This insulation says it cannot remain exposed and requires a "15-minute thermal barrier." I've looked around and found this stuff that says it provides a 15-minute thermal barrier but I've not found details about what a 15-minute thermal barrier actually is.

What is a 15-minute thermal barrier?

Does drywall provide such a barrier?

  • A barrier that will prevent the heat getting through for 15 minutes or more.
    – Solar Mike
    Sep 2, 2022 at 20:49
  • A thermal barrier is something that stops/slows heat from going though. Something like drywall or a heat shielding covering/paint.
    – crip659
    Sep 2, 2022 at 20:49
  • 2
    The barrier is to prevent the heat of a fire from penetrating the wall.
    – Hot Licks
    Sep 2, 2022 at 20:57

1 Answer 1


The International Building Code (2006 IBC) requires foam plastic insulation to be separated from a building’s interior by an approved 1/2 inch drywall thermal/fire barrier or equivalent thermal barrier. which prevents the temperature from rising above 250°C Degree F (121°C) for a period of 15 minutes.

A thermal barrier is a material that is placed between plastic foams (including spray polyurethane foam) and interior spaces to slow the temperature rise of the foam in the event of a fire and to delay or prevent the rise of the foam. participate in a fire.

  • 1
    Yes, these various foam insulation formulations can either burn easily, or put out thick poisonous smoke, hence the protective barrier. This is also something to think about when using something like Reflectrix in an attic or garage roof.
    – Armand
    Sep 2, 2022 at 21:23
  • Interesting. The linked insulation is fiberglass, so not "foam plastic", but does it fall under the same IBC rule?
    – KJ7LNW
    Sep 2, 2022 at 22:11
  • @KJ7LNW that I do not know, sometimes they just put those warnings to protect them self, or to comply to code.
    – asinine
    Sep 2, 2022 at 22:23
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    @KJ7LNW -- the issue with the insulation you linked is the paper facing. I don't think any sort of fiberglass falls under the thermal barrier rule, but even if it did, avoiding it as simple as using unfaced fiberglass or mineral wool batts instead of the paper-faced batts you typically see Sep 3, 2022 at 2:08

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