I think the duct is actually fine. The duct connects to a register that is shared by two rooms. When heating, one room is gets hot, while the other is cool (not too cold). I think the problem is either insulation or windows. The hot room has 1 window, the cool room has 3 windows. I've put film over the widows, but it's still cold. Next I'll try blankets.
My house was built in the 1930s, I assume these ducts were installed when the home was built. This duct goes from the supply plenum in the basement to the 2nd floor master bedroom. The best I can measure, it's 10" x 4" .
If you look in the photo below, the duct work is comprised of several small sections of metal. They look to be about a foot long each, with some overlap between sections. Note: the light source is a ribbon of LEDs that I lowered down the duct.
My concern is that the metal is buckled in several spots and is coming away from the wall, and I'm concerned that it's leaking air pressure. Presumably, the outside of the duct is the wall studs and lath and plaster.
- Should I actually be concerned about the buckling metal? Is there really that much air pressure being lost?
- Is there anything I can do to repair this?
I had a couple of ideas of some repairs.
- I could try to reattach the metal to the walls with sheet metal screws from the inside. This would require drill extensions and an 90 degree adapter ... and it would probably be pretty difficult to do.
- I could try to drill through the walls on the outside of the ducts and secure the metal with toggle bolts.
- I could try to fill the gaps with spray foam gap filler, but that could backfire if it expands and pushed the ducts out further.
- I could try to run flex ducts inside the old duct work, or maybe duct board since there aren't any rectangular duct products.