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Tuesday, September 09, 2014

Garage Attic Fan Keeps Things Cool

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. 

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