GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Structural design for insulating around a window wall

Gabriel Solomon | Posted in Green Building Techniques on

Dear all, 


I’m planning an addition in climate zone 5. The east wall will be more than 50% glass, and I’m wondering how to structurally implement this with exterior rigid foam insulation. The building will have 4” EPS in a single vertical plane on the exterior of both the framed walls and the foundation walls.


I don’t think its practical to float that much glass in an “outie” configuration the way I will be doing with the rest of the windows and doors in the project. The problem in this case is really how to insulate the surrounding framed and foundation walls.


If I place the window wall directly on the foundation, structurally that would be ok, but then the rigid insulation on the crawlspace concrete wall below the windows would protrude. The crawlspace will be sealed and conditioned, so I really don’t want it to be a cold wall. Could I just put the rigid foam on the interior of the crawlspace wall?


Any suggestions would be appreciated. Thank you.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. GBA Editor
    Peter Yost | | #1

    Hi Gabriel -

    I am having a hard time nailing down just what your assembly(ies) look like. You may need to provide details or hand-drawings. It's a confusing picture you paint for me with discussion of windows, walls, and the crawlspace.


    1. Deleted | | #3


    2. Gabriel Solomon | | #4

      Hi Peter, For some reason this site is not showing my drawings - I'll try uploading again later a drawing of what the wall assembly will look like. In the meantime, as I described, the windows and doors will be "outie" and protrude from the base sheathing by 4.75". For most of the project, that's fine.

      My problem is for only one wall of the house, where the vast majority (~90%) of a 342 sq. ft. wall will be glass, it doesn't seem practical or feasible to overhang the framing 4.75" beyond the stem wall. Therefore, I can't add rigid insulation to the exterior of that stem wall without it sticking out from under the windows like a strange sort of goatee.

      Therefore, can I effectively install rigid insulation on the inside of the crawlspace wall beneath (only) the window wall without adversely affecting my crawlspace envelope?

      Thank you, Gabriel

  2. Expert Member
    Akos | | #2


    I've seen a larger popped out windows supported with LVL bucks. Not cheap but definitely sturdy.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |