One finaly thing these Dayton fans are high quality, super quiet , you cant hear them, I actually wonder if they are running at all or at full speed , I guess I'll play with them more when we bring down the controls.
In my experience, exhaust and gable fans like the Dayton models use a simple "on/off" type thermostat (and humidistat where present), so they're running at 100% when they're on at all.