According to nrel researchers david roberts and jon winkler moving the ducts from a vented attic to a new location inside the conditioned space will reduce electricity used for cooling by 15 to 20 and will reduce the size of the needed air conditioning equipment by 0 5 to 1 ton.
Moving ductwork from basement to attic.
All the duct work could be moved to one side of the basement possibly call someone and let him look at it.
It s one thing to blow warm air into a room but cooler air needs to be allowed out of the to make room for the warm stuff.
A drop ceiling could be fasten right below the duct work and that is about as much height as you could get.
You ll also need to provide a return path from a basement air handler or main level return to the second floor.
No thought was given in the basement to duct location.
You ll need to find a corner such as in a closet to build a duct chase to get ducts from basement to attic.
Drop sill would be hard to raise.
Even more important than that is proper location of the cold air return air ducts.
I d definitely bring the heat ducts down to the floor.
Draw a floor plan of your home including the location of the hvac air handling unit the existing ducts sprouting from it and the room or rooms in your basement where you would like to place new.
That drop sill might make it impossible.