To add central AC to our house, the previous owners had their contractor run a line above the finished attic ceiling and drop ducts so that they’d go through closets on the second floor to get to the first floor. The result is a finished attic with two 24″x24″ drywalled columns in the middle of it.

I’d like to route the ductwork over behind the kneewalls and then back to connect with the original work  (below the floor level). This would get rid of these columns but would add at least 15-20′ to each run plus three additional 90 degree angles. I would add duct fans to compensate for all this.

I guess what I need to know before embarking on this is: will the fans compensate for the additional length/turns? And – is there a better way?

Thanks!