HERS Cheat Sheet 2026

The 30 highest-yield HERS facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Which insulation material has the highest R-value per inch, making it useful where space is limited in a HERS-rated home? → Closed-cell spray polyurethane foam
2. What AFUE rating is the minimum threshold for a gas furnace to be considered high-efficiency under current U.S. energy standards? → 90%
3. Which RESNET/ANSI standard governs water heating energy calculations in HERS ratings? → ANSI/RESNET/ICC 301-2014 (and subsequent amendments)
4. In HERS rating calculations, on what is the daily domestic hot water consumption estimate primarily based? → Number of bedrooms in the home
5. How does shading impact energy modeling? → Reduces cooling demand
6. For HERS purposes, what does the 'hot water distribution system efficiency' credit account for? → Energy losses from pipe heat dissipation and water wasted waiting for hot water to arrive
7. Which of the following conditions is most likely to cause backdrafting of a natural draft water heater? → Operation of a powerful, uncompensated kitchen exhaust fan.
8. What is the primary purpose of building science in residential construction? → Analyze energy, moisture, and air flow
9. A HERS rater is verifying a geothermal heat pump installation. Which performance metric is most relevant for its heating mode efficiency? → COP
10. In HERS energy modeling, how is incoming cold water (mains) temperature typically determined? → Location-dependent values based on ground temperature data
11. What role does ventilation play in building science? → Controls indoor air quality
12. Under IECC 2021 for climate zone 5, what is the minimum required attic insulation R-value for a new home? → R-49
13. What is the purpose of energy modeling in home performance analysis? → Optimize design for energy efficiency
14. Which component of the building envelope does the HERS rating system assess using a U-factor rather than an R-value? → Fenestration (windows and doors)
15. Which ventilation strategy meets ASHRAE 62.2 requirements by continuously exhausting stale air from bathrooms or kitchens at a calculated whole-house rate? → Exhaust-only ventilation
16. According to RESNET/ANSI 301, the HERS reference design water heater efficiency is based on what? → Federal minimum efficiency standards for the installed fuel type
17. What is the HERS Index Score? → A numerical energy performance rating
18. In HERS energy modeling, what is the thermal performance metric used to describe the insulating value of a wall assembly including all components? → Assembly R-value (whole-wall R-value)
19. During a HERS inspection, a rater verifies that a new home uses an HRV. What is the primary energy benefit of an HRV over exhaust-only ventilation? → It recovers heat from exhaust air to pre-condition incoming fresh air
20. What factor most affects heating and cooling load in a home? → Insulation and orientation
21. What does RESNET stand for in the HERS rating system? → Residential Energy Services Network
22. What does a high static pressure reading in a forced-air HVAC system indicate to a HERS rater? → There is likely restricted airflow due to undersized ducts or a dirty filter
23. Which software tool is commonly used for HERS energy modeling? → REM/Rate
24. In REM/Rate energy modeling, how is a heat pump water heater typically entered to reflect its efficiency correctly? → Using the Uniform Energy Factor (UEF) from the EnergyGuide label
25. What credit does a solar water heating system receive in a HERS rating? → Credit based on the calculated solar fraction and system efficiency per RESNET standards
26. A HERS Rater is explaining the HERS Index to a client. What does a HERS Index score of 100 signify? → The home's energy performance is equivalent to that of the HERS Reference Home.
27. Which metric is used to rate the cooling efficiency of central air conditioning systems on the HERS rating? → SEER
28. What is the benefit of using dense-pack cellulose in existing wall cavities during an energy retrofit verified by a HERS rater? → It fills voids and gaps that batts cannot reach, improving both insulation and air sealing
29. A HERS rater finds duct leakage to outside of 8% of system airflow. Under RESNET standards, how is this reported? → Pass — within the 10% default allowance
30. Which hot water distribution system configuration typically results in the best delivery efficiency in a HERS rating? → Compact distribution system with short runs and small-diameter pipes