ASHRAE 62.2 Whole-House Mechanical Ventilation Rate
The residential whole-house ventilation a tight house needs: Qtot = 0.03 x conditioned floor area + 7.5 x (bedrooms + 1) (ASHRAE 62.2-2019), and the continuous fan the installer must provide, Qtot minus the infiltration credit the envelope already leaks. The tighter the house tests, the smaller the credit and the larger the fan 62.2 requires - the trade-off a blower-door retest makes concrete. The conservative default is zero credit. Local kitchen/bath exhaust is separate. A sizing aid, not a 62.2 compliance certificate.
Formula and source
q_tot = 0.03 x floor_area_ft2 + 7.5 x (bedrooms + 1); q_fan = max(0, q_tot - infil_credit_cfm); verdict = q_fan > 0 (fan required) else (credit meets Qtot).
ASHRAE 62.2-2019 ยง4.1 whole-house ventilation rate (Qtot = 0.03 x Afloor + 7.5 x (Nbr + 1)) and the fan flow Qfan = Qtot - Qinf, by name; the 0.03 cfm/ft^2 and 7.5 cfm/person are the standard's rate coefficients.
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