ventilation systems to be capable of turndown, but they do not need to be actively configured to operate in turndown mode. This distinction allows hospitals to maintain compliance with existing CoPs while designing systems that can adapt as standards evolve, balancing patient safety, operational readiness and long‑term energy performance.

Overall, addendum bh provided a practical and evidence-based approach to reducing energy consumption in health care facilities. It built upon strategies already permitted by recent editions of Standard 170 and addressed real-world challenges like clinical readiness and conflicting standards. The change was intended to support both cost savings and significant carbon reduction while maintaining safe clinical operation.

Related article // How often are updated ASHRAE standards released?

ASHRAE standards are updated on a continuous basis. Committees for each standard make updates by amending the last printed edition. The previous edition of American National Standards Institute/ASHRAE/Illuminating Engineering Society Standard 90.1, Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings was printed in 2022, and several addenda have been passed since then. ASHRAE has just published the 2025 edition, which includes all approved addenda since 2022. 

Leah Hummel, AIA, CHFM, SASHE, CHC, CHOP, is senior associate director of ASHE Regulatory Affairs.