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Community and Q&A

Building wrap: under the exterior foam, or over?

Steve Vigoren | Posted in Energy Efficiency and Durability on

I am building a one story, unvented crawl space, vented attic 1350sqf home in zone 7, Northern MN. Basically going REMOTE. My carpenter and I were looking at the REMOTE manual today, and we noticed Tyvek building wrap was put on the sheathing before the foam was installed. I will have 3 1/2 inches of foam, 2″ resting on top and even with the outside edge of my 2 1/2 inch ICF’s, (both in and out) and 1 1/2 on top of that extending down under the ground level. All 3 1/2″ of foam will extend up to the top of 16″ energy heel trusses with blown cellulose in the attic. I think I read somewhere that some/most builders think the house wrap should be at the window level; I will be having triple pane Marvin outies. I also put 2×6 joists on top of my walls for a wiring chamber, and started sheeting the top of those today. We hope to finish that and start the trusses tomorrow, so we have some time, but not a lot, to make the house wrap decision. Any comments would be appreciated.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Steve,
    You should read this article: Where Does the Housewrap Go?

  2. Steve Vigoren | | #2

    Thanks Martin, good article.

  3. Joe Suhrada | | #3

    I only used 2.5" foam but used Drainwrap under it. My windows are on the sheathing there where the Drainwrap make the weather resistant barrier. I did "innie windows" and basically have exterior "extension jambs." However, if it is in your budget and you have time, I see no reason why you cannot put a second house wrap layer over the foam.

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