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Community and Q&A

Outie 2x picture frame – some questions

GregDeitrick | Posted in Green Building Techniques on

Working my way through the advice in  “Installing Windows In a Foam-Sheathed Wall”,, at Step 1 I think I want outie windows, and at Step 2 I think I want housewrap on the exterior side of the insulation.  So far so good.

At Step 3 I think I want to go with the 5th option- a picture frame of 2x lumber because to my eye it looks to make air sealing easier.  My air control barrier is to be the exterior face of the sheathing.  After sealing the seams in the sheathing, membrane (peal-and-stick or liquid applied) would bring the seal to the “inside” surfaces of the rough opening (the sides facing the window assembly).  The picture frame would be installed, and the air seal extended with membrane to the “inside” surfaces of its rough opening.  And if I were to take the belt-and-suspenders approach and also form an air seal with the interior drywall, that would also be sealed to the rough opening.

Is that likely to work well?  Or is there an easier way?

In my case the picture frame will need to extend the rough opening out something like 4-1/2 inches.  Would it work to drill 2-1/2″ deep (for example) countersinks and consequently 2-1/2″ shorter screws for attaching the picture frame to the wall studs (so maybe 5″ screws rather than 7-1/2″ screws)?  What screw type, size and spacing would be appropriate?  I’m planning on a 4 ft x 4 ft or 4 ft x 3 ft window with a nailing flange.

Thanks for your thoughts.

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  1. GBA Editor
    Martin Holladay | | #1

    Concerning air sealing: There is no single answer to your question. The good news is that wall assemblies with 4.5 inches of continuous exterior rigid foam -- it sounds like that's what you are planning -- tend to be relatively airtight, due to the multiple layers with staggered seams.

    That said, it's always a good idea to detail penetrations (including windows) carefully to avoid air leaks. You tell us that you are using some type of "membrane" as your air barrier (on the exterior side of your sheathing). That's certainly possible, but it may be unnecessary. Many builders simply tape the sheathing seams, or tape the rigid foam seams, to reduce air leakage.

    Regardless of how you detail your exterior air barrier, you need to seal the seam between your window rough opening and your window frame to prevent air leaks. The two main choices are canned spray foam or a European tape (usually on the interior side).

    To attach your picture frame, you can countersink your screws if you want, or you can use long screws without countersinking. (You'll still need to predrill the holes, of course.)

    Some suppliers of long screws include:
    -- Best Materials — Dekfast 6-inch roofing screws and Dekfast 9-inch roofing screws>
    -- Wind-Lock (a source of long screws and plastic hold-down buttons)
    -- FastenMaster (a source of screws up to 18 inches long)
    -- GRK Fasteners (a source of screws up to 12 inches long).

    As far as screw spacing is concerned, I've always gone with common sense rather than engineering for something like this. I'm guessing that if you install screws every 12 inches, everything will be fine.

  2. GregDeitrick | | #2


    Thanks for the information. That answers my questions.

    I happen to be planning for Roxul insulation on the exterior due to wildfire risk. I have seen you remark elsewhere that with Roxul it is easier to detail Innies; it isn't clear to me why that would be the case if the Roxul is covered with housewrap for the water barrier as I intend to do. Putting the drainage plane between the insulation and the air gap behind the cladding seems so sensible to me that I have a hard time seriously considering other options. I do need to think through the details of integrating the housewrap with the window flange while simultaneously integrating the siding and trim with the exterior face of the window frame. I'll browse the detail library for that.

    For clarification: I plan to seal every wood-to-wood seam in the air barrier with one sort of membrane or another: tape, peal-and-stick, or liquid applied. But I'm not covering the exterior face of my plywood sheathing. The statement, "my air control barrier is to be the exterior surface of the exterior sheathing", reminds me that after taping the sheathing seems on the exterior side I still have to seal the edge of any seam that terminates at a penetration of the air barrier through the sheathing.

    Upon further reflection I can see now that air sealing plywood window bucks would be no more difficult.

  3. rockies63 | | #3

    What climate are you in? I am doing something similar to you in that I will be applying Roxul Comfortboards to the exterior sheathing but they are only 1 1/2" thick (In BC Canada I will be in zone 6 and a recent publication by the government says my exterior wall needs to be R22 to pass code and that much exterior insulation is all that's required).

    I was considering using 2x2 material for the exterior picture frame but then I found these insulated bucks.

    Finally, I am going to use Stogard Gold Coat on the sheathing for the exterior barrier.

