A proposed addendum adding an optional third compliance path to ANSI/ASHRAE/IES Standard 90.1-2010, Energy Standard for Buildings Except Low-Rise Residential Buildings, will be open for public review until Nov. 26.

Under Addendum bm, a new building would comply by showing a performance improvement of at least 45 percent over a baseline design calculated in accordance with Appendix G. Additionally, Addendum bm would make the baseline consistent with the prescriptive requirements of Standard 90.1-2004.

The paths currently in the standard—the Energy Cost Budget Method and the Performance Rating Method—can lead to different modeling protocols for different functions, Michael Rosenberg, a member of the Standard 90.1 committee, explained. All require slightly different rules. A single project could require two or more 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, such as the U.S. Green Building Council’s (USGBC’s) LEED green-building certification program; ANSI/ASHRAE/USGBC/IES Standard 189.1-2011, Standard for the Design of High-Performance, Green Buildings Except Low-Rise Residential Buildings; and federal tax-incentive programs. Each simply chooses its 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,” Rosenberg 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.”

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