- Ventilation (exhaust) capacity
Air ventilation or exhaust is calculated in cubic feet per meter (CFM). The golden rule is, one CFM per square foot of bathroom space. So, if yours is an 80 square feet bathroom, you will need a bathroom fan of 80 CFM capacity. Here is a CFM ready-reckoner:
Less than 50 square feet
50-100 square feet
Over 100 square feet:
- 100 CFM plus additional CFM per bathroom fixture:
- Toilet: 50 CFM
- Shower: 50 CFM
- Bathtub: 50 CFM
- Jet tub: 100 CFM
An alternate approach to calculating the minimum CFM requirement for your bathroom is:
Length x width x height x 0.13
Bathroom fan noise is calculated in sones rather than decibels.
For simple understanding, 1 sone equals the sound of a modern quiet refrigerator. The industry standard for contemporary bathroom fans is 1.5 sones.
Before we go to the next tip, be sure to calculate the correct CFM that your bathroom fan should have, and check that its noise level is between 1.5 and 4 sones, depending upon CFM.