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Is Icynene spray foam also a good air barrier?

sunstone | Posted in Energy Efficiency and Durability on

We are building a double 2X4 wall house (Walkout basement walls of ICF blocks, then 1 story above) and are contemplating using spray foam for 2X4 walls.

Large amount of foam. Can the foam be counted on as an air barrier, especially to seal the wiring on the inner wall?


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  1. sunstone | | #1

    OMG Just read through the thread on Spray Foam/ Installation.
    Now I don't know.
    Maybe we should be going the cellulose route.
    P.S. I'm really enjoying having my own thread

  2. davidmeiland | | #2

    Double walls? Cellulose!

  3. sunstone | | #3

    Yeah. Cellulose does look like the friendlier way to go. Does the insulating job. I don't fully understand a few possible aspects of it that have been mentioned at GBA.
    It has some level of resistance to air infiltration.
    It can deal w/ some moisture if it gets in.
    If using thick (12-14") walls where is best to put the air barrier i.s. or out
    Was looking forward to allowing the foam to be the air/moisture barrier, not sure now.
    P.S.--- Zone 6

  4. jklingel | | #4

    Richard: Look up ADA (airtight drywall approach). That is one option. A material called Membrain is another. A builder up here uses plywood, taped seams, as his air barrier. Go with cellulose. On the builditsolar site, look up Robert Riversong; he has good info there on applying the stuff. Remember to keep the exterior wall sheathing/etc, very vapor open, too. Foam will work, but it is kind of spendy.

  5. GBA Editor
    Martin Holladay | | #5

    Q. "Is Icynene spray foam also a good air barrier?"

    A. Yes, as long as (a) the installer is not sloppy, and (b) it is installed at a thickness of at least 3 inches.

  6. bxxKT22MVd | | #6

    short answer is yes, Icynene is a certified air barrier per ASTM e283. Cellulose is not it is that simple.
    The Icynene will be the air barrier while the cellulose is not, the plastic mesh holding it in place is. The foam house, everything else the same, will be tighter no question. That fact cannot even be argued.
    You have to find a reputable dealer that is experienced with your type of situation. Blower door test before drywall would verify results easy enough.
    ps. always include where you are.... kind of important. me, zone 5A, Massachusetts

  7. davidmeiland | | #7

    The Icynene will be the air barrier while the cellulose is not, the plastic mesh holding it in place is

    How would plastic mesh be an air barrier?

    If the OP chooses to use cellulose, he should detail his sheathing and his drywall as air barriers. I have inspected a couple of houses lately where SPF was used but there are still air leaks, such as under the mudsills, between ganged studs, etc. SPF only fills cavities.

  8. homedesign | | #8

    Spray foam at an adequate thickness may be an air barrier material..
    It does not guarantee an air barrier assembly or an air barrier enclosure.

    Spray foam is a very expensive option for an extra thick wall.

  9. GBA Editor
    Martin Holladay | | #9

    When cellulose is blown behind plastic mesh, it is always air-permeable mesh -- so you are mistaken if you think the plastic mesh is an air barrier.

    Dense-packed cellulose (installed at a density of 3.5 pounds per cubic foot or greater) greatly reduces air leakage, but it is not an air barrier. Cellulose-insulated walls can have an air barrier at the sheathing layer (for example, using Zip System sheathing) or at the drywall layer (using ADA).

  10. homedesign | | #10

    Stuart Fearn:
    The foam house, everything else the same, will be tighter no question.

    Stuart, I do not agree
    There are many examples of extremely "tight" homes being built without Spray Foam.

  11. GBA Editor
    Martin Holladay | | #11

    Researchers report that on average, homes insulated with spray foam have lower air leakage rates than homes insulated with cellulose or fiberglass. I reported on these findings in the April 2005 issue of Energy Design Update. You may remember that I have quoted from that article in the past.

    Of course, a conscientious builder of cellulose-insulated homes can exceed the average results.

  12. homedesign | | #12

    Most homes are not built with double stud walls either.
    I believe that an alternate(to sprayfoam) airtightness strategy will be more affordable in high performance walls and ceilings.

    spray foam might be a good choice for a not-so-conscientious builder

  13. sunstone | | #13

    If the dried cellulose is sawn/ trimmed , is that dust toxic?

  14. GBA Editor
    Martin Holladay | | #14

    No. It's just paper. (Although any dust can irritate the lungs, all you would need is a paper filter mask to filter the dust. How about that -- you use a paper mask to keep the little pieces of paper out of your lungs.)

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