CBD Ventilation & Mechanical Systems 1 — Questions and Answers
Question 1: According to ASHRAE 62.2, what is the minimum recommended intermittent exhaust rate for a residential bathroom?
- 20 CFM
- 50 CFM (Correct answer)
- 75 CFM
- 100 CFM
Correct answer: 50 CFM
ASHRAE 62.2 specifies a minimum of 50 CFM for intermittent bathroom exhaust ventilation to adequately remove moisture and odors.
Question 2: Which organization certifies and rates residential exhaust fans for airflow performance and sound levels?
- ANSI
- HVI (Home Ventilating Institute) (Correct answer)
- ASHRAE
- NKBA
Correct answer: HVI (Home Ventilating Institute)
The Home Ventilating Institute (HVI) is the industry body that certifies exhaust fans for both airflow (CFM) and sound (sone) performance.
Question 3: A bathroom exhaust fan rated at 1.0 sone is best described as:
- Extremely loud, like a vacuum cleaner
- Equivalent to normal conversation
- Very quiet, comparable to a library (Correct answer)
- Moderate, like background office noise
Correct answer: Very quiet, comparable to a library
A 1.0 sone rating is very quiet—equivalent to a quiet library—making it ideal for high-end bathroom installations where noise is a concern.
Question 4: What is the maximum recommended length of flexible exhaust duct allowed when connecting a bathroom exhaust fan to rigid ductwork?
- 2 feet
- 4 feet
- 6 feet (Correct answer)
- 10 feet
Correct answer: 6 feet
Most codes and manufacturer guidelines limit flexible duct connectors to 6 feet to minimize airflow restriction and moisture accumulation.
Question 5: Which exhaust fan control provides the most effective moisture management in a bathroom by responding directly to humidity levels?
- Manual wall switch
- Timer switch
- Humidity-sensing switch (Correct answer)
- Occupancy sensor
Correct answer: Humidity-sensing switch
A humidity-sensing switch automatically activates the fan when relative humidity rises above a set point, directly addressing the source of moisture buildup.
Question 6: When sizing an exhaust fan for a bathroom using the HVI rule-of-thumb method, what CFM per square foot is recommended for rooms with 8-foot ceilings?
- 0.5 CFM/sq ft
- 1.0 CFM/sq ft (Correct answer)
- 1.5 CFM/sq ft
- 2.0 CFM/sq ft
Correct answer: 1.0 CFM/sq ft
HVI recommends 1 CFM per square foot of bathroom floor area for standard 8-foot ceilings as a quick sizing method.
Question 7: Bathroom exhaust fans must always terminate to the exterior of the building because discharging into an attic will:
- Cause the fan motor to overheat
- Create moisture damage and potential mold growth in the attic (Correct answer)
- Violate electrical code requirements
- Reduce the fan's CFM rating
Correct answer: Create moisture damage and potential mold growth in the attic
Discharging warm, humid bathroom air into an attic causes condensation on framing and insulation, leading to moisture damage and mold growth.
CBD Ventilation & Mechanical Systems 1
According to ASHRAE 62.2, what is the minimum recommended intermittent exhaust rate for a residential bathroom?