This is the 1300 CFM exhaust fan in our detached garage. Note the thermostat on the right.
Our new home is lined with SucraSeal - a liquid foamed in place insulation. The roof has an R60 rating and the walls are R30. But our garage is a separate building with no insulation at all. Therefore - it can get very hot in the garage with the doors are closed.
Yesterday - I used my thermometer gun and it said the roof plywood was 112 degrees. So I built a plywood box in the eave over the vent and installed an exhaust fan. It is an electric fan that draws 2 amps of power (about 2 cents an hour when running) - and moves 1300 cubic feet of air a minute. In 7 minutes it can drain the garage of all of its stale air. The fan has a thermostat that I have set to turn on at 95 degrees. So when the air in the attic of the garage gets to 95 - the fan goes on - and cools the garage.
Of course if the air outside is 95 degrees - the garage is never going to get below that temperature. You are simply sucking fresh air from outside - to the inside.
When the temperature gets above 95 degrees - the fan goes on automatically.
You can set the thermostat to go on at any temperature.
The attic in our detached garage is 6 feet high - 16 feet wide - and 36 feet long. It is a great place to store excess lumber or other things you do not need ready at hand. Presently access to the attic is a ladder.
The fan is hard wired to the circuit box in the garage. There are 4 - 120 volt circuits and 1 - 220 volt circuit. The 220 volt circuit is for a future electric car charger.
The exhaust fan is directly behind the white vent in the garage roof eave.