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RESNET Embarks on Enhancing the Consistency for Calculating HERS Index Scores Through a New RESNET Single-Source HERS Index Tool

Mar 8, 2016

As part of its commitment to excellence, RESNET has committed to a comprehensive effort to enhance the consistency of HERS Index scores.

This holistic commitment to quality includes:

Enhancing the Qualification of HERS Raters RESNET is concluding a consensus based effort to enhance its standard for the training, assessment and certification of HERS raters.

Enhancing RESNET Rating Quality Assurance ProceduresRESNET has embarked on a consensus based standard amendment process to enhance its HERS rating quality assurance standards.  This effort will include using automated quality assurance review by RESNET on all HERS rated homes.

Providing Adequate Resources for RESNET’s Quality Assurance InfrastructureIn its 2016 budget the RESNET Board of Directors authorized the financial resources to implement its enhancement of quality assurance activities.

Enhance the Consistency of Calculation of HERS Index Scores– A key pillar of RESNET’s commitment to quality is for RESNET accredited HERS software programs to consistently calculate the HERS Index.  RESNET has embarked on an effort to enhance this consistency.

The need for this action was best demonstrated by RESNET having to extend the implementation of the ANSI/RESNET/ICC Standard 301 to July 1, 2016.  This delay was caused by the inconsistency of the accredited HERS software programs in implementing the new standard.

To address this issue, RESNET has adopted an internal check system within RESNET accredited HERS software programs to reduce the inconsistency of inputs into the software programs.

In addition, the RESNET Board of Directors committed to developing a nationally consistent process for calculating the HERS Index.  The elements of this effort include:

  • A requirement that in the future all accredited HERS software programs must be based on hourly simulation modeling
  • Development of a RESNET Single-Source HERS Index Tool

RESNET Single-Source HERS Index Tool

Consistency in calculating the HERS Index is currently challenged by lack of a robust tool input quality assurance, differences in how the standards are interpreted and implemented, differences in how a limited number of inputs characterizing Minimum Rated Features are utilized to drive robust simulation engines and differences in simulation engines.

The objective of this project is to develop a single, centralized software resource for obtaining a RESNET HERS Index.  This capability will be available for use by RESNET accredited HERS software tools.  This resource will calculate and make available energy and HERS Index values; however, it will not provide user interfaces or formatted reports.  HERS software providers will be alleviated of developing and maintaining code implementing RESNET/ANSI/ICC Standard 301 as well as a building energy simulation engine. This will allow them to focus on business support and the user experience.  This new resource will leverage the publically available, and broadly supported, EnergyPlus Building Energy Simulation Software.

The goals for this effort are:

  • Improve consistency within HERS
  • Provide transparency
  • Increase the speed with which new, emerging efficiency technologies are recognized in HERS.

The RESNET Single-Source HERS Index Project will involve developing open-source software that provides a HERS Index and associated data per ANSI/RESNET/ICC Standard 301.  RESNET will be the steward of the software, host the program and manage it going forward.  This software shall take input from third party HERS software providers and return results; it will not include an input interface or formatted reports that compete with third-party software providers.  RESNET has contracted with Rob Salcido of Salcido Solutions to lead the project.

There will be an option for HERS Software Providers to develop their own tools.  To accommodate this, the project will include updating “Procedures for Verification of RESNET Accredited HERS Software Tools” (RESNET Publication No. 002-15) based on EnergyPlus, providing an accreditation pathway for HERS tools not utilizing the RESNET Single-Source HERS Index resource.

To guide the development of the RENET single-source tool RESNET has appointed a subject matter expert advisory committee.  The advisory committee is composed of:

  • Philip Fairey, Florida Solar Energy Center
  • Dean Gamble, Environmental Protection Agency ENERGY STAR
  • Cy Kilbourne, Ekotrope
  • Dave Roberts, National Renewable Energy Laboratory
  • Amber Wood, NORESCO
  • Bill Wright, Wrightsoft

The RESNET board tasked the subject matter expert advisory committee to develop and submit a detailed, technical plan for providing the single-source HERS Index solution to the board within 60 days.