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Is there a compatibility issue with Zip (Huber) R- Sheathing and open-cell Icynene?

While constructing a home in Eastern MA and utilizing 11/2" Zip R Sheathing on 2x6 walls, Icynene Open Cell foam was sprayed into the stud bay/wall cavity (against the Foam board backing). Shortly after spraying I checked a few spots to see the consistency of the foam and noticed that the foam had not adhered to the Zip foam board, creating a gap ranging in size from 1/4" to 2". There were a few locations where the foam had adhered, but the majority of the test spots revealed a gap as noted.
Has anyone had any similar experience with this apparent compatibility issue? If so, what was done to remediate the problem?

If the gaps are left and not filled with insulation, will this be a potential problem area for condensation?

The foam installer, Huber and Icynene have all been notified (and have reviewed on site), but have no explanation or solution at the time of this posting.

Any feedback or suggestions would be appreciated.

Asked by Jonathan Hahn
Posted May 2, 2014 4:26 AM ET
Edited May 2, 2014 5:53 AM ET


6 Answers

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I'm guessing that there was a problem with the spray foam installation. Problems with unexpected gaps in spray foam are well-known, and are usually attributed to installer error (bad mix of components A and B, installation under unfavorable temperature conditions, etc.).

Answered by Martin Holladay
Posted May 2, 2014 6:32 AM ET


Jonathon. You should not have done the spray foam. It has no benefit.

If you wanted higher R there are much more correct ways to assemble.

Open cell is notorious for not sticking well in layers. The experienced crews know this.

I am guessing that the gaps in a wall would not be a problem but if that happened in an unvented cathedral ceiling it would have to be repaired.

So... I think your situation is not a problem.

Are you filling the whole wall with spray foam? What kind? Explain your whole wall assembly.

Answered by aj builder, Upstate NY Zone 6a
Posted May 2, 2014 7:01 AM ET


Martin I do not think your post is correct. Spray foam open cell anyway has issues sticking to some items and Zip R may be one item. It has issues sticking to itself even.

Answered by aj builder, Upstate NY Zone 6a
Posted May 2, 2014 7:04 AM ET


Martin, In your opinion is the gap between the foam board and spray foam a concern as a condensation point since the foam board and OSB in the Zip system are only R 6.6?

The wall assembly as noted above is 2X6 frame sheathed with 1.5" Zip R- Sheathing (R6.6)http://www.huberwood.com/zipsystem/products/zip-system-rsheathing . (The Zip R Sheathing has a glass- mat facer to which the open cell foam has been sprayed). The wall cavity is filled with open cell foam (R-20.3) in its entirety. The spray foam was not sprayed in layers, the foam mix was noted as correct by both Icynene and the installer based on the surrounding areas and its ability to stick to all the other substrates it encountered, including plywood and framing lumber. The cellular structure of the spray foam was also noted as consistent and proper for the application.

Answered by Jonathan Hahn
Posted May 2, 2014 9:06 AM ET


I don't think you'll get condensation on the interior side of your R-sheathing. But these voids aren't good, for several reasons -- including the obvious one, that you aren't getting the R-value you expected, because the void is just air.

Depending on the size and number of voids, your spray foam installer should propose a fix that satisfies your expectation that the insulation be installed without any voids.

Answered by Martin Holladay
Posted May 2, 2014 10:05 AM ET


Martin, this project sounds like the homeowner was part of asking for this experiment. I say leave all alone and all will be fine. the air spaces will insulate too as the wall now is quite airtight compared to a wall with fiberglass and still is very highly insulated mistake or not.

Jonathon. Your home is way more energy efficient than homes of the past. I bet you will be very happy with the performance.

You will need to know how tight your home is, ACH and you will need to deal with air exchange in some manner to handle your indoor air quality issues IAQ. And you need to not make more mistakes in the rest of you build. Priorities.

Answered by aj builder, Upstate NY Zone 6a
Posted May 3, 2014 7:19 AM ET

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