Duct Leakage Testing Flashcards
7 cards from real HERS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Duct Leakage Testing flashcards as text
What effect does supply duct leakage in an attic have on a home's cooling load in a hot climate?
Answer: It increases cooling load because cool conditioned air is lost to unconditioned attic space
Supply duct leakage in a hot attic loses cool conditioned air to unconditioned space, forcing the system to run longer and increasing cooling loads significantly.
How is the 'effective leakage area' (ELA) of a duct system different from CFM25?
Answer: ELA expresses leakage as an equivalent hole area rather than airflow rate
Effective leakage area (ELA) converts duct leakage into an equivalent square-inch hole size, providing an intuitive geometric representation of the total leakage pathway.
A rater tests duct leakage in a home with a partially unconditioned basement. Some ducts run through both conditioned and unconditioned zones. How should Qto be characterized?
Answer: Only leakage from ducts in the unconditioned basement counts toward Qto
Only leakage occurring through duct portions that communicate with unconditioned space (the unconditioned basement) contributes to Qto; leakage within the conditioned zone does not.
Which of the following is NOT a valid method to verify that all registers are properly sealed before a duct leakage test?
Answer: Checking pressure at each register with a digital manometer
Checking pressure at each register with a manometer measures static pressure, not whether the register is physically sealed against airflow leakage during the test.
What is the significance of the 'can lights' above a dropped ceiling in relation to duct leakage testing?
Answer: Can lights can create pathways between conditioned and unconditioned space that confound Qto measurement
Recessed can lights above dropped ceilings can create air pathways between conditioned and unconditioned space, potentially affecting pressure measurements during Qto testing.
A rater finds that sealing all visible duct leaks still leaves total leakage above the code threshold. What advanced diagnostic technique can pinpoint remaining hidden leaks?
Answer: Infrared thermography with the HVAC system operating
Infrared thermography with the system running reveals temperature differentials at hidden leakage sites such as behind walls or above ceilings, helping locate leaks not visible to the eye.
Under IECC 2021, what is the maximum permitted total duct leakage for new residential construction when tested at rough-in?
Answer: 4 CFM25 per 100 sq ft
IECC 2021 requires total duct leakage at rough-in (with air handler not yet installed) to not exceed 4 CFM25 per 100 sq ft of conditioned floor area.