I recently bought a 2 story home that had forced hot air system from the 60's until the 90's. The owners converted to baseboard heat but left all of the ductwork and registers from the original forced hot air system. My question is...can the old ducts be used with a new AC unit? We had one person tell us that it could be done. Another told us that there are no returns up high and a completely new AC system needs to be installed which can be done through the attic. Meaning that all of the old ducts are useless. Can anyone help with a definative answer before I hire someone to do the work? I appreciate any advice and/or knowledge.