BPI Diagnostic Testing & Performance Evaluation 4 — Questions and Answers
Question 1: What is the primary purpose of performing a 'duct leakage to outside' test rather than a 'total duct leakage' test?
- To determine leakage from supply ducts only, excluding return ducts
- To measure only the duct leakage that directly affects energy loss to unconditioned spaces (Correct answer)
- To calculate the maximum duct airflow capacity
- To identify which specific ducts require replacement
Correct answer: To measure only the duct leakage that directly affects energy loss to unconditioned spaces
Duct leakage to outside measures only leaks to unconditioned spaces (attic, crawlspace, garage), which directly impact energy efficiency, unlike interior leaks that recirculate conditioned air.
Question 2: Which BPI diagnostic protocol requires testing all exhaust fans operating simultaneously with the blower door?
- Standard blower door airtightness test
- Worst-case combustion safety depressurization test (Correct answer)
- Duct blaster pressurization test
- Room-to-room pressure balancing test
Correct answer: Worst-case combustion safety depressurization test
The worst-case combustion safety test activates all exhaust fans, the clothes dryer, and the blower door simultaneously to create maximum depressurization conditions.
Question 3: What does a 'spillage test' evaluate for naturally drafting combustion appliances?
- Whether the appliance is leaking gas at connections
- Whether combustion gases spill out of the draft hood into the living space (Correct answer)
- Whether the fuel supply pressure is within specification
- Whether the heat exchanger is cracked or corroded
Correct answer: Whether combustion gases spill out of the draft hood into the living space
A spillage test checks whether combustion gases exit the draft hood into the conditioned space rather than being exhausted properly up the flue.
Question 4: In pressure diagnostics, what does measuring the pressure difference between two adjacent rooms indicate?
- The insulation R-value between the rooms
- Whether duct leakage or supply/return imbalance is creating pressure differences (Correct answer)
- The thermal mass of the partition wall
- The occupant load generating CO2 in each space
Correct answer: Whether duct leakage or supply/return imbalance is creating pressure differences
Room-to-room pressure differences typically indicate supply and return air imbalances caused by duct leakage, blocked returns, or undersized return pathways.
Question 5: What is the standard correction factor (N-factor) used to convert ACH50 to estimated natural infiltration for a typical house in a moderate climate?
- 5
- 10
- 15
- 20 (Correct answer)
Correct answer: 20
A typical N-factor of 20 is used to convert ACH50 to estimated natural ACH under normal conditions (ACHnat = ACH50 ÷ 20).
Question 6: When using a combustion analyzer to test a gas furnace, what does a high CO/CO2 ratio in flue gases indicate?
- The furnace is operating at peak thermal efficiency
- Incomplete combustion is occurring, likely due to insufficient combustion air (Correct answer)
- The heat exchanger is sized correctly for the load
- Excess combustion air is diluting flue gases
Correct answer: Incomplete combustion is occurring, likely due to insufficient combustion air
A high CO/CO2 ratio indicates incomplete combustion, typically caused by insufficient combustion air, a dirty burner, or heat exchanger issues.
Question 7: What diagnostic test is used to identify specific air leakage sites in a building envelope during a blower door test?
- Duct pressurization with a Duct Blaster
- Smoke pencil or theatrical smoke to trace air movement (Correct answer)
- Infrared scan conducted at neutral pressure
- CO2 tracer gas injection test
Correct answer: Smoke pencil or theatrical smoke to trace air movement
Smoke pencils or theatrical fog machines introduce visible smoke that reveals airflow direction and velocity at leakage sites while the blower door depressurizes the building.
BPI Diagnostic Testing & Performance Evaluation 4
What is the primary purpose of performing a 'duct leakage to outside' test rather than a 'total duct leakage' test?