How to Upgrade to a Bigger Bath Fan
Q: Our bath fan doesn't keep moisture off the walls, even if we open a window. Do we need a bigger
--Bill Jackson, Olyphant, Pa.
Matt Tomis of Tomis Electrical Contractors replies: You shouldn't have to open a window! Maybe the
fan is clogged with dust. Take off its cover and vacuum out its housing. And, if you can get to the
fan's duct, make sure it isn't pinched or blocked. If that doesn't help, it's probably time for a new
You want one with a cubic-feet-per-minute (cfm) rating
that's high enough to pull all the air out of your
bathroom in 7½ minutes. To determine the fan's
minimum cfm, divide your bathroom's volume by 7.5.
Go with a higher cfm if the duct run exceeds 20 feet or
has more than one elbow. Also, put the fan on a timer
so that it runs for at least 20 minutes after you finish
showering and exhausts all the moisture.
The fan I'm installing here has a built-in timer. Finally, compare sone ratings; the lower the number,
the quieter the fan. It has an important job, but nobody wants to hear it working.
Shown: WhisperGreen LED 80-cfm ventilation fan (model FV-08VKME3) with night light and motion