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Community and Q&A

Flashing Windows in Walls With Exterior Foam Insulation

AndersB | Posted in Green Building Techniques on

I’m planing to install windows in a wall made up of 2×6 with dense packed cellulose, OSB, house wrap, 3″ EPS, rain screen, siding.
My intention is of install a 1×3 picture frame flush with the insulation (and screwed into the studs) with 2″ foam between the frame and the sheeting. My dilemma is how the flashing should be executed aroun the window and the opening in the housewrap. I have seen this type of install now and then in FH but no details on the flashing. One alternative is to move the housewrap to the outside of the EPS when conventional flashing could be used.
Suggestions please….

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  1. user-2310254 | | #1
  2. wranch | | #2


    This is identical to my chosen wall assembly for my remodel, minus the trim details. Your windows and other penetrations should all be flashed to your water barrier. If you put the housewrap or water barrier layer on the OSB, that becomes the plane that everything is flashed to keep water out. This is also considered "innie" windows. With the housewrap outside the EPS they would be "outie" windows.

    Lookup the installation details for the housewrap(s) you are considering or have already chosen. They will have details for proper flashing.

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