There was a request recently for RESNET to clarify whether HERS® ratings can be conducted on a whole-building scale or whether they can be conducted only for individual dwelling units in multifamily buildings. The petitioner indicated that the absence of clarity in RESNET standards allows some rating software programs to have options for “multifamily, whole building”, or “duplex, whole building” model types. In these model types, one software energy model file is used to model an entire multifamily building which can include two to several hundred dwelling units. This has resulted in inconsistency in the market where some rating companies provide a single rating while others provide ratings only for individual dwellings. This both confuses builders, code officials and programs and results in a competitive disadvantage for companies providing ratings for individual dwelling units. RESNET Standard Development Committee 300 issued Interpretation 2016-001 effective December 15, 2016 to address this issue. The interpretation makes clear that, “For rating purposes, a multifamily building with multiple dwelling units shall have individual confirmed or sampled ratings for each dwelling unit” and that “A single whole-building Projected, Sampled or Confirmed Rating is not permitted on a multifamily building with multiple dwelling units”. The interpretation goes further to state that, “Only HERS® Ratings on dwelling units are permitted to be uploaded into the RESNET Building Registry” and that “…spaces on a multifamily property that are not dwelling units, as defined in IECC 2015, shall not receive HERS® ratings”. RESNET recognized that a single rating index for a multifamily building may be needed for code compliance or other programmatic reason so it provided “Advisory Guidance” on how that may be accomplished as an annex to the interpretation. Whole building ratings will be addressed by the proposed standard for multifamily energy ratings, (proposed Standard BSR/RESNET/ICC 305-201x), when it is complete but in the interim the “Advisory Guidance” is intended to provide for better consistency of ratings in the market. The complete Interpretation 2016-001 Multi-Family Building Ratings and the advisory guidance can be viewed on the RESNET website at Interpretation on Application of ANSI/RESNET 301-2014 to Multifamily Buildings
