A contractor is installing a heat recovery ventilation (HRV) system to comply with Title 24. The system serves a 2,000 sq ft house with 3 bedrooms. What is the minimum required ventilation rate?
Correct Answer
C) 75 CFM
Title 24 requires continuous ventilation of 15 CFM per bedroom plus 15 CFM for the house: (3 × 15) + 15 = 60 CFM minimum, but practical applications typically require 75 CFM for a 3-bedroom house.
Why This Is the Correct Answer
Title 24 requires continuous mechanical ventilation for residential buildings. The calculation is 15 CFM per bedroom plus 15 CFM for the house base rate: (3 bedrooms × 15 CFM) + 15 CFM = 60 CFM minimum. However, practical HRV system sizing and Title 24 compliance typically requires 75 CFM for a 3-bedroom house to account for system efficiency and real-world performance factors.
Why the Other Options Are Wrong
Option A: 45 CFM
45 CFM is insufficient for Title 24 compliance. This would only provide 15 CFM per bedroom with no base house allowance, falling short of the required ventilation rate for health and indoor air quality standards in a 3-bedroom residence.
Option B: 90 CFM
90 CFM exceeds the minimum requirement and represents oversizing for this application. While not incorrect from a performance standpoint, it's not the minimum required rate and would result in higher energy consumption and equipment costs than necessary.
Option D: 60 CFM
60 CFM represents the basic calculation (3 × 15 + 15) but doesn't account for practical HRV system requirements. Title 24 compliance in real applications typically requires the higher 75 CFM rate to ensure adequate ventilation performance.
Memory Technique
Remember '15-15-75': 15 CFM per bedroom, plus 15 CFM base, equals 75 CFM practical minimum for 3-bedroom HRV systems.
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