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RESNET Board Establishes HERS® Software Consistency Collaborative Modeling Process

Apr 24, 2018
RESNET Board Takes Action to Enhance the Consistency of How Accredited HERS® Software Programs Calculate HERS® Index Scores
HERS® Software Consistency Collaborative Modeling Process Established
A key to ensuring the quality of HERS® ratings is to enhance the consistency which the various accredited HERS® software programs calculate HERS® Index Scores. Too often in the past, the same home could receive a different score based upon the software program being used.
For the past four years, the RESNET Board has strived to enhance the consistency of the calculation of HERS® Index Scores.
On April 19, 2018, the RESNET Board took another giant step forward with the adoption of a HERS® Software Consistency Collaborative Modeling Process. The process will create a mechanism by which RESNET can improve consistency of HERS® Index Scores and modeled energy consumption between RESNET accredited software tools and enhance accreditation testing parameters. This is intended to be a continuous, ongoing process to improve consistency.
The key feature of the process is the formation of a formal RESNET Board standing committee, the Software Consistency Committee (SCC). The SCC will have one primary purpose – to hear, evaluate, and respond to software modeling consistency inquires put forth by RESNET members. However, the SCC will also have the ability to proactively promote consistently through group discussion, updates to the RESNET Modeling Guidelines, recommended updates to Publication 002 test boundaries, and requests for Standards interpretations.
To support the SCC, RESNET will recruit a technical consultant with extensive knowledge of building energy software modeling, who will serve as the RESNET Energy Modeling Director.
RESNET staff will now begin the process of launching the HERS® Software Consistency Collaborative Modeling Process. Steps that will be taken include:
  • RESNET Board adoption of a charter for the Software Consistency Committee
  • Recruitment and appointment of the members of the SCC by the RESNET Board
  • Recruitment and appointment of a RESNET Energy Modeling Director by the RESNET Board
It is important to remember the steps that RESNET has taken to date to enhance the consistency of the calculation of HERS® Index Scores. Actions taken include:
  • Adoption of the RESNET Publication No. 002, “Procedures for Verification of RESNET Accredited HERS® Software Tools”. The publication sets a suite of tests that HERS® software programs must pass in order to be accredited by RESNET. The suite of tests are:
    • The HERS® Method Tests verify whether the software tools can accurately calculate the HERS® Index Score.
    • ANSI/ASHRAE Standard 140-2011, Class II, Tier 1 Test tests the accuracy of the software to model the base loads of a home.
      • HERS® Reference Home Auto-Generation Tests – verify the ability of the software tool to automatically generate the HERS® Reference Home.


    • HVAC Tests – verify the accuracy and consistency with which software tools predict the performance of HVAC equipment, including furnaces, air conditioners, and air source heat pumps.
    • Duct Distribution System Efficiency Tests verify the accuracy with which software tools calculate air distribution system losses. ASHRAE Standard 152 results are used as the basis for the test suite acceptance criteria.
    • Hot Water System Performance Tests – determine the ability of the software to accurately predict hot water system energy use.
  • Established limits on input variables for whole-house ventilation systems
  • Incorporated bounds checks into software to limit or warn HERS® raters when input values are beyond reasonable limits
  • Established QAD flags for internal inconsistencies that should be checked prior to entering a building file into RESNET registry
  • Development of a RESNET building input common schema. A common schema would be a file format with a standardized set of building input fields that facilitates the exchange of data/information between the accredited HERS® software tools.