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Community and Q&A

Window installation with external foam

Jaccen| Posted inGeneral Questionson

Hello all.

Thanks, up front, for any and all input.

Background:
-SW Ontario (Zone 5/6 border so we’ll go with 6)
-2 storey house (approx. 2500sqft total, even split per floor)

-standard 2″X6″, 16″ OC frame construction
-taped 1/2″ plywood sheathing
-outie windows

I’ve created the following window installation plans and would appreciate any feedback/critique on them. Located here or attached:

https://drive.google.com/open?id=12YQtOx_bPAX9-n3SSgroFmSHdQeCvmsI

It’s heavily based on the Mass Save Deep Energy Retrofit Builder Guide and the following articles:

https://www.buildingscience.com/documents/insights/bsi-085-windows-can-be-a-pain

Installing Windows In a Foam-Sheathed Wall

Where Does the Housewrap Go?

Window Installation Tips for a Deep Energy Retrofit

Basically, I’m wondering about the housewrap. Per the articles, it seems it would be best to integrate the water barrier into the window (thus, on the outside of the foam).

I was just wondering if that’s still the recommended construction method.

Thanks again,

Jason

File format

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Replies

  1. GBA Editor
    Peter Yost||#1

    HI Jaccen -

    For your climate (more than 20 inches of precipitation annually), best practice is a drained opening installation. That means that the rough opening is flashed and weatherlapped with the WRB and then the window installation is also flashed and weatherlapped in a separate sequence.

    In your drawings, these issues/items come up:

    1. your rough opening sill flashing should be back-dammed or sloped or both.

    2. your window install should be done is such a way that the rough opening sill flashing can drain unimpeded down and out of your window opening.

    3. exactly how to install and weatherlap of the metal window cap is to me still a matter of debate. I like to have the cap go behind at least the furring strips, with a high performance acrylic PSA tape counterflash.

    Peter

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