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Painting foil-faced foam board

MattJF | Posted in General Questions on

So would like to put up Dow Thermax up in my basement. I can get seconds, which are foil faced, for well less than half of new. If buying new, I would get the white version.

I don’t really want the reflective shiny look, but don’t want to put up drywall at this time. Has anyone had luck painting foil faced foam board?

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  1. JC72 | | #1

    You'll need to use an etching product and acquire the proper respirator.

  2. mackstann | | #2

    Couldn't you just lightly sand it? Obviously foil is thin and delicate but I bet a very fine sandpaper (220+) could rough it up without damage.

    1. JC72 | | #4

      Maybe. I mean who wouldn't want to manually sand ~500 sqft of foil faced board?

  3. Expert Member
    BILL WICHERS | | #3

    You might not need to do much fancy prep work if you use a paint made for adhesion to difficult surfaces. Try PPG breakthrough. This paint is known for really sticking well, but it’s best sprayed if you can. I’d do a test on one sheet and see how well it works but I think you’ll be ok.


  4. walta100 | | #5

    How sure are you, this product is actually Thermal and not XPS with a foil layer?

    As the XPS is not fire rated.

    Is the foil smooth or textured?


    1. MattJF | | #7

      The stuff I am looking at is labeled thermax, so that's easy. Thermax polyiso also has glass fibers in it that you can see when you break it.

  5. MattJF | | #6

    The tip on PPG breakthrough is what I am looking for. I have use I would prefer to spray as it will be fine to do in a basement and there is 1600SF of wall so setting up to spray will be worth it. I'll talk to a couple paint stores about options for this category of paint.

    You would not want to sand 1mil foil facing. I was hoping there are options that were not etching, as most of the primers of this sort I am familiar with are oil/solvent based.

    If the paint fails I will just put up drywall. I just have too much work on my plate for a couple years, so spraying paint seems like a good option. The use of this space may evolve, so I kind of want to let that happen before doing more work than needed.

    1. Expert Member
      BILL WICHERS | | #8

      You’ll probably need to go to a real PPG store to get breakthrough. I’ve never seen it anywhere else.

      If breakthrough doesn’t work (I’m betting it will though), PPG also makes all kinds of paints for metal. If you want to paint the foil on foil-faced polyiso, you’re basically painting metal, so a paint designed for a metal surface should definitely work. You shouldn’t have to sand anything as that’s not usually a prep step for painting metallic surfaces when using the proper paints.


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