Just bought a 1940's masonry construction house. House has a finished basement (cold as a meat locker), first floor (comfortable) and 2nd floor (too hot). The 2nd floor is an attic that has been converted to a master suite (with vaulted ceilings), and it's way too warm. The furnace is really old, so I'm installing a new one (with credit from seller) that has a 4-ton blower (old one is 3 ton).
The master bed (24 feet x 12 feet) has a single supply and two returns (all on the same knee wall) all at same height (wall is only 43" high and then it follows the pitch of the roof). Each return is about 6 feet either side of the supply.
Running an additional supply duct is going to be very destructive. The HVAC guy says using a 4-ton blower, putting a damper in the main trunk in basement, and splitting the supply duct in the attic will probably fix it.
Before I commit, I'd like to get some opinions on how probable a solution this is. I would have thought splitting the ducts wouldn't increase the air flow, as it's constrained by the diameter through the walls (isn't it?).
Would an inline duct fan help?