We are gutting the second floor of a turn-of-the century "American Four-Square" home. We have discovered the furnace ductwork runs adjacent to the old central chimney line (from an old stove furnace in the basement), straight up through the second floor into the attic, from which point the ductwork was routed into each of the four second floor rooms by way of ducts that come out of each rooms' ceiling. My question here, is can this system be made to be any more efficient? Is our only option to run new ductwork through a new "subfloor" of our second level? Is this a costly and difficult task?
In your climate, heating ducts in the attic is not good for efficiency. Getting warm to go anywhere but up takes a good blower system, and warm air works best when introduced at the floor level. During construction is the only time that it is easy to change the routing, so this would be the time. Have the system analyzed by a HVAC expert. The other alternative is to run insulated ducts in the attic.