HERS Diagnostic and Field Testing Questions and Answers 1 — Questions and Answers
Question 1: A HERS Rater performs a blower door test on a new construction home and obtains a result of 6.5 ACH50. The applicable energy code for the jurisdiction requires a maximum of 5.0 ACH50. While the blower door is still running, which of the following is the most effective and direct method for the rater to identify the largest air leakage pathways?
- Using an infrared camera to scan the interior surfaces of the thermal envelope.
- Conducting zonal pressure diagnostics by measuring pressure differences between rooms.
- Systematically feeling for drafts by hand at common leakage points like sill plates and window frames. (Correct answer)
- Releasing theatrical smoke outside the building and observing where it is drawn in.
Correct answer: Systematically feeling for drafts by hand at common leakage points like sill plates and window frames.
While an infrared camera and zonal pressure diagnostics are valuable tools, the most direct and often most effective initial step is to use your senses. With the house depressurized to -50 Pascals, significant leaks are often obvious and can be felt by hand or seen with a smoke puffer at common problem areas such as sill plates, band joists, window/door trim, and penetrations for wiring and plumbing. This allows for quick identification and subsequent sealing.
Question 2: During a duct leakage test on a system located entirely within the conditioned space, a rater can perform either a 'total duct leakage' test or a 'leakage to outside' test. According to RESNET standards, which test result can be used for compliance if the goal is to meet a 'leakage to outside' requirement?
- Only the 'leakage to outside' test result is acceptable.
- Neither test is appropriate; a visual inspection is required instead.
- The 'total duct leakage' test result can be used, as it will always be greater than or equal to the leakage to the outside. (Correct answer)
- The two test results must be averaged to determine compliance.
Correct answer: The 'total duct leakage' test result can be used, as it will always be greater than or equal to the leakage to the outside.
According to RESNET Standard ANSI/RESNET/ICC 380, the total duct leakage test measures all leaks in the system, both to the inside and outside of the conditioned space. The 'leakage to outside' test is more complex, requiring a blower door to pressurize the house simultaneously. Because total duct leakage will always be a higher (or equal) value than leakage to the outside, its result can be conservatively used to demonstrate compliance with a leakage-to-outside standard.
Question 3: A rater is preparing to conduct a worst-case depressurization test in a Combustion Appliance Zone (CAZ) containing a natural draft water heater and a furnace. Which of the following is a critical first step in the standard procedure?
- Immediately fire the largest combustion appliance to warm the flue.
- Turn on all exhaust fans and the furnace air handler simultaneously.
- Establish and record the baseline pressure of the CAZ with reference to the outdoors before turning on any fans or appliances. (Correct answer)
- Pressurize the house to +50 Pa with a blower door to identify any pre-existing backdrafting.
Correct answer: Establish and record the baseline pressure of the CAZ with reference to the outdoors before turning on any fans or appliances.
Before inducing depressurization by turning on exhaust fans and air handlers, it is essential to measure the baseline pressure difference between the CAZ and the outdoors. This baseline reading is the starting point from which the 'worst-case' depressurization level is calculated after all air-moving equipment is activated. Without this baseline, the net effect of the exhaust appliances cannot be accurately determined.
Question 4: A HERS Rater is using an infrared camera to inspect a wall cavity on a cold day. The camera shows a distinct, cool, feathery pattern on the interior drywall surface. This pattern most likely indicates:
- A void or gap in the insulation allowing for air leakage and convection. (Correct answer)
- The normal location of wood framing members conducting heat to the outside.
- Surface moisture or condensation due to a high interior relative humidity.
- A thermal bridge caused by a steel structural component.
Correct answer: A void or gap in the insulation allowing for air leakage and convection.
Cool, irregular, or feathery patterns seen with an infrared camera on a building surface typically indicate air leakage. The moving air cools the surface in a distinct pattern as it passes through gaps in the insulation or air barrier. In contrast, framing members (thermal bridges) usually appear as uniform, cooler vertical or horizontal lines, and moisture often has a more amorphous, splotchy appearance.
Question 5: When performing a zonal pressure diagnostic test with a blower door running, a rater measures the pressure difference between an attached garage and the main house. The reading is -45 Pa (Pascals). What does this reading indicate?
- The HVAC system is severely unbalanced between the house and the garage.
- The garage is well-sealed from the outdoors but has a very leaky connection to the house.
- A large amount of duct leakage is occurring within the garage.
- The air barrier between the house and the garage is very effective (tight). (Correct answer)
Correct answer: The air barrier between the house and the garage is very effective (tight).
During a blower door test where the house is depressurized to -50 Pa relative to the outdoors, any zone that is well-connected to the outdoors and well-sealed from the house will approach -50 Pa. A reading of -45 Pa indicates a very small pressure difference between the garage and the outdoors, meaning the primary air barrier between the house and the garage is intact and performing well. A low reading (e.g., -5 Pa) would indicate a leaky barrier.
Question 6: Which of the following conditions must be met for a rater to safely proceed with measuring the Carbon Monoxide (CO) levels in the flue gas of a combustion appliance during a CAZ test?
- The flame must be blue with consistent orange tips.
- The ambient CO level in the CAZ must remain below 35 ppm. (Correct answer)
- The appliance must demonstrate spillage for at least 60 seconds to ensure a proper sample can be taken.
- The flue draft pressure must be positive, indicating strong updraft.
Correct answer: The ambient CO level in the CAZ must remain below 35 ppm.
Safety is the primary concern during combustion testing. Standards require that if the ambient carbon monoxide level in the CAZ rises to 35 parts per million (ppm) or higher at any point, the test must be stopped immediately. The area must be ventilated, and the cause of the high CO must be identified and corrected before testing can resume. Proceeding with testing above this threshold poses a serious health risk to the rater and occupants.
HERS Diagnostic and Field Testing Questions and Answers 1
A HERS Rater performs a blower door test on a new construction home and obtains a result of 6.5 ACH50.
The applicable energy code for the jurisdiction requires a maximum of 5.0 ACH50.
While the blower door is still running, which of the following is the most effective and direct method for the rater to identify the largest air leakage pathways?