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

Continuous