HERS Diagnostics & Performance Testing 2 — Questions and Answers
Question 1: During a duct leakage test, the technician measures a Qn (duct leakage to outside) of 0.12. What does this indicate?
- Duct system is within acceptable limits for most programs
- Duct leakage exceeds typical Energy Star thresholds (Correct answer)
- The blower door is malfunctioning
- The duct system is completely sealed
Correct answer: Duct leakage exceeds typical Energy Star thresholds
A Qn of 0.12 (12% of system airflow) is well above typical Energy Star thresholds of 0.06 or 6%, indicating excessive duct leakage.
Question 2: What instrument is used to measure airflow at individual supply and return registers during a HERS field verification?
- Manometer
- Flow hood (balometer) (Correct answer)
- Anemometer
- Pitot tube only
Correct answer: Flow hood (balometer)
A flow hood (balometer) is placed over a register to directly measure the airflow volume in CFM at each supply or return grille.
Question 3: A house tests at 4.2 ACH50 on the blower door. If the HERS Index target requires ≤3.0 ACH50, what is the next appropriate step?
- Accept the result since it is under 5.0
- Identify and air seal leakage sites, then retest (Correct answer)
- Switch to a larger blower door fan
- Report a passing result using the default assumption
Correct answer: Identify and air seal leakage sites, then retest
The rater must locate air leakage pathways using smoke sticks or infrared imaging, perform air sealing, and retest to confirm compliance.
Question 4: Which of the following best describes the purpose of a pressure pan test?
- Measures total system airflow at the air handler
- Identifies which duct branches are leaking by pressurizing individual registers (Correct answer)
- Determines the static pressure across the air filter
- Verifies the thermostat setpoint accuracy
Correct answer: Identifies which duct branches are leaking by pressurizing individual registers
A pressure pan (blocking pan) placed over a register and connected to a manometer identifies leaky duct sections by showing elevated pressure relative to the house.
Question 5: When testing for combustion safety, a technician measures a Carbon Monoxide (CO) concentration of 35 ppm in the appliance flue gas. What action is required?
- No action; 35 ppm is within safe limits
- Immediately shut down the appliance and notify the owner (Correct answer)
- Increase combustion air supply and retest
- Record the reading and continue the HERS inspection
Correct answer: Immediately shut down the appliance and notify the owner
A CO reading of 35 ppm in the flue is dangerously elevated; the appliance must be shut down and the owner notified before continuing the inspection.
Question 6: What does the term 'total duct leakage' (Qtotal) represent in duct blaster testing?
- Leakage only from supply ducts to the outside
- All air leaking from the duct system into both conditioned and unconditioned spaces (Correct answer)
- Leakage from the return system only
- The difference between supply and return airflow
Correct answer: All air leaking from the duct system into both conditioned and unconditioned spaces
Qtotal measures all air escaping the duct system regardless of destination — into conditioned space, unconditioned space, or outside.
Question 7: A HERS rater performing a mechanical ventilation verification discovers the measured exhaust flow is 45 CFM but the design calls for 60 CFM. What is the correct finding?
- Pass, because 45 CFM is within 25% of design
- Fail, because the measured flow does not meet the designed ventilation rate (Correct answer)
- Pass, because exhaust-only systems have a 20 CFM tolerance
- Fail only if the house is smaller than 2,000 square feet
Correct answer: Fail, because the measured flow does not meet the designed ventilation rate
HERS field verification requires that measured mechanical ventilation airflow meet or exceed the design rate; 45 CFM versus a 60 CFM design is a failing condition.
HERS Diagnostics & Performance Testing 2
During a duct leakage test, the technician measures a Qn (duct leakage to outside) of 0.12.
What does this indicate?