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HERS Raters Can Credit Drain Water Heat Recovery Systems Lower HERS Scores

Jul 26, 2023

The ANSI/RESNET/International Code Council Standard 301 incorporates new water heating efficiency calculations, including Drain Water Heat Recovery (DWHR) in calculating a home’s HERS® Index Score.  RESNET accredited HERS® Rating Software programs were to incorporate the new standard in their software tools beginning on January 1, 2016.  As a result of inconsistencies in incorporating the new standard, the RESNET Board of Directors moved the date that HERS® Raters must use the revised software programs to July 1, 2016.

Despite this delay, HERS® Raters can still credit DWHR systems through the Innovative Design Request that RESNET has adopted to calculate energy savings for DWHR systems and provide an appropriate HERS® Index score credit where these systems are properly installed in homes.

The RESNET Drain Water Heat Recovery Innovative Design Request will remain in effect until the revised HERS® rating software tools go into effect.

For information on how to incorporate DWHR systems into a HERS® rating along with an example of completed determination of DWHR Systems for HERS® Index credits go to RESNET Innovative Design Request on Drain Water Recovery