William W. Plummer wrote:

If you install a fan, connecting it to the bathroom lights is fine.

Better yet, connect it to Herbach and Rademan's (800) 848-8001
http://www.herbach.com nice brass $4.95 Navy surplus humidistat
(or is that a DEhumidistat? :-), their item number TM89HVC5203,
with a 20-80% range, a 3-6% differential, and a 7.5A 125V switch
that can be wired to open or close on humidity rise.

...The fan doesn't have to run very long to get the relative humidity
down to the point where condensation won't be an issue. Ex: My bathroom
is 10' x 4' by 8' which is 320 cu ft. So, a 100 cfm fan will cut the
humidity to 50% in 3 minutes.

There's a lot missing before your "So" :-)

Nick