    1. GregDeitrick | | #4


      I am in western Montana, zone 6 also. I have been notionally thinking 3" of exterior insulation but I have not looked into it carefully and made a final decision. I decided to make the building as wildfire resistant as practical because, among other things, the site would be relatively unsafe for firefighters during a major wildfire. Consequently I decided to avoid any kind of exterior foam insulation above grade, so the thermal bucks are out.

      I really like the idea of housewrap over the exterior insulation. I don't think additional water barriers are needed; compared to Houston, where I lived until recently, rainstorms here are fairly mild.

  4. Expert Member
    Peter Yost | | #5

    Hi Greg -

    In western Montana--a climate with less than 20 inches of precipitation annually, it's ok to install windows and doors with a "face-sealed" system (relying primarily on sealant at the face of the building to keep water out). However, in all other climates, drained-opening installation systems are needed to get the water out at the level of the WRB and flashings, draining the window installation in a plane NOT at the face of the building.

    From what I can tell from the ThermalBuck installation video (, this is a face-sealed installation system, particularly with no drainage at the sill of the installation. I would not use any window or door installation system that is not designed to drain in anything except a dry climate.


    1. BRINC_BP | | #8

      Thanks for the mention of ThermalBuck - we had to jump into the conversation. As Peter recommended, window face sealing is not the right answer for most of the US climate, but ThermalBuck can be face sealed in the proper application. We do not recommend sealing the sill of the window in most climates. ThermalBuck has a 2° slope built into all lengths for positive drainage. The slope is 1 3/4" long and drops 1/16", and sits under the window only. ( We do recommend planning the air and water seal where the interior of the window meets ThermalBuck. ThermalBuck has a waterproof coating, which creates an air & water tight seal around the entire rough opening, not just the sill and partway up the jamb. We also recommend installation with high-quality window and door sealants like DAP 800 Dynaflex. If you prefer more of a slope you could add a pre-made sill pan on top of ThermalBuck.

      These are all very important details and part of getting a high quality window install. The main reason we developed ThermalBuck, was to stop the thermal bridging that occurs at the mounting point of your window. Moisture moves from hot to cold and this thermal bridge leads to condensation in your wall cavity. View ThermalBuck's thermal performance test results at ( We welcome inquiries, and feedback.

  5. rockies63 | | #6

    I've read that for "outie" windows the housewrap should be installed over the exterior rigid foam insulation but can you do that for mineral wool exterior insulation panels?

    Peter: if you use the Thermalbuck product wouldn't you wrap the exterior air and moisture barrier around and over the Thermalbuck and into the window opening (turning it into one solid unit)? I'm thinking particularly of the Stogard Gold Coat liquid applied barrier system - taping the connection between the edge of the Thermalbuck and the wall sheathing and then coating the whole thing in Gold Coat. Wouldn't that be the same as using a 2x2 wood picture frame on the exterior and then sealing it and installing the window?

    1. GregDeitrick | | #7

      I don't see why one couldn't put housewrap over Roxul.

    2. BRINC_BP | | #9

      Scott- we thought we'd chime in here too, with our recommendations for integrating the WRB. We do not recommend wrapping the WRB into the opening, as this can cause leaks and make air sealing more difficult. If the WRB is against the wall, we recommend it going between the ThermalBuck and the wall only at the sill so you can get a good shingled effect. Please see our installation instructions (

  6. brendanalbano | | #10

    Why do you want outies and housewrap on the exterior of your mineral wool?

    With mineral wool, innies and housewrap between the sheathing and the mineral wool seems much simpler unless you have a really strong reason not to go that route.

    Here's an example:

    (The example uses Zip, but plywood/osb and a WRB would work well too).

    I ask because you said "I think" so perhaps are not fully committed to the outies, and it might be worth considering innies.

    1. GregDeitrick | | #11


      I read (a few times) Martin Holladay's post, "Where does the housewrap go":
      His recommendation, for exterior foam board insulation, is that both innies and outies work just fine provided the water control barrier is nominally in the same plane as the window frame. To a first approximation the analysis is not changed at all, IMHO, if mineral wool board replaces the foam board. If anything I would expect the mineral wool to have at least somewhat higher permeability to water and air. So increasing exposure of the mineral wool insulation to water and air by putting it over the housewrap certainly isn't going to improve the insulation's performance or durability. So if anything this favors putting housewrap over the mineral wool insulation. This difference may be insignificant, and innies may work just fine, but substituting mineral wool for foam board does not increase the advantages of innies.

