§150.0(j) · Mechanical ventilation (whole-building and local exhaust)

# §150.0(j): Mechanical ventilation

What it requires

Every California dwelling unit requires:

• Whole-building ventilation per ASHRAE 62.2 (the standard the code adopts by reference). Default rate: 0.03 × CFA + 7.5 × (#bedrooms + 1) cfm continuous.
• Local exhaust in bathrooms, typically 50 cfm intermittent or 20 cfm continuous, vented to outside.
• Local exhaust in kitchens, typically 100 cfm intermittent or 25 cfm continuous, vented to outside (range-hood preferred over a generic kitchen exhaust fan).

Both whole-building and local fans need a sone rating low enough to satisfy occupant comfort, usually ≤ 1 sone for continuous fans, ≤ 3 sone for intermittent.

When it applies

• Newly constructed dwellings, all three categories required.
• Additions ≥ 1,000 ft² OR adding a bedroom, the whole-building rate has to be re-checked.
• Bathroom and kitchen additions, the local-exhaust requirement applies to the new room regardless of total CFA.

How we use it

The CF1R lists the design ventilation rate computed from the floor area and bedroom count you confirm. We don't pick specific fans, the designer or contractor specifies a fan model that meets both the cfm and the sone ratings, and the model is verified at field inspection (the AHJ inspector checks the fan's listed cfm against the CF1R requirement).

Common gotchas

• Recirculating range hoods aren't permitted under §150.0(j), the local-exhaust requirement is "vented to outside" by definition.
• Bathroom fans that meet cfm but exceed the sone limit fail acceptance, homeowners then keep the fan off, defeating the purpose.
• Whole-building ventilation interaction with ECM-driven ERV/HRV equipment, the rate satisfies §150.0(j) but the heat-recovery credit only counts on the performance path.