Your post is Dec, 2010 . . . In KY, that would be WINTER, not Summer, as your post says (?)
As I understand it, the FAN setting recirculates the interior air in a forced air system. No AC or heat is added. Honestly, a floor fan would be better in the Summer and less expensive. In the Winter, why would you run a FAN without heat anyway?
Turn off the FAN for the whole place. Get zone comfort in Summer or Winter. Save money.