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ANSI Adopts RESNET Domestic Hot Water Systems Amendment to the ANSI/RESNET Standard 301-2014

Feb 13, 2015

Currently hot water use and its attendant energy consumption are poorly represented by the procedures and calculations that are used for codes and standards and energy performance models. Much better data is now available from which hot water use and hot water energy consumption calculations may be computed. RESNET has been criticized by energy partner programs because its standards do not consider hot water distribution systems and advanced hot water technologies. Further, builder partners have expressed interest in additional opportunities to reduce energy use through smarter design and enhanced product choices.

To address these issues the RESNET Standards Management Board adopted and recommended to the American National Standard Institute (ANSI) an amendment to ANSI – RESNET 301 2014’s treatment of water heating, distribution and use. The amendment made the following improvements:

  • Revised the median set point temperature
  • Revised the calculation of hot water use by number of bedrooms
  • Revised the calculation of average total household hot water waste
  • Modified the calculation of hot water energy use in the Rated home
  • Incorporated the Drain Water Heat Recovery (DWHR) Systems

The proposed amendment went through the RESNET ANSI standard amendment public consensus review and comment process. ANSI has adopted the amendment.

RESNET Executive Director Steve Baden commented, “This is a major contribution to the accuracy of RESNET’s HERS® Index.  Hot water represents a major portion of a consumer’s energy bill.  This amendment will allow builders of energy efficiency homes to receive more credit for installing high performance water systems.  By being able to accurately rate the efficiency of a home’s water heating it lays a foundation for the development of a water efficient rating system.”