HERS Ventilation & Indoor Air Quality 1 — Questions and Answers
Question 1: Which ASHRAE standard governs minimum mechanical ventilation requirements for residential buildings rated under the HERS program?
- ASHRAE 62.1
- ASHRAE 62.2 (Correct answer)
- ASHRAE 90.1
- ASHRAE 55
Correct answer: ASHRAE 62.2
ASHRAE 62.2 is specifically the ventilation standard for low-rise residential buildings, which applies to homes evaluated under the HERS rating system.
Question 2: Using the ASHRAE 62.2 formula, what is the minimum required whole-building mechanical ventilation rate for a 1,500 sq ft home with 3 bedrooms?
- 30 CFM
- 45 CFM (Correct answer)
- 60 CFM
- 75 CFM
Correct answer: 45 CFM
The ASHRAE 62.2 formula is 0.01 × floor area + 7.5 × (bedrooms + 1) = 0.01×1,500 + 7.5×4 = 15 + 30 = 45 CFM.
Question 3: In a tight home with a blower door result at or below 3 ACH50, ASHRAE 62.2 requires mechanical ventilation primarily to:
- Reduce peak cooling loads
- Dilute indoor pollutants and maintain acceptable indoor air quality (Correct answer)
- Pressurize the building envelope against moisture drive
- Satisfy fire code egress requirements
Correct answer: Dilute indoor pollutants and maintain acceptable indoor air quality
Mechanical ventilation in tight homes ensures sufficient fresh air exchange to dilute pollutants like CO2, VOCs, and moisture that accumulate when natural infiltration is insufficient.
Question 4: Per ASHRAE 62.2, the measured airflow of a mechanical ventilation system must be within what tolerance of the design rate to be considered compliant?
- ±5%
- ±10% (Correct answer)
- ±15%
- ±25%
Correct answer: ±10%
ASHRAE 62.2 requires that measured ventilation airflow be within ±10% of the design airflow rate to confirm the system is performing as intended.
Question 5: Which of the following ventilation system types provides the greatest control over both supply and exhaust airflow rates in a residence?
- Exhaust-only ventilation
- Supply-only ventilation
- Balanced ventilation (Correct answer)
- Natural ventilation through operable windows
Correct answer: Balanced ventilation
Balanced ventilation systems control both supply and exhaust airstreams independently, providing the most precise management of ventilation rates and building pressurization.
Question 6: Under ASHRAE 62.2, which type of local ventilation is required in addition to whole-building mechanical ventilation?
- Whole-house dehumidifier
- Spot ventilation for kitchens and bathrooms (Correct answer)
- Central air filtration with MERV-8 filter
- Passive stack ventilation in the attic
Correct answer: Spot ventilation for kitchens and bathrooms
ASHRAE 62.2 Section 5 requires separate local exhaust ventilation (spot ventilation) for kitchens and bathrooms to remove source pollutants, independent of whole-building requirements.
Question 7: Per ASHRAE 62.2, kitchen exhaust fans with airflow ratings at or below 400 CFM must have a maximum sound rating of:
- 1 sone
- 2 sones
- 3 sones (Correct answer)
- 5 sones
Correct answer: 3 sones
ASHRAE 62.2 Section 5.1 limits kitchen exhaust fan noise to a maximum of 3 sones for intermittent fans rated at or below 400 CFM to encourage occupant use.
HERS Ventilation & Indoor Air Quality 1
Which ASHRAE standard governs minimum mechanical ventilation requirements for residential buildings rated under the HERS program?