Mermaid, GOOGLE

Greenhouse Ventilation

for the technical information on air flow requirements. As to fans I
have tried MANY for my business of carwashing to cool myself in the
pump rooms. By far the best was a carpet dryer. It was plastic housed
and designed for damp enviroments. Look here

www.bettymills.com/.../ product/ZEAG9707.JPG

for an example. These are sold on Ebay all the time at a reasonable
price. They are just so easy to use compared to other fans and really
move a lot of air.
Best Regards
Joe T
Baytown, TX