Ventilation CFM Calculator (ASHRAE 62.2)
About ASHRAE 62.2 Ventilation Standard
ASHRAE 62.2 is the US standard for residential mechanical ventilation. The formula is: Qfan = 0.01Af + 7.5(Nbr+1), where Af is the conditioned floor area in sq ft and Nbr is the number of bedrooms. This ensures minimum fresh air for healthy indoor air quality.
Compliance with ASHRAE 62.2 is required by the International Residential Code (IRC) and many state building codes. Systems can be exhaust-only, supply-only, or balanced (HRV/ERV).
Frequently Asked Questions
What is the ASHRAE 62.2 formula?
Qfan = 0.01 × Af + 7.5 × (Nbr + 1). Af = conditioned floor area in sq ft, Nbr = number of bedrooms. For a 2,000 sq ft home with 3 bedrooms: 0.01×2000 + 7.5×4 = 50 CFM.
Does my home need ASHRAE 62.2 compliance?
If built after 2012, your local building code likely requires ASHRAE 62.2. The International Residential Code (IRC) adopted it in 2012. Check with your local building department.
What type of ventilation system should I use?
Exhaust-only (bathroom fans running continuously): simplest, $200-500. Supply-only: brings in filtered fresh air. Balanced (HRV/ERV): best efficiency but $2,000-5,000 installed. HRV is best for cold climates, ERV for humid climates.