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. In building science, what does 'hygrothermal analysis' evaluate? → The combined heat and moisture movement through building assemblies over time
2. Which standard of practice is MOST important for ensuring quality in HERS Index Scoring? → Following evidence-based protocols while adapting to specific circumstances
3. What is the primary advantage of a demand (tankless) water heater over a storage water heater? → It eliminates standby heat losses because it heats water only when needed
4. Under RESNET standards, which of the following is required before a trainee rater can file ratings independently? → Completing a minimum of field mentored ratings and passing required exams
5. A home has a Duct Leakage to Outside of 8% of floor area. Under ENERGY STAR v3.2, what is the maximum allowable Qto as a percentage of conditioned floor area? → 4%
6. Why is mastic sealant generally preferred over standard duct tape for sealing duct leaks? → Mastic remains flexible and durable, while duct tape adhesive degrades over time
7. What does the term 'tilt angle' refer to in a solar PV installation? → The angle between the panel surface and horizontal ground
8. In which climate condition is an Energy Recovery Ventilator (ERV) generally preferred over a Heat Recovery Ventilator (HRV)? → Hot-humid climates (IECC zones 1-3) where moisture control is critical
9. A negative HERS Index score (e.g., HERS −10) means the home: → Produces more energy than it consumes on an annual basis
10. For HERS credit purposes, what information is required to model a solar water heating system? → Collector area, collector orientation/tilt, and solar fraction or system details
11. Which of the following is an example of radiant heat transfer? → Sunlight warming a room through a window
12. What is the standard test pressure used for blower door testing when collecting data for HERS ratings? → 50 Pascals
13. In a two-story home with an attached conditioned garage, which assembly is part of the thermal envelope? → The wall and ceiling between the conditioned living space and the garage
14. Which metric is used by the HERS Index to compare the rated home's water heating energy use against the reference home? → Annual water heating energy consumption in kBtu/yr calculated by the rating software
15. In Energy Modeling Software, what is the FIRST step a HERS professional should take when encountering a new case or situation? → Conduct a comprehensive assessment and gather all relevant information
16. Why is it important to conduct combustion safety testing? → To verify safe venting of combustion gases
17. Which standard provides the test method for measuring air leakage of building envelopes using a blower door? → ASTM E779
18. A supply-only ventilation system in a hot-humid climate can create which building science concern? → Pressurization that drives warm humid air into wall cavities, risking moisture damage
19. Which renewable energy system type generates electricity from heat produced by a temperature differential between a fluid and its surroundings? → Thermoelectric generators
20. The 'stack effect' contributes to air infiltration in buildings. Which condition MAXIMIZES stack effect-driven infiltration? → Cold winter days with a tall building and large vertical temperature difference
21. What is the primary purpose of the HERS reference home in the rating system? → To provide a standardized baseline for comparing energy performance
22. Under the RESNET Mortgage Industry National Home Energy Rating Standards, which document must a rater provide to a homeowner upon completion of a rating? → The HERS Index report
23. Which ventilation standard is referenced in RESNET guidelines to determine whole-house mechanical ventilation requirements for HERS ratings? → ASHRAE 62.2
24. Which RESNET standard governs HERS field verification sampling protocols? → ANSI/RESNET/ICC 380
25. What ethical obligation does a HERS rater have if they lack the technical competency required for a specialized rating task (e.g., multifamily high-rise)? → Decline the work or obtain additional training before proceeding
26. A home has a measured air leakage of 1,800 CFM50 and a conditioned volume of 15,000 cubic feet. What is the ACH50? → 7.2
27. A rater finds that duct leakage to the outside is 8% of system airflow. How does this compare to the ENERGY STAR v3.1 threshold? → It fails; ENERGY STAR requires 4% or less
28. Which mechanism is responsible for the majority of heat transfer through a well-sealed, well-insulated attic floor on a cold winter night? → Conduction through the insulation material
29. A rim joist is a common air leakage site in older homes. Which insulation method best addresses both air sealing and thermal performance at the rim joist? → Spray foam applied directly to the rim joist
30. Which RESNET standard governs the accreditation of HERS rating software tools? → RESNET/ICC Standard 301