The proposed addendum would add a compliance path to Standard 90.1 to allow modeling in accordance with Appendix G (Performance Rating Method), provided the percentage improvement of at least 45 percent over a baseline design. In addition, this addendum proposes to make the baseline consistent with the prescriptive requirements of 90.1-2004, and it will remain that way in future versions of the standard.

The current paths in the standard — the Energy Cost Budget method and the Performance Rating Method — can lead to different modeling protocols for different functions, according to Michael Rosenberg, a member of the Standard 90.1 committee. All require slightly different rules, and a single project could require two or more different baselines.

“By allowing an additional compliance option, the standard provides more credit for integrated design resulting in energy savings such as efficient use of building mass, optimized building orientation, efficient HVACR system selection, and right sizing of HVACR equipment,” Rosenberg said.

The baseline could stay the same for beyond code programs as well, such as the U.S. Green Building Council’s (USGBC) Leadership in Energy and Environmental Design (LEED®) rating program, ANSI/ASHRAE/USGBC/IES Standard 189.1, Standard for the Design of High-Performance, Green Buildings Except Low-Rise Residential Buildings, and the federal tax incentive programs. Each simply chooses their own “percent better than” target, according to Rosenberg.

“In addition, the performance path will no longer lag behind the prescriptive path as in the past it was not possible to incorporate prescriptive changes that occurred near publication date into the performance path,” he said. “It also allows for a deliberate and consistent trend for energy reduction in each version of the standard, instead of just following the prescriptive path.”

For more information, visit www.ashrae.org/publicreviews.

Publication date: 11/12/2012