BPI Diagnostic Testing & Performance Evaluation 3 — Questions and Answers
Question 1: What is 'depressurization' in the context of BPI combustion safety testing?
- Lowering indoor humidity below outdoor levels
- Creating a negative pressure inside relative to outdoors (Correct answer)
- Reducing static pressure in duct systems
- Decreasing combustion appliance firing rate
Correct answer: Creating a negative pressure inside relative to outdoors
Depressurization occurs when the indoor pressure is lower than outdoor pressure, which can cause combustion appliance flue gases to flow backward into living spaces.
Question 2: A home tests at 2,400 CFM50 and has a volume of 12,000 cubic feet. What is the ACH50 value?
- 5
- 10
- 12 (Correct answer)
- 20
Correct answer: 12
ACH50 = (CFM50 × 60 minutes) ÷ building volume = (2,400 × 60) ÷ 12,000 = 12 ACH50.
Question 3: Which of the following best describes 'thermal bypass' as identified during an infrared scan?
- Heat transfer through a window frame via conduction
- Airflow that carries heat around or through insulation, reducing its effectiveness (Correct answer)
- Radiant heat gain through south-facing glazing
- Conductive heat loss through an uninsulated slab edge
Correct answer: Airflow that carries heat around or through insulation, reducing its effectiveness
Thermal bypass occurs when air movement through gaps in the building assembly carries heat around insulation, dramatically reducing its thermal resistance.
Question 4: In BPI standards, what is the maximum acceptable CO level in ambient air inside a home during combustion appliance testing?
- 9 ppm (Correct answer)
- 35 ppm
- 70 ppm
- 200 ppm
Correct answer: 9 ppm
BPI standards require that ambient CO levels not exceed 9 ppm (the EPA's 8-hour outdoor standard) before proceeding with energy upgrades.
Question 5: What diagnostic condition is indicated when a blower door test shows much lower CFM50 than expected for a building's age and size?
- The building has excessive duct leakage
- Previous air sealing work may have been completed, or the building has unusual construction (Correct answer)
- The blower door fan is malfunctioning at low speeds
- The building has significant stack effect problems
Correct answer: Previous air sealing work may have been completed, or the building has unusual construction
Unusually low CFM50 results may indicate prior weatherization work, unusually tight construction methods, or possibly test setup errors that should be verified.
Question 6: What does measuring 'static pressure' across an air handler reveal about HVAC system performance?
- The refrigerant charge level in the system
- How much resistance the air distribution system presents to the fan (Correct answer)
- The outdoor temperature differential across the heat exchanger
- The duct leakage rate to the outside
Correct answer: How much resistance the air distribution system presents to the fan
Static pressure measurements across the air handler indicate total external static pressure, revealing whether the duct system resistance is within the equipment's design parameters.
Question 7: During infrared thermography, which condition produces the best contrast for detecting air leakage through the building envelope?
- Minimal temperature difference between indoors and outdoors
- At least a 10°F (18°C) temperature difference between indoors and outdoors (Correct answer)
- Outdoor temperatures above 90°F with AC running
- Midday sunshine with clear skies
Correct answer: At least a 10°F (18°C) temperature difference between indoors and outdoors
Infrared thermography requires a sufficient temperature differential (typically 10°F minimum) to create detectable surface temperature anomalies at air leakage sites.
BPI Diagnostic Testing & Performance Evaluation 3
What is 'depressurization' in the context of BPI combustion safety testing?