The controller has a range of up to 99 degrees C or 210 degrees F so it works controlling an attic fan. Note that the contacts are rated at 10 amps. A fan is an inductive load so you should probably keep the maximum fan size of about 5 amps to get good life out of the contacts. If you need to use a larger fan you could use a relay to control the fan using the controller contacts to actuate the relay coil.