or a gable-mount fan (for attics) put one of those in the ceiling, and BAM! They can be had for under $50, you'll have to either modify or eliminate the temp controller if it has one, but they are big (15" and up) and I've used them in darkrooms for years.
4x5 Reviewed by 4x5 on . help!!!!! my extraction fan has just died,anybody know if a bathroom extractor fan would do the same job????? Rating: 5