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Insulation inside air returns

2982 Views 11 Replies 4 Participants Last post by  Mijotter
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.
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Why would you want to insulate a return duct?? I don't see why you couldn't put in some XPS but don't see the point of doing so.
Only supplys need to be insulated.
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.


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Anyone? Would like to get this started today.
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
I wouldn't do it. No reasonable return (pardon the pun) to justify the expense and effort.
You planning on replacing metal panning with duct board or using pieces of duct board to insulate .
replacing the sheet metal with Thermopan ductboard.
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.
Why is that? The reason i'm doing this is because it's old, filthy, and I'm sound proofing the basement. Will xps in that area hurt or not?
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