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Exterior insulation window detail example.

drewintoledo | Posted in Green Building Techniques on

Please help!   My build begins next week and I will be wrapping my house in 2.5″ exterior insulation held on with 1×4 furring strips.   I may finish with vinyl, James Hardie, or similar product.
I have 2×6 walls and my sheathing will act as the air & WRB.   I have flangeless triple pane windows, but I’m having difficulty understanding how to detail the exterior side of the window with the exterior insulation.   I was unable to find an architect in my area willing to design this detail for me.
I understand there are various methods, but I am really hoping that a few of you could attach some sample detail drawing snippets of some details for reference.

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  1. kbentley57 | | #1

    " I may finish with vinyl, James Hardie, or similar product."

    The choice of finish greatly dictates the advice given here. If it's vinyl, it should be installed against a flat surface, whereas the hardie or lp smartside can go on the furring strips. That has an effect on the window detail, along with the flashing. If you nail down which it is you're planning on using, you'll get more advice.

  2. drewintoledo | | #2

    Thanks Kyle. Plan is either James Hardie or LP smartside which I feel would have similar detail. I added vinyl because I am told a very thick vinyl is on the market that can be installed on furring, but wasn't 100% sure.

  3. kbentley57 | | #3

    There are quite a few different methods, but they all involve creating some kind of box for the window to set in, and all have window trim that turns perpendicular to the siding. Does your window manufacturer have a technical dept. that you can contact and describe the situation? I bet they've got a detail for most handy that they can send out.

    Here's a BSC article that has some info, you'll probably want to scroll down towards the bottom:

    A FHB article, albeit without the insulation:

    A Protradecraft vid:

    Just keep searching for those kind of things and you'll have it sorted out soon.

  4. user-6184358 | | #4

    Youtube - NS Builders They did window bucks for flangeless windows

  5. Jon_Lawrence | | #5


    I have triple pane flangeless with 3" exterior insulation and here's what we did:
    - The window frame is inline with the zip sheathing. Most of my windows have aluminum cladding and some are all wood, but in both cases the wood frame is inline.
    - With the window frame inline, it made it easy for me to tape the exterior. I used tape with the pre-cut back so you can easily line-up the right amount of tape for the window frame. I decided to tape first than insulate from the inside using sheep's wool. My tape supplier later told me he has a client that insulated from the outside with spray foam and before the foam cures completely, he goes back and presses any over expanded foam back flush with the frame to avoid having to go back and trim the cured foam. Saves time and then he tapes.
    - Another thing I learned halfway through the window install was it is easier to apply the inside tape to the window frame before installing the windows than to tape afterwards - see picture with white Contega tape.
    - Before installing the Roxul, my crew made window bucks out of Azek and attached directly to the window frame. This was slighter easier with cladded windows because the cladding held the buck in place. It just took 2 guys instead of 1 to install the bucks with the wood only windows.
    - The furring strips hold the buck in place and the we used 8/4 Azex for casing to cover the furring otherwise the 5/8" Artisan Hardie would have sit proud of the casing. Since we had to use 2x4 for furring due to the heavier Artisan requirements, we had to add an extra layer of 3/4" Azek behind the Coravent but you should be fine with the 1x4.

    Good luck!

  6. drewintoledo | | #6

    PLEASE keep the replies coming. This is FANTASTIC! Wow guys! You are lifesavers. I REALLY appreciate your feedback!! Whatever I choose my mind is at ease knowing I just need to create a window buck. Seems like everything will fall into place such that I have my buck depth correct. Just curious Johnathan, what are all the squares for on the lowest strip of siding in the middle photo?
    Hey Kyle, I reached out to the manufacturer months ago (Logic windows, which are rebranded Ventana) and I was somewhat disappointed they didn't quickly offer a solution or drawings.

    1. Jon_Lawrence | | #7

      Those are for electrical penetrations for the heat-pumps. The sleeves in the concrete are for the line-sets.

  7. drewintoledo | | #8

    Gorgeous! Do you recall what size sleeves you used for the minisplit line sets?
    Also curious if you have any photos of your electrical mounting plates before the wall layers were put on? Did you build up a wood block behind them?

  8. Jon_Lawrence | | #9

    The sleeves are 4", we were able to fit the line-sets for 2 outdoor units in a sleeve. For the electrical boxes, we made our penetration with a 1" PVC pipe that the wire sits in, then we attached nailers to the vertical furring strips that the Azek and electrical boxes are attached to. I don't have any pictures of that unfortunately.

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