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Community and Q&A

Can I use EPS rigid polystyrene insulation board to insulate interior window?

toddsmith | Posted in Energy Efficiency and Durability on

For my window, I put clear bubble wrap on first adhering it to the window with vinegar and water to stick – then put foam board flush ontop to insulate the window. Will this cause cracking of the glass in the winter at all? Will there be off gas from the foam board insulation to worry about?
Please Help,
Thank You. TD

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  1. Expert Member
    Dana Dorsett | | #1

    There is no outgassing from EPS, but it is a fire/smoke hazard if left exposed.

    It's not clear from the description where the EPS is being applied- is it sash-frame-only, or is it covering the bubble pack?

  2. toddsmith | | #2

    Both bubble wrap then the eps foam board is applied directly on the window glass.

    1. Expert Member
      Dana Dorsett | | #3

      >"Both bubble wrap then the eps foam board is applied directly on the window glass."

      I'm still having a hard time parsing this...

      Does this mean there is bubble wrap on one side (presumably the interior, indoors), and the EPS is being applied to the exterior (outdoor) surface of the glass?

    2. Expert Member
      BILL WICHERS | | #4

      It sounds like this will be a sandwich with the inside glass pane on one side, Then the bubble wrap, then a sheet of EPS, all on the interior of the window. I don’t see any problem doing this, but I would suggest that just using a thicker piece of EPS and skipping the bubble wrap will be less work and less potential mess to remove. If you cut the EPS sheet carefully, you can probably get it to stay put with a simple friction fit and not need any water/vinegar to adhere it to the glass.


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