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Using Polyethylene foam sheets for camper insulation

Campervan_Mike | Posted in General Questions on

I’m building a camper van from a Dodge Promaster and have not seen anyone use Polyethylene Foam Sheets as insulation. I’m wondering why that is the case since this material would bend to the shape of the van wall (where EPS, Polyiso, etc… aren’t as flexible in the same way).

I’m guessing it’s a “cost-per-R-Value” concern since a 4’x8′ sheet of 1″ Polyethylene Foam costs over $80 whereas EPS and polyiso are under $20

Is there a VOC concern with polyethylene foam (I’ve read it’s very safe)?

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Replies

  1. Expert Member
    Zephyr7 | | #1

    If it’s the material I’m thinking of, it’s pretty flammable. I would not use a material not rated for the purpose in this application. Remember that there have been numerous fatal night club fires because the clubs decided to “save money” using packaging foam as sound absorbing material on the walls, instead of the correct material that has fire retardants in it. Be careful.

    Bill

  2. Campervan_Mike | | #2

    Well, the polyethylene isn't a "money saving" decision since it is about 4 to 5 times the price of other options... I did notice that there is no flame retardant in the foam I'm looking at - I assumed that was because it is not very flammable but i could be wrong, I'll try to light a small piece on fire and see what happens.

    Here's a link to the foam's product page:
    https://www.thefoamfactory.com/closedcellfoam/polyethylene.html

    1. Expert Member
      Zephyr7 | | #6

      That stuff IS flammable. I would NOT use it. Just because it isn’t cheap doesn’t mean it’s a better product for this application. Also, just because other do it yourselfers are using it doesn’t mean it’s a good idea either. I have seen plenty of expensive and/or dangerous problems caused by people using improper materials. I have been contracted to correct such issues in a number of commercial facilities, and it’s usually expensive.

      I’d try this place: https://www.aircraftspruce.com/menus/cs/insulation.html
      These guys sell to aircraft people. There are people who build and “renovate” aircraft. Some of their requirements are similar to yours (needing flexible insulation that is fire resistant). The materials that are acceptable for use in aircraft are usually pretty good, since they have to meet a lot of standards or the airplane isn’t allowed to fly. The FAA is FAR more picky than building departments! Remember that if your airplane starts having problems, you can’t pull over and pop the hood to check things out...

      Bill

  3. Joshua Van Tol | | #3

    Mike, does that product even have a rated R-value per inch? Also, it says closed cell, but I wonder how air tight it is? Moist air migrating through the foam to the cold metal skin of the vehicle is a concern in the winter.

  4. Campervan_Mike | | #4

    According to the following page 1" offers an R-Value of 3.2
    https://www.foambymail.com/polyethylene-foam-sheet.html

    And I would think a closed cell foam would actually create a vapor barrier as the air bubbles are not connected to each other - kind of like a solid piece of plastic with bubbles in it.

    Solid Polyethylene is what some cutting boards are made of - a very tough material

    Polyethylene Foam: If you've ever purchased something that is fairly heavy like an old tube stye TV the packaging material used was sometimes polyethylene foam - it's basically squishy styrofoam that is very durable, it's even somewhat difficult to tear a piece in half. "It is also impervious to mildew, mold, rot, and bacteria with superior chemical and grease resistance."

  5. George Smith | | #5

    Some in the van camper community use a product called Thinsulate. I don't have a url, off hand, but Google is your friend.

  6. DCContrarian | | #7

    Two part closed cell spray foam would cost less and give better insulation and air seal. I think it would even be easier to apply. You can buy kits online. Some even use nitrogen as the propellant.

  7. George Smith | | #8

    Spray foam has caused "oil canning" on a number of vans. Probably a good idea to avoid it.

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