BAP BAP Weatherization & Retrofit Measures 2 — Questions and Answers
Question 1: What does 'ACH50' measure in the context of building performance testing?
- The average cubic feet per minute of duct leakage at 25 Pascals
- The number of times the building's air volume is exchanged per hour at 50 Pascals of pressure (Correct answer)
- The air changes per hour needed for ASHRAE 62.2 mechanical ventilation
- The conditioned floor area divided by the blower door CFM50 reading
Correct answer: The number of times the building's air volume is exchanged per hour at 50 Pascals of pressure
ACH50 (air changes per hour at 50 Pascals) normalizes blower door CFM50 by the building volume, allowing comparison of airtightness across differently sized homes.
Question 2: After tightening a home's envelope, what must a BAP analyst verify to maintain indoor air quality?
- That window U-values meet current Energy Star specifications
- That mechanical ventilation is adequate per ASHRAE 62.2 or equivalent standard (Correct answer)
- That all recessed lighting fixtures are ICAT-rated
- That the HVAC filter is replaced before leaving the job site
Correct answer: That mechanical ventilation is adequate per ASHRAE 62.2 or equivalent standard
Tightening the envelope reduces natural infiltration, so mechanical ventilation must be verified or added to maintain acceptable indoor air quality per ASHRAE 62.2.
Question 3: What is the purpose of a 'house-to-outside' duct leakage test (Qn,out)?
- To measure total duct leakage including leakage between ducts and conditioned space
- To quantify only the duct leakage that goes to unconditioned spaces outside the thermal envelope (Correct answer)
- To determine the supply-to-return pressure imbalance in a zoned HVAC system
- To identify which specific duct sections are leaking by room pressure mapping
Correct answer: To quantify only the duct leakage that goes to unconditioned spaces outside the thermal envelope
Duct leakage to outside (Qn,out) measures only the leakage from ducts into unconditioned spaces like attics or crawlspaces — the leakage that directly wastes conditioned air.
Question 4: In a hot-humid climate (US Climate Zone 2), where should the vapor retarder generally be located in a wall assembly?
- On the interior face of the stud cavity, behind the drywall
- On the exterior side of the sheathing, beneath the cladding
- Vapor retarders are not recommended in hot-humid climates (Correct answer)
- In the center of the cavity between two layers of insulation
Correct answer: Vapor retarders are not recommended in hot-humid climates
In hot-humid climates, interior vapor barriers trap moisture driven inward by cooling systems, so most building codes and energy programs avoid interior vapor retarders in these zones.
Question 5: What R-value per inch does open-cell spray polyurethane foam (ocSPF) typically provide?
- R-3.5 to R-3.8 per inch (Correct answer)
- R-6 to R-7 per inch
- R-1.5 to R-2 per inch
- R-10 to R-12 per inch
Correct answer: R-3.5 to R-3.8 per inch
Open-cell SPF provides approximately R-3.5 to R-3.8 per inch due to its lower density and partially open cell structure, compared to about R-6 per inch for closed-cell SPF.
Question 6: What is a key limitation of using a blower door to identify air leakage locations versus quantifying total air leakage?
- The blower door cannot reach 50 Pascals in homes with open floor plans
- Locating leaks requires additional diagnostic tools like smoke pencils or infrared cameras; the blower door only measures total leakage (Correct answer)
- Blower door results are only valid when outdoor temperature is below 40°F
- The blower door fan cannot be used simultaneously with a duct blaster
Correct answer: Locating leaks requires additional diagnostic tools like smoke pencils or infrared cameras; the blower door only measures total leakage
The blower door quantifies total envelope leakage (CFM50) but does not identify locations; smoke pencils, theatrical fog, or IR thermography are needed to pinpoint specific leaks.
BAP BAP Weatherization & Retrofit Measures 2
What does 'ACH50' measure in the context of building performance testing?