To calculate how many CFM of airflow is required to properly ventilate any room in your home, use the following calculation.
For an 8 foot ceiling take the square footage of the room and multiply it by 1.1. (Example – 10' x 10' room with 8' ceilings: 10' x 10' = 100 square feet x 1.1 = 110 CFM’s)
For any ceiling over 8 feet, take the height of the ceiling and multiply by .1375. Take this figure and multiply by the square footage of the room. This will equal the recommended CFMs. (Example – 10' x 12' room with 9' ceilings: 9' x .1375 =1.24 x 120 square feet = 149 CFMs.)
Both calculations will give you the minimum recommended CFM
Bathroom fan sizing chart
Bathroom (to achieve 8 ACH as per HVI) |
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Equivalent duct length |
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Sq ft |
20 feet |
40 feet |
60 feet |
80 feet |
100 feet |
30 |
FV-05VQ |
FV-05VQ |
FV-05VQ |
FV-05VQ |
FV-05VQ |
40 |
FV-05VQ |
FV-05VQ |
FV-05VQ |
FV-05VQ |
FV-05VQ |
50 |
FV-05VQ |
FV-05VQ |
FV-08VQ or FV-08VQL |
FV-08VQ or FV-08VQL |
FV-08VQ or FV-08VQL |
60 |
FV-08VQ or FV-08VQL |
FV-08VQ or FV-08VQL |
FV-08VQ or FV-08VQL |
FV-11VQ or FV-11VQL |
FV-11VQ or FV-11VQL |
70 |
FV-08VQ, FV-08VQL, |
FV-08VQ, FV-08VQL, |
FV-11VQ, FV-11VQL, |
FV-11VQ, FV-11VQL, |
FV-11VQ, FV-11VQL, |
80 |
FV-11VQ, FV-11VQL, |
FV-11VQ, FV-11VQL, |
FV-11VQ, FV-11VQL, |
FV-15VQ or FV-15VQL |
FV-15VQ or FV-15VQL |
90 |
FV-11VQ, FV-11VQL, |
FV-11VQ, FV-11VQL, |
FV-15VQ or FV-15VQL |
FV-15VQ or FV-15VQL |
FV-20VQ or FV-15VQ or |
100 |
FV-11VQ, FV-11VQL, |
FV-15VQ or FV-15VQL |
FV-15VQ or FV-15VQL |
FV-20VQ or FV-15VQ or |
FV-20VQ or FV-15VQ or |
140 |
FV-15VQ or FV-15VQL |
FV-20VQ |
FV-20VQ |
FV-20VQ |
FV-20VQ |
180 |
FV-20VQ or FV-11VQ (x2) |
FV-20VQ or FV-11VQ (x2) |
FV-20VQ or FV-11VQ (x2) |
FV-20VQ or FV-11VQ (x2) |
FV-30VQ or FV-20VQ (x2) or |
240 |
FV-20VQ or FV-11VQ (x2) |
FV-20VQ or FV-11VQ (x2) |
FV-30VQ or FV-20VQ (x2) or |
FV-40VQ or FV-20VQ (x2) or |
FV-40VQ or FV-20VQ (x2) or |
300 |
FV-40VQ or FV-20VQ (x2) or |
FV-40VQ or FV-20VQ (x2) |
FV-40VQ or FV-20VQ (x2) |
FV-20VQ (x2) |
FV-20VQ (x2) |