BPI Diagnostic Testing & Performance Evaluation 2 — Questions and Answers
Question 1: During a blower door test, what does the metric 'CFM50' specifically measure?
- Airflow in cubic feet per minute at 50 Pascals of pressure difference (Correct answer)
- Carbon monoxide in cubic feet per minute at 50% humidity
- Combustion airflow at 50 degrees Fahrenheit
- Duct leakage at 50% of rated fan capacity
Correct answer: Airflow in cubic feet per minute at 50 Pascals of pressure difference
CFM50 is the volumetric airflow rate (in cubic feet per minute) required to maintain a 50 Pascal pressure difference across the building envelope.
Question 2: Which diagnostic tool is primarily used to detect moisture intrusion and thermal anomalies in building assemblies?
- Manometer
- Combustion analyzer
- Infrared camera (Correct answer)
- Anemometer
Correct answer: Infrared camera
Infrared (IR) cameras detect surface temperature differences that indicate moisture intrusion, missing insulation, or air leakage paths in building assemblies.
Question 3: What is the purpose of the 'house pressure' test conducted during combustion safety testing?
- To measure attic ventilation rates
- To determine if appliances can backdraft under worst-case depressurization (Correct answer)
- To calculate the building's infiltration rate
- To verify duct system balance
Correct answer: To determine if appliances can backdraft under worst-case depressurization
The worst-case house pressure test simulates maximum depressurization conditions to determine if combustion appliances are at risk of backdrafting.
Question 4: When performing duct leakage testing, a 'Duct Blaster' pressurizes the duct system to what standard test pressure?
- 25 Pascals (Correct answer)
- 50 Pascals
- 75 Pascals
- 100 Pascals
Correct answer: 25 Pascals
Duct leakage testing is standardized at 25 Pascals of pressure difference across the duct system walls.
Question 5: What does a negative pressure reading inside a mechanical room indicate during worst-case combustion safety testing?
- The room is well-ventilated and safe
- The room is depressurized, increasing backdraft risk for combustion appliances (Correct answer)
- The HVAC system is operating at peak efficiency
- Duct leakage is within acceptable limits
Correct answer: The room is depressurized, increasing backdraft risk for combustion appliances
A negative pressure in the mechanical room means it is depressurized relative to outdoors, which can draw combustion gases back into the living space.
Question 6: Which calculation uses blower door results to estimate the natural air changes per hour (ACH) of a building under normal conditions?
- The Lawrence Berkeley National Laboratory (LBL) infiltration model (Correct answer)
- The ASHRAE 62.2 ventilation rate procedure
- The Manual J load calculation
- The HERS rating index formula
Correct answer: The Lawrence Berkeley National Laboratory (LBL) infiltration model
The LBL infiltration model converts CFM50 data into estimated natural infiltration rates by applying climate and building-specific correction factors.
Question 7: During a blower door test, what condition must be achieved before taking pressure measurements?
- All interior doors must be open and all exterior openings sealed (Correct answer)
- The HVAC system must be running at full capacity
- All windows must be opened to equalize pressure
- The thermostat must be set below the outdoor temperature
Correct answer: All interior doors must be open and all exterior openings sealed
For an accurate blower door test, interior doors should be open to allow pressure to equalize throughout the house, while all intentional exterior openings are sealed.
BPI Diagnostic Testing & Performance Evaluation 2
During a blower door test, what does the metric 'CFM50' specifically measure?