Upstairs too hot
I recently bought a 25-year-old house (2-story + basement colonial), and the HVAC needs some balancing. First let me describe the current installation:
The ductwork doesn't follow the typical layout I'm used to, with a branch for each floor and dampers near the furnace/ac for each branch. Instead, there is a north and sound trunk (left and right side of the house), and ductwork for the upstairs and downstairs rooms branches off from that. The only adjustable damper shuts off the south branch (both downstairs and upstairs rooms). When the previous owners finished the basement 10 years ago, vents were installed by tapping into north and south branches and installing a downward facing vent on either side of the basement. There is no air return in the basement, but there are two central return vents, one on the top floor and one on the 1st floor.
Our main problem is that the top floor is too hot, particularly the master bedroom. Since there are no master dampers, I can't simply redirect air from the lower floors to the top floor. I've tried:
(1) register booster fans (too noisy and #2 works as well)
(2) removing the register grills altogether (floor-mounted registers, so that's dangerous and unsightly)
(3) leaving the bedroom door cracked open (along with #1 and #2).
All help a bit, but what we really need is more air flowing to the upstairs. Any advice or suggestions?