The Remington Solar Attic Fan 20 - Watt is a combo unit, which means that the thermostat and humidistat are already built in. It is the small blue box connected to the bracket underneath the fan.
We believe as long as you use a curb mount (base) for the Remington Solar Attic Fan unit to sit on, it should be fine, but would suggest confirming with Remington Solar Inc directly on if this applies to metal roofs also. You can reach Remington Solar at 888-978-2578
Yes, the Remington Solar Attic Fan 20 - Watt can be used on flat commercial grade cool roof. The manufacturer does recommend using a curb (basically a base) mount when using this product for it to sit on.
The Remington Solar Attic Fan 20 - Watt will turn on at 80 degrees F., and will also turn on at 75% relative humidity. For additional product support, the manufacturer can be reached by calling (888) 978-2578, or by emailing [email protected].