      Martin mentions a few "innies are better" and "outies are better" arguments which obviously didn't convince him of a clear "best" choice. The report, "REMOTE A Manual", Cold Climate Housing Research Council (2009, revised 2013) mentions a few cons of outies, "based on anecdotal evidence in 2x6 walls using six inches of foam board during negative forty degree cold spells in Fairbanks, Alaska." One is, "where the jamb passes through the sheathing presents a weak spot for water infiltration. I am not a building professional so you could easily convince me that one can achieve a much more robust water barrier at the face of the sheathing than with housewrap over the insulation. And if my building was exposed to severe wind-driven rain storms I might believe that to be an important consideration. But that is not at all common in western Montana as far as I can tell. The second con that they mention is that outies appear more prone to interior condensation and frosting. My building is a workshop with 6 modest-sized windows primarily for summer ventilation. During winter I only care about staying warm and minimize propane costs so I may well cover them with foam board from the inside.

      1. brendanalbano | | #12

        My thought is that:

        Both approaches are viable: innies vs outies, WRB behind or in front of the insulation.

        You are concerned about how to detail the "picture frames" with the outies.

        Switching to innies and WRB behind the insulation seems like it would eliminate the detail that you are concerned about.

        Just food for thought!

        Sidebar: The reason I think mineral wool is a good candidate to having the WRB be behind it is for the same reason that you are worried about the WRB being behind it: because it's permeable! Putting your WRB behind rigid foam always felt a little odd to me (unless you use hydrogap or something) because your "drainage plane" can't really drain since it's sandwiched tight against the foam. That said, plenty of folks don't think this is a problem. Regardless, with the mineral wool, your drainage plane can easily dry to the outside through the mineral wool. And my understanding is that the mineral wool is hydrophobic enough that it won't get saturated behind your rainscreen, so there's no issue with it being exposed to some water. The Zip sheathing + mineral wool system seems to be endorsed by Building Science Corporation and other highly respected folks, so that alleviates any concerns I might have about having the WRB behind the mineral wool. Finally, conceptually, your water control layer is more important than your thermal control layer, so having your insulation protect your WRB feels right to me, as opposed to doing it the other way around. But that's a whole lot of gut feelings, and both approaches definitely can work :)

        1. GregDeitrick | | #13

          My concern about detailing the picture frame was that I wanted the housewrap in the plane of the back side of the furring strips for the cladding and the window flange in the plane of the front side of the furring strips. I thought this would be a common situation but the "window flashing howto" videos I had seen up to that point had the window flanges in the same plane as the housewrap. Since then I have seen details which use metal Z flashing above the window that laps under the housewrap and over the window flange. That seems to be the standard solution for my situation.

  7. rockies63 | | #14

    Mr. Brooks, thank you for the links for the Thermalbuck system. I can see that the Thermalbuck is being installed directly on top of the OSB sheathing but I have a question about what to do about the WRB. Please have a look at this video on the Stoguard Gold Coat product I am considering.

    As you can see, they have detailed instructions on how to finish off the window and door rough openings. However, with your product this process doesn't seem to be needed. In fact, you say that wrapping the WRB into the opening can cause leaks and make air sealing more difficult.

    If I install your product around the window and door openings would you suggest applying the Gold Coat to the sheathing so that it just touches the edge of the Thermalbuck or should I use some of the Gold Coat mesh to lap up the outer side of the Thermallbuck (maybe just a bit) and create a seal?

    1. BRINC_BP | | #15

      Mr. Wilson, first of all thank you for considering ThermalBuck in your build. I did watch the video you attached and the system looks very interesting. I am leery of recommending the two systems together without any testing though. Do you have a contact at Sto I can reach out to discuss some testing of the two products together? I am surprised I have not run into this system yet. We have tested with several systems and the bonds test out just fine but I like to err on the side of caution, we want your home to perform well. As long as there is good adhesion of the two products I think it would make sense to run the mesh on the face of the wall and up the 90° angle of ThermalBuck, then place the fill coat over the mesh. If I am understanding the system correctly then the final coat would need to be applied over the fill coat to make it water and air tight. I would still use the DAP 3.0 behind the ThermalBuck and in the mitered corners. The DAP 3.0 makes an incredible air and water seal that has been thoroughly tested.

  8. rockies63 | | #16

    Mr. Brooks, Bob Tayson is the LEED Green Associate at Stocorp.

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