Problem: Our old house has an old forced air system that unevenly heats the small rooms on the second floor and we want to try to even it out a bit, particularly as our son's bedroom is about 5-6 degrees colder than the other rooms. Part of the reason for this temperature differential is the northwest exposure of the room.
Systems: The furnace is a relatively new Trane, 2-stage, variable speed. The only hot air return on the second floor is on the far wall of an outside room. The downstairs has 3 hot air returns on the floor.
The a/c is located in the attic with runs to each 2nd floor room and 3 runs to the fairly open downstairs. In the upstairs, there is a central ceiling return in the hallway, a return in a room that connects two rooms, and a return in our son's bedroom (the room that is most problematic for heat).
Possible help: It was suggested to me that running the fan from the a/c unit would help to even out the heat in the house (If it is run continuously on fan, it runs pretty low). Will this help? Is it expensive to run it for much of the day (it's a fairly new, high-efficient Trane)?
THANKS for your help!!