I have a split level house and right now my furnace is in the utility room directly below my kitchen. The duct runs up the full height of the house and is partially blocking the doorway into my kitchen which I would like to widen. Does the return duct have to run all the way to the attic and finish in the ceiling? Would it be possible to end the return on a main floor wall and remove the duct that runs through the main floor? Right now the duct is in such a inconvenient location in middle of the house. Thanks in advance for the advice.