My (fairly new to me) home is located in the pacific northwest and built around 1880. I have forced air heating (furnace in basement) and AC (both are adequately sized for the entire home) which are great on the first floor. Very little comes out of the vents on the second floor. I know the main problem is that the first floor has 6 ducts coming off the trunk and the second floor has one. The second floor duct also takes two 90 degree turns on its way to the attic where it splits into 3 ducts. I am considering placing motorized dampers at the trunk on all of the ducts and adjusting them when I want to heat/cool the 2nd floor. Any idea on the likelihood of this working? If not, do you have any suggestions?