RESNET Adopts Innovative Design Request for the Determination of Drain Water Heat Recovery (DWHR) System HERS Index Credits

October 2nd, 2014 - Posted by RESNET under Hot Topics, RESNET News

Over 35,000 Drain Water Heat Recovery (DHWR) units have been installed in homes in North America. Thousands of units are also in operation in commercial buildings such as multi-family residential, hotels, recreation facilities and restaurants.  The “IECC 2015 – Commercial” specifically provides for energy credit tradeoffs and IECC 2015 has performance requirements (e.g. maximum pressure loss) for vertically installed DWHR units. The Ontario Building Energy Code also provides for energy credit tradeoffs for DWHR and Natural Resources Canada has had credits for DWHR for more than 7 years.

Fostering innovation that reduces residential energy consumption is a key role that RESNET plays. Water heating is a large energy load in homes and its contribution to total home energy load has increased in recent years as building envelops and mechanical systems improvements have resulted in significantly reduced energy consumption. However, DWHR systems have yet to be included in HERS.

RESNET has adopted an Innovative Design Request to calculate energy savings for DWHR systems and provide an appropriate HERS Index score credit where these systems are properly installed in homes.


The adopted Innovative Design Request addresses:

  • DWHR System Minimum Requirements
  • DWHR HERS Index Score Credit Calculation Procedure

To view the newly adopted procedures go to RESNET Drain Water Heat Recovery System HERS Index Credits

The web page includes instructions for completing DWHR HERS Index credit calculations.

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