General thought on exhaust fans is that they are there to erase embarrassing odors from the room. That is a huge misconception. Bathrooms create a large amount of moisture and it is up to the exhaust fan to move it out.
Excess moisture can cause paint to peel and wood to warp. Left unchecked it can spur on the breeding of mold spores.
The other big misconception is that the light and fan are wired separately so that the fan can be disregarded. In actuality, the fan is wired separate so it can remain on independent from the light when the bathroom is not in use.
There are three keys to ensure proper exhaust fan use.
- Adequate fresh air. This can be achieved by allowing a 1 1/2 inch gap under the bathroom door.
- Venting surfaces should be smooth with limited bends. The vent should run outside with a flap cover, think dryer vent, to prevent drafts.
- The fan should have a proper cubic feet per minute (CFM) capacity for the room size.
To figure the CFM you will need the volume of the bathroom. To get this number multiply the length, width and height of the room. Take the volume of the room and divide it by 7.5, this will give you the CFM.
So if the volume of your bathroom is 490, your CFM is 65.3333. You can clip off the decimals and round the number up. So for the above example a fan with a CFM rating of 66 would be more than adequate air circulation for a bathroom of that size.
