Originally Posted By: demarpaint
Why can't you use 1/2" green board? Then prime it with Bullseye 123 and top coat with a good kitchen and bath paint. If 1/2" green board is out of the cards, as mentioned proper ventilation is a must. Then after the sheet rocking is done use a coat of 123 primer, and top coat it with 2 coats of kitchen and bath paint. Avoid oil primers and oil paints in a bathroom prone to mildew.
OP, can you use "shims" to bring the studs to the depth you need for the 1/2" green board?
also what Demarpaint said (he has 30+ years as a pro painter...)
i think they make either bathrooms fans with humidity sensor incorporated ($$) or switches with humidity sensor and timer incorporated...or you wire it to the bathroom light