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  • ANSI-RESNET Changes May Affect HERS Index Scores

    ANSi, or the American National Standards Institute is the national governing standard for home energy ratings. Over a year ago, ANSI approved he HERS (Home Energy rating System) Index as the national standard for governing home energy ratings of new and existing homes. Though HERS was created by RESNET (Residential Energy Services Network), its adoption as the national standard lends credibility to the HERS Index as a national standard for measuring home energy efficiency.

    The ANSI-approved standard is the first national standard for energy ratings and shows a growing importance of the HERS Index as a trustworthy source for homeowners and homebuyers for measuring energy efficiency, providing a consistent and uniform methodology for evaluation and labeling of energy performance.

    According to the RESNET website: “In 2013 RESNET started to improve the quality assurance standards and procedures at the request of large national production builders who were legitimately concerned about the integrity and consistency of the HERS Index Scores nationally. These builders have heavily invested in the use of the HERS Index for marketing and in HERS Raters performing energy code compliance and tax credit verifications. These efforts culminated in a set of RESNET policies that were adopted by the Board of Directors and the creation of a balanced ANSI Standard Development Committee to oversee the development of implementation standards to carry out those policies. Some of these policies target specific practices through increased validation checks in RESNET accredited HERS Software programs for reasonability. These actions were taken to clearly define the boundaries on data that HERS Raters can input into the rating software programs.

    In the past, RESNET’s standards and procedures allowed too much flexibility in the software inputs of accredited rating software programs which resulted in inconsistencies between software tools and raters. In some cases, this led to HERS Index Scores that were lower than they should have been. RESNET addressed the issue of unrealistic data entry in the HERS software programs by creating a set of internal bounds checks that must be incorporated by all RESNET accredited software tools by August 1, 2015. These checks will result in rejecting unrealistic data entries and flagging questionable entries for review by the Quality Assurance Designee and RESNET staff.”

    Because of the adoption of the ANSI-RESNET Standard 301-2014 and new RESNET quality assurance procedures, there will be changes in HERS Index Scores beginning October 1, 2015. To determine the potential effects of these changes, RESNET commissioned IBS Advisors to analyze what they might be.

    “The study reports that the implementation of ANSI/RESNET Standard 301-2014 this year will cause HERS Index scores to increase by an estimated 2 to 3 points due to infiltration and ventilation changes, and to decrease by an estimated 3 to 6 points due to changes related to efficient domestic water heating. This will result in a net benefit to energy efficient builders of 1 to 3 points in HERS Index Scores over the current calculations.

    The study reports that HERS Index scores for builders whose raters made data entries that were questionable may go up an average of 7 points once the new RESNET quality assurance policies are implemented and the software bounds checks are in place. This issue is HERS Rater specific. The report provides its analysis in aggregate and does not report on specific builders or HERS Raters.  The report can be downloaded at Upcoming Changes to the HERS Index and Potential Impact on HERS Index Scores.”

    The revised HERS software programs will be available after August 1, 2015, and HERS raters are encouraged to work with builders to determine how the changes will affect their scores. To allow builders an opportunity to adjust to these changes, RESNET has moved the date to when revised software programs must be used to October 1, 2015.


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