Diagnostics & Performance Testing Flashcards

A HERS rater is testing a new construction home with a solar PV system. How does the PV system affect the HERS Index?

Answer: It lowers the HERS Index by offsetting calculated energy consumption

On-site PV generation reduces the home's net energy consumption in the HERS calculation, directly lowering the HERS Index score.

Which test condition must be established BEFORE beginning a duct blaster pressurization test?

Answer: All supply and return registers must be sealed and the air handler must be OFF

Registers are sealed so only duct system leakage is measured, and the air handler is off so it does not add airflow that would corrupt the duct blaster reading.

A rater uses an infrared camera during a blower door test and sees a bright cool pattern around a recessed light in a conditioned attic. What does this most likely indicate?

Answer: Air is infiltrating through the fixture from the unconditioned space above

Cool patterns on the IR camera during blower-door depressurization indicate cold outside air entering through gaps around the fixture, revealing an air leakage site.

What is the purpose of measuring 'room-to-room pressure differentials' during a HERS diagnostic inspection?

Answer: To identify rooms with poor return air pathways that can cause pressure imbalances

High room-to-room pressure differences (typically >3 Pa with the air handler running) indicate inadequate return air transfer, which can worsen duct leakage effects and IAQ.

Under ASHRAE 62.2-2016 referenced by HERS, what is the minimum whole-building ventilation rate formula for a 2,000 sq ft home with 3 bedrooms?

Answer: 0.03 CFM/sq ft + 7.5 CFM × (bedrooms + 1)

ASHRAE 62.2-2016 uses: Qtotal = 0.03 × floor area + 7.5 × (bedrooms + 1), giving 0.03 × 2000 + 7.5 × 4 = 60 + 30 = 90 CFM for this example.

A rater finds that a spray-foam insulated cathedral ceiling has no ventilation channel between the foam and the roof deck. How should this be handled in the HERS rating?

Answer: Verify the foam type and thickness; unvented assemblies are acceptable if designed per code with adequate R-value

Unvented cathedral ceiling assemblies are code-compliant when properly designed with sufficient closed-cell or open-cell foam meeting IRC Section R806.5 requirements; the rater verifies the design, not the ventilation gap.

During a duct system commissioning test, the technician measures 350 CFM at the air handler but only 310 CFM total at all supply registers. What does the 40 CFM discrepancy most likely represent?

Answer: Supply duct leakage into unconditioned spaces between the air handler and the registers

When total supply register airflow is less than measured air handler output, the difference represents air leaking out of supply ducts before reaching the registers.