I plan to finish our basement - 3 year old home with 2x4 construction which currently has two heat registers on the ceiling. Would it be better to extend the heating ducts to the outside wall and down to 8 inches above the floor or just leave the heat registers in the ceiling. My concern in extending them down the wall is that there will be heat loss to the outside wall since there will be no room for insulation behind the duct.
Answer:
I've always taken them down to near the floor and if heat loss was a conceern, I'd put 3/4" rigid foam insulation behind it if I was framing with 2X4 against the concrete. Normally though, the 2/4s were pulled 1.5" from the concrete to accommodate R-20 bats so I was able to slide 2" or high density rigid foam in there.
