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Community and Q&A

Wall Assembly Climate Zone 3

PatriciaCranberry | Posted in Green Building Techniques on

Ready to finalize my wall assembly. I’m just not sure about this House Wrap layer. Would it be best where I have it now (see below) or have it between the XPS rigid foam and the slicker drainage mat?
1/2 inch gypsum
2×6 wood framing
Cavity insulation with blown-in cellulose (R-20)
1/2 inch OSB structural sheathing
House Wrap (as Air Barrier)
1 inch Rigid XPS Foam (R-5) (mainly to reduce thermal bridging)
Slicker drainage mat
LP Smart side panels and trim with insect screen and appropriate flashings.

I’ll keep studying the site…Thanks in advance

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  1. GBA Editor
    Martin Holladay | | #1

    You might want to start by reading this article: Where Does the Housewrap Go?

  2. user-2310254 | | #2

    Inger. It depends on whether you are installing innie or outie windows. See this article for more information.

    You also might want to tape the seams on the OSB and rigid foam.

  3. PatriciaCranberry | | #3

    Thanks Martin/Steve: I really want the house wrap next to the OSB (innie window style) but I think outie windows would be my 1st choice--so that means OSB/Rigid Foam/House Wrap.... I know in my climate zone 3 it is zero thickness required for protecting the sheathing from moisture....and I understand the differences between polyiso (old and in the cold), EPS and XPS. Makes me nervous....but if the OSB were to get wet, it would dry to the inside right? No vinyl wall papers.

    Given that my wall assembly with 5.5 inches of cellulose should meet the 2012 IRC (and I'm in a permit free area- no county or local jurisdiction and the nearest municipality is still using 2009 IRC). I'm really only using the continuous insulation to prevent thermal bridging, although the extra R value is an added benefit.

    What would you recommend for use as continuous insulation in Climate Zone 3 with a 6" stud wall filled with cellulose? Is there a minimum amount of material/thickness that accomplishes the thermal break? I know I'm paying the bill (both for construction and future energy costss) but I also want my builder to not have to use special fasteners for those thicker wall assemblies. Thoughts?

  4. GBA Editor
    Martin Holladay | | #4

    Q. "What would you recommend for use as continuous insulation in Climate Zone 3 with a 6-inch stud wall filled with cellulose?"

    A. Any type of rigid foam will work. EPS and polyiso are more environmentally friendly than XPS. If you can buy recycled (reclaimed) rigid foam, that's the greenest (and cheapest) route to take. For more information on this issue, see Choosing Rigid Foam.

    Q. "Is there a minimum amount of material/thickness that accomplishes the thermal break?"

    A. No. Thicker rigid foam insulates better than thinner insulation, of course, but the energy savings per inch diminish as the foam gets thicker. In your climate zone, 1 inch of rigid foam sounds about right.

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