To determine the correct size bath fan for your bathroom, you need to calculate the required airflow in Cubic Feet per Minute (CFM). Here's how, based on information from the Home Ventilating Institute (HVI):
The required CFM depends on your bathroom's size and the fixtures it contains.
Method 1: Based on Bathroom Size
-
Less than 50 sq. feet: 50 CFM
-
50-100 sq. feet: 1 CFM per square foot of floor space.
- Example: For a bathroom that is 60 sq. feet, you would need a 60 CFM fan.
Method 2: Based on Bathroom Fixtures (for bathrooms larger than 100 sq. ft.)
If your bathroom is larger than 100 square feet, calculate the CFM requirement based on each fixture:
| Fixture | Minimum Ventilation (CFM) Required |
|---|---|
| Toilet | 50 CFM |
| Shower | 50 CFM |
| Bathtub | 50 CFM |
| Jetted Tub | 100 CFM |
- Example: A large bathroom has a toilet, shower, and bathtub. The required CFM would be 50 (toilet) + 50 (shower) + 50 (bathtub) = 150 CFM.
