My North Carolina garage is extremely hot, does not have a window and a room over top. In 5 years I have lost three freezers, there is no other place to put the freezer. I have tried to find a fan w ith a damper and a thermostat that could be mounted thru the wall but no luck. What can I do?
What about an attic vent fan such as this one?
It has a thermostatic control.
Separate shutters are also available such as these. They open based on the air pressure generated by the fan.
You would need to create "in" vents, preferably placed low on several walls to allow full air flow. These could be either fixed or shuttered, depending on whether you are concerned about infiltration of air in colder weather.
I've have a similar problem with my garage. Although no freezer inside. I haven't fixed it yet, but I think the solution is to install a boat cabin vent like these:
I'd install one on the side of the garage up high to exhaust the hot air. And probably provide a low down vent on the cool side of the garage to allow cool air to flow in.
As for shutting it off. You may need to make your own damper. A sheet of plywood or metal with some guides that can slide in front of the fan and vent.
There are also some fancy attic based ventilators, that may be a better option.