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Community and Q&A

Is black fiberboard the same as “iso”?

jcog | Posted in Energy Efficiency and Durability on

Here is the response I got from a roofing company when I asked why they were using black fiber board instead of ISO board on a flat roof installation at my house which was stipulated on the proposal I signed.

Can anyone confirm if this is true or not, because it doesn’t make sense from what I have learned over the years and maybe I have missed something about what iso means exactly … as I thought it was a poly-based material.

“They are using iso it’s a black fiber board, it’s what we use on all flat roofs.”

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  1. Expert Member
    Akos | | #1

    Sometimes the facer on the polyiso is black in color. Asphalt coated wood fiberboard, which is also black, is also used a fair bit on flat roofs but it is only R2.5/inch vs R5.7/inch for polyiso. If your roof R value is important, I would make sure they are putting the correct product on.

  2. Expert Member
    BILL WICHERS | | #2

    I don't like referring to the material as "iso", since that seems to cause confusion. The full name is "polyisocyanurate", but most just call it "polyiso". It's important to stick with convention when referring to materials so that everyone stays on the same page.

    There are three common forms of polyiso by appearance. You're probably most used to the "foil faced" polyiso that looks silver, and is the type commonly stocked at the box stores. There are also "fiber faced" versions, with the most common two being a brownish kraft paper facer, and the other a black fiberglass mat. Both of the fiber faced types are commonly called "roofing polyiso", and they are commonly used on commercial flat roofs.

    My guess is your roofers are using the black fiberglass mat faced polyiso, which is fine. Check by looking at the edge: the edge should be a yellowish/whiteish color, and it should look like the edge of a foil faced polyiso panel. You should be able to dent the foam on the edge with your finger if you poke it. It's possible that "black fiberboard" is asphaltic fiberboard, which is NOT a thermal insulation material. I doubt roofers would be using asphaltic fiberboard as insulation, so you're most likely seeing the black fiberglass mat faced polyiso going down.


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