ATLANTA - Fan power limitation requirements for complex HVAC systems, such as those in hospitals and laboratories, would be improved under a proposed change to the American Society of Heating, Refrigerating and Air-Conditioning Engineers' (ASHRAE's) energy standard.

Eight proposed addenda to ANSI/ASHRAE/IESNA Standard 90.1-2004, "Energy Standard for Buildings Except Low-Rise Residential Buildings," are open for public comment until May 1.

Included is addendum ac, which would expand application coverage to address complex mechanical systems.

"The standard would more effectively address static pressure associated with complex HVAC systems requiring specialized equipment in return air or exhaust air systems, such as those in hospitals," said Larry Kouma, who heads the group that oversaw the proposed addendum. "Appropriate allowances for discharge and return air flow treatment equipment would be allowed, enabling a clear avenue for these systems to demonstrate compliance using the prescriptive compliance methods of the standard. Or, if required, users can still use the standard's energy cost budget method."

The addendum is also designed to improve compliance consistency and strengthen stringency for simple systems with an easy-to-use format and structure.

Other proposed addenda open for comment until May 1 are:

  • Addendum aa which adds definitions for lighting related terms;

  • Addendum ab which clarifies which sections should be referenced in Section 11 and Appendix G;

  • Addendum ae which changes Section 11 and Appendix G to clarify the way lighting power is to be modeled;

  • Addendum ai which revises the lighting power requirements to eliminate confusion;

  • Addendum aj which adds the ASTM test method E 1980 – Standard Practice for Calculating Solar Reflectance Index of Horizontal and Low Sloped Opaque Surfaces;

  • Addendum al which clarifies the terminology for metal building roofs and the required assembly U-factors for such roofs; and

  • Addendum am which allows minimum variable air volume turndown to be limited by the minimum ventilation requirement for a zone.

    To obtain drafts of or comment on these proposed addenda, visit

    Publication date: 04/17/2006