I'm replacing my old sheet metal returns in the ceiling with Thermopan duct board. My question is, can I place xps rigid foam board in the rim joists inside the return before putting the new duct boards up? I would seal them with Great Stuff or is that not advisable.
not insulate the duct themselves. just the rim joist that the plenum buts up to. This is a basement ceiling btw. I have all the other open rim joists properly insulated and was just wondering if I should do the same that the plenums butt up against in the ceiling as they follow the ceiling joist.
Looks like panning on bottom of joist.If this panning is going all the way to the outside bond, then chances are there are openings at the exterior walls for R/A going to upper floors.So trying to put insulation in the joist space around the bond probably wont be possible without covering cutouts.
Correct but there is about 3 inches of space between the cutout and the outside wall where 2"xps could feasibly go. I just need to know if it will helop with insulation at all and that kind of insulation will be ok in a return(health reasons
If it were me I would use pieces to insulate the bond and leave the metal up.Or buy couple cans of great stuff and foam the space for a better air seal.
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