True, I'm no proponent of using an intake fan, but I do realize there are times that one may be necessary. If you have good exhaust, a simple intake hole, (or two) the same size as the exhaust hole is sufficient.

I have not had any experience in going hydro, and thusly don't want to represent that these 'techniques' will work that way. I try never to comment on techniques I've never personally tried before.
The main thing I'd worry about, tho...is how to keep the reservoir cooled enough not to harm the roots.

Have you thought of using a light mover?
Rusty Trichome Reviewed by Rusty Trichome on . Dealing with heat issues in the desert... Below is what I do for my soil grow during our hot summer months in the southwestern desert. I have never grown hydro, so am unable to verify any of this for anything other than soil grows. My flowershed is an outdoor shed approx 8' x 12' x 8' tall, of which a quarter if it is for growing. (no, it's not a metal shed) In my humble (sometimes) opinion, "must keep temps below 80" is a guideline, especially appropriate for beginners. -However- Being anal about it is truly unnecessary. Rating: 5