Hi, I am finishing my basement, and am planning to drywall the ceiling where the return plenum currently is. The return uses the 1st floor subfloor and the joists, with sheetmetal on the bottom. As it is now, when walking around upstairs, I get some 'oil can' noises from the return plenum, just slight noises, nothing too bad...
I am wondering if it is advisable to remove the lower sheetmetal before I cover the joists with drywall. My reasoning for doing this is to reduce the oil can like noise that can be heard, and also make the ceiling as flat as possible. I would only remove the sheetmetal that would be replaced with drywall, and ensure that the end caps will seal well against the drywall.
I am not planning on using furring strips, because the joists look to be level enough and on center.
Even if you caulk all those joist. Good chance that the drywall will come loose just enough to draw in air from the rest of the joist space.
Since your rim board probably isn't sealed air tight. It will draw in fresh outside air, and pressurize your house, and raise your heating bill.