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Community and Q&A

Window and Door Installations in “Thick” Walls

Rob Shuman | Posted in Energy Efficiency and Durability on

In reading various posts, I have noticed some innuendos and outright comments regarding the difficulties of installing windows and doors in framed walls with out-sulation and double stud walls. Being a novice at best, I would really love to hear opinions about the trials and tribulations involved. To structure the discussion a bit, please assume two wall designs.

Design 1: Drywall, 2×6 24” OC studs filled with R-23 MW batts, taped plywood sheathing (air barrier), 3” MW, WRB, furring, siding.

Design 2: Drywall, 2×4 16” OC studs filled with R15 MW batts, 2” gap filled with MW, 2×4 16” OC studs filled with R15 MW batts, taped plywood sheathing (air barrier), WRB, furring strips, siding. Outer (structural) wall and MW-filled gap between walls extend down to foundation/sill in front of the band joist to reduce thermal bridging.

I am leaning towards “outie” windows (hence the placement of the WRB in design 1 on the exterior of the MW out-sulation).

Although I am primarily interested in comments regarding the installation of windows and doors, I am always open to opinions about relative strengths and weaknesses of the two designs. With that in mind, I would plan on insulating the band joist from inside the basement as well (in both designs). The house is to be built in CZ 6 (inland 20-30 miles from midcoast Maine).

Thanks for your input.

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  1. Lucas Durand - 7A | | #1

    I'm sure you'll get a variety of responses.
    I prefer "outie" windows and doors primarily for "buildability" and because I prefer the appearance - both from the inside and the outside - even though there is some energy penalty to doing so.

    On my own house, which uses a sort of truss wall of 2x4 construction (14" thick from d.w. to WRB) I decided to go with "innie" doors to keep the depth of the wall consistent despite the in-swing of the doors.
    With hindsight, I'm not sure if I'd make the same decision again...
    I'd probably go "outie" all the way.

  2. Jin Kazama | | #2

    Rob : thermally speaking, there is a location within each wall design that will provide with the highest insulation efficiency, and it is usually close to the center of the insulation value.
    The difference might be of very limited impact.
    Then going for innie or mid wall placement provides with water protection on the window itself,
    and some degree of shading from high sun ( which then requires shorter overhangs/sunshades )

    Outie windows are easier to WB , but the comprimise is the complexity of vapor sealing on the interior ( requires extensive buck to wall to window sealing to minimize condensation possibility )

    Lucas: could you explain the " buildability " ?? i guess you are refering to the application of the WB
    being more in the same "plane" as the wall.

    I have installed both outie and innie windows in high performance walls
    ( notably ICF and REMOTE type walls )
    and it was a question of compromise , but the installation from inside on the innie version
    was much easier for the window itself, but required a complex water management setup.

    If the window/door is provided with sufficient overhand/sunshade as to provide protection from 80%+ of all rain , the water problem with innie becomes much less of an issue/concern.

  3. Lucas Durand - 7A | | #3

    "Buildability" - In my opinion you can't beat an "outie" for ease of completing a good installation because the exterior flashing is straight-forward and detailing the bucks for airtightness with some good tape on the interior is also straight-forward.

    But there is an energy penalty as a compromise.

  4. Dan Kolbert | | #4

    It's also, in my experience, cheaper to do outies. The labor and materials required to successfully weatherproof innies are substantial. And I agree w/ Lucas that they're a lot easier, esp. if the installer is inexperienced with the details.

  5. Expert Member
    Malcolm Taylor | | #5

    Outie doors pose a bit of a problem in the they can't swing past 90 degrees. In many configurations this isn't an issue and where it is a couple of common solutions are to bevel the opening or provide a thinner wall on the hinge side for a short distance - both of which unfortunately reduce the insulation around the opening.

  6. Rob Shuman | | #6

    Thanks for the comments.

    The focus of the comments seems to be on the "innie" vs "outie" issue as opposed to what I intended as the primary thrust of my question (relative difficulties of window/door installations in double stud walls and "outsulated" walls). However, I am not complaining, all of this information is helpful.

    Can I gather from this focus that one wall design or the other does not present special or unique challenges (just variations on a theme)? Is it safe to assume that the ability to effectively install windows or doors in either design should NOT be a factor in deciding upon a wall design strategy? Part of the reason for my asking is just a sense I have that windows or doors installed in a double-stud wall might tend to be more "robust" because they tie in directly with the frame of the house. That said, that "sense" may not be worth two cents...


  7. Expert Member
    Malcolm Taylor | | #7

    It's not a straightforward question because each type of wall has variants that greatly affect the complexity. A wall with four inches of XPS on the exterior is a lot different than an inch. Similarly double stud walls sometimes have fibreboard or no sheathing which creates difficulties.
    That aside, I think it is generally agreed that installing and flashing windows in a double stud wall is a lot easier than with outsilation.

  8. Dan Kolbert | | #8

    Outie install in a double-stud house is simple - the same as any standard install. Outie with foam is trickier; you need nailing, integration of drainage plane, etc, but still not that tricky.

    Innie with double stud is a pain - we've done it and it requires the inner and outer RO's to be sized differently, a lot of coordination of various tapes and wraps, and a lot of tricky nailing.

    Innie with foam is perhaps a little easier than outie with foam for install, but harder to integrate the drainage plane.

    In my humble opinion.

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