How much whole-house ventilation does ASHRAE 62.2 require for a 2000 sq ft, 3-bedroom house?

Q: Does this number include bathroom and kitchen exhaust fans?

No. This is only the continuous whole-house ventilation rate. ASHRAE 62.2 requires local exhaust separately: 50 CFM intermittent (or 20 CFM continuous) in each bathroom and 100 CFM intermittent in kitchens, which you size in addition to this figure.

Q: Why does the calculation use bedrooms instead of actual occupants?

ASHRAE 62.2 uses bedroom count as a standardized proxy for occupancy, assuming the number of occupants equals bedrooms plus one. This avoids guessing future occupancy and is why the occupant term is 7.5 x (Nbr + 1). Leakier homes may also get an infiltration credit under the 62.2-2019 infiltration adjustment, which this tool does not apply.

Question

How much whole-house ventilation does ASHRAE 62.2 require for a 2000 sq ft, 3-bedroom house?

Accepted Answer

Using the ASHRAE 62.2-2019 formula Qtot = 0.03 x Afloor + 7.5 x (Nbr + 1), a 2000 sq ft, 3-bedroom home needs 0.03 x 2000 = 60 CFM from floor area plus 7.5 x 4 = 30 CFM from occupants, for 90 CFM of continuous airflow. That is the continuous whole-house rate before any local exhaust is added.

How much whole-house ventilation does ASHRAE 62.2 require for a 2000 sq ft, 3-bedroom house?

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