The Home Energy Rating System (HERS) Rating Process

Marc performing blower door testing for building air leakage

In addition to the HERS energy audit process information on this page, see specific information for HERS ratings and energy audits for new homes, existing homes, commercial ratings and Stretch Energy Code and the 2015 IECC code compliance, and an explanation of what a HERS rating is, and how it's scored.

What does a HERS energy rating include ?

An HERS energy rating includes following:

  • Projected rating based on plans and specifications for permit
  • Site visits to guide energy efficient building details and code compliance
  • Inspection of insulation installation
  • Testing of HVAC duct systems
  • Blower door test of overall building air leakage
  • Testing of bath fan ventilation
  • Documentation of mechanical system model numbers
  • Documentation of appliance model numbers
  • Survey of lighting
  • Input of all information into rating software
  • Code compliance certification
  • Mass Save rebate administration

What are the steps in the HERS rating process?

Here are the steps in the HERS rating process:

  1. Review building plans
  2. Review specifications for insulation and mechanical systems
  3. Complete a projected rating based on plans and specifications
  4. Modify insulation or mechanical specifications if needed to meet building code standard of HERS 55.
  5. Provide a projected HERS certificate to present to the Building Inspector for permitting.
  6. Submit application to Mass Save New Construction Program for incentive rebates (if eligible)
  7. Provide recommended framing details and air sealing checklist.
  8. Meet with Builder on site to review insulation strategy
  9. Inspect/photograph insulation upon completion
  10. Test duct systems for air leakage/code compliance
  11. Duct leakage certification for code compliance
  12. Collect documentation as required for HVAC efficiency
  13. Provide Builder with catalogue of available Free LED light bulbs from Mass Save (if eligible)
  14. Order Free LED bulbs from Mass Save (if eligible)
  15. Final testing and documentation
    • a) Document meter numbers
    • b) Document HVAC equipment model numbers and efficiency
    • c) Document hot water heating equipment model numbers and efficiency
    • d) Document appliance model numbers and efficiency
    • e) Survey/document lighting efficiency
  16. Blower door test/code compliance
  17. Ventilation testing of bath fans
  18. Input all efficiency information and test results into software for HERS rating
  19. Final HERS rating and documentation
    • a) HERS certificate
    • b) HERS sticker for electric panel
    • c) 2015 IECC certificate
    • d) 2015 IECC sticker for electric panel
    • e) Air leakage certificate
  20. Submit final HERS rating to Mass Save for incentive rebate

How does a blower door test work, and what is passing?

Blower door testing is a way to test the air leakage of a house’s building envelope. The idea is that a building with a tighter envelope is going to require less heating and cooling. Using a blower door the building is depressurized to a code standard (-50 Pascals). At this level of depressurization the HERS rater measures the leakage rate (cubic feet per minute). The HERS rater then compares the leakage rate with the total volume of air within the space that is within the insulation envelope. The code standard is that within an hour, under the depressurization of the blower door, the total volume of air would change no more than 3 times. This is referred to as 3 ACH/50. To pass the test the ACH/50 has to be 3 or less. For more information on blower door testing watch this Youtube video:


What do I need to keep the house environment healthy if the house is so tight?

In combination with a tight building shell the code requires a ventilation system to maintain healthy indoor air during the portion of the year when windows are not being left open. In houses with central AC systems, that could be all year. To meet the code ventilation requirement a house must be equipped with either a continuous exhaust only system (bath fan) which will depressurize the house and force outdoor air in through whatever paths exist (small holes), or an Energy Recovery Ventilation system (ERV) which provides a continuous supply of fresh air which is preheated by the heat of air which is being exhausted. Factors which influence the code standard for ventilation are the overall floor area of the house, as well as the number of bedrooms. In general, smaller houses (less than 2500 square feet) can meet the ventilation requirement with a continuously operating bath fan. Houses over 3000 square feet will be better served by an ERV in meeting the ventilation requirement. An ERV system has the added benefit of maintain the house in neutral pressure. All ventilation systems act to reduce indoor humidity levels which is healthier for occupants and better for building durability.

For more information read this article from the Building Performance Institute - Technically Speaking: Whole-House Mechanical Ventilation