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AndyA7317 | Posted in General Questions on

I live in upstate New York and am remodeling my family room. It is adjacent to my garage. When I removed the ceiling tiles I can now see what my walls are insulated with. It looks like it is foam board with grey foil on it. I am not sure how thick it is. The wall studs are 2×4. If there is enough room for the batt insulation can I just install the batts over the foam board or should I remove the foam boards and just install my batts? Thanks in advance for any replies.

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  1. Expert Member
    Dana Dorsett | | #1

    "Upstate" ranges from US climate zone 4A (Westchester county) to US climate zone 7A (at altitude in the Adirondacks). Most of upstate NY is either zone 5 or 6. (see: ) Local climate matters- can you be a bit more specific?

    We have to know more about the stack-up of the assembly to know whether or how much batt insulation can be safely installed under or over the foam board, on either the walls or ceiling. Odds are pretty good that the foam is polyisocyanurate, but the color & texture of the foam itself would be a clue.

  2. AndyA7317 | | #2

    Sorry Dana. I missed the map when posting. I am in climate zone 6A. I haven't demoed the walls yet. Currently, they are knotty pine and will be replaced with drywall. I am not 100% sure of the texture or color or thickness of the foam board as all I was able to see last night was the grey foil backing. Sorry I can't be more specific at this time as I am on lunch break and not at home. If it helps, I can get a better idea tonight when I get home and can check more closely.

  3. Expert Member
    Dana Dorsett | | #3

    What is the exterior sheathing & siding?

  4. AndyA7317 | | #4

    The house is vinyl sided. Sheathing is plywood. No insulation on exterior that I am aware of. My family room is 10 x 20. The ten foot walls are exterior. The 20 foot wall is adjacent my attached garage. The garage walls are not insulated - just the ceiling. I guess one of my main concerns was condensation if I install batts over the foam board. Would this be a possibility? I am not the most knowledgeable when it comes to this so I apologize if any of these questions are or should be obvious!

  5. GBA Editor
    Martin Holladay | | #5

    I'm confused.

    1. Is the wall you want to insulate the wall that divides your house from the garage, or an exterior wall?

    2. Where is the rigid foam? Is it (a) Continuous rigid foam on the interior side of the studs, or (b) Continuous rigid foam on the exterior side of the studs, or (c) Strips of rigid foam inserted in the stud bays?

    3. If (c), are these strips (d) Installed toward the interior side of the stud bays, or (e) Installed toward the exterior side of the stud bays?

  6. AndyA7317 | | #6

    Hi Martin. Sorry for the confusion. These are strip of foam board between the interior studs so I am sure way below code. The room is anyways child. I want to insulate all three of the walls.

  7. AndyA7317 | | #7

    The room is always cold. Autocorrect strikes again.

  8. user-1072251 | | #8

    Have you done a blower door test? There may be cold air leaking into the room which is cooling it down, but leaks can be hard to find. What is under the room?

  9. GBA Editor
    Martin Holladay | | #9

    Your options depend in part on the thickness of the rigid foam pieces. If they only fill up half the depth of the stud bays, or less than half, it should be possible to fill the remaining depth of the stud bays with dense-packed cellulose insulation. The dense-packed cellulose would reduce air leakage and improve the R-value of the walls.

    Call up a cellulose insulation contractor to discuss your options.

  10. AndyA7317 | | #10

    Martin and Bob,
    Thanks for your replies. I was a little busy over the weekend. The room is under my daughter's bedroom and our upstairs bathroom and hallway. I will check with a contractor and see what they recommend. If they can't work with it I will just remove the old foam slats and insulate with some R15 wool comfortbatts and vapor barrier it. It will be a huge improvement on what is there. I would like to thank everyone for taking the time out of their days to give me advice. It is much appreciated.

  11. GBA Editor
    Martin Holladay | | #11

    What makes you think that the wall between the house and the garage is a concrete wall? I assumed it was a wood-frame wall.

  12. AndyA7317 | | #12


    It is a wood-frame wall so would my plan on removal and replacement with the wool insulation be sufficient?

  13. GBA Editor
    Martin Holladay | | #13

    There are lots of ways to insulate a wall, and whether any approach is "sufficient" depends on your goals.

    For a wall separating a house from an attached garage, the two most important factors are (a) the insulation should meet local building code requirements, if there are any, and (b) the wall should be as airtight as possible (to reduce the chance that VOCs and other nasty substances might enter the house and affect the indoor air quality).

  14. dickrussell | | #14

    If you take out the old foam slats, then you don't want to replace with a porous insulation. You need to treat that wall next to the garage as a basement wall. If you are redoing that wall, do it right, and remove the stud framing also. Use rigid insulation against the concrete, then fasten the old studs over the foam, flat side against the foam with shallow electrical boxes for outlets. Cover the studs with sheetrock and finish as desired. See this link:

    [Edit, per later comment by Martin]: Oops, I did incorrectly assume that the wall was concrete, not framed.

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