My trailer has a solar fan in the roof. I forgot exactly how many cubic feet per hour it was rated for but it sounded like plenty for my needs when I bought it. It keeps things from getting stale but not very efficient at keeping it cool and dry. It is nice to have in there while the trailer is parked in the hot sun, it does knock some of the heat out. I probably need to add some static ventilation to the trailer to help the air flow.