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polyiso facing material

ddubx6 | Posted in General Questions on

hello, just got a load of johns mansville enrgy 3 polyiso, it is faced with a cardboard looking material, their website says it is a glass reinforced facer that provides rigidity and resistance to indentation and crushing and is compatible with BUR, modified bitumen and single ply membrane systems, my question is if i use this on an exterior wall will it be moisture/water resistant enough or do i have to cover it with housewrap or something? exterior wall assembly will be board and batten siding, 1/2″ strapping for rain screen gap, polyiso, taped zip. my wrb is the taped zip which is flashed to outie window and door bucks.  i also wanted to tape the seams, will anything stick to this facer, i like and use zip tape a lot, maybe with some sort of primer? has anyone used this stuff for walls? the rest of the house is foil faced which worked great but i couldnt find any with the price and availability i needed.

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  1. Expert Member
    Dana Dorsett | | #1

    With a rainscreen gap it wouldn't need another WRB between the polyiso and the siding.

    If the facers are clean most housewrap tapes would bond reasonably well to fiberglass type facers. Asphalt/bitumen paper facers may need something else.

  2. Expert Member
    Akos | | #2

    I've used this type of poyiso for walls. The facer easily absorbs liquid water and tends to bend the panel afterwards. I always put the WRB over the foam.

    If your sheathing is taped, there is not much benefit for taping your foam. Most tapes will stick well enough to the fiber facer but the facer is pretty weak and easy to rip the tape+facer off.

  3. ddubx6 | | #3

    thanks guys, but i now have conflicting info, i agree with Dana that it shouldn't need another WRB but if Akos' experience with this stuff shows moisture issues should i put a quick layer of taped house wrap under the strapping to be safe, once its covered i won't know whats going on with it, but i am also on a tight budget that has been blown out the water with current building material prices, so if it isn't needed.....thanks

  4. ddubx6 | | #4

    one more thought, there will be a lag between foam install and siding install, so rain is an issue too, will the housewrap protect it from rain?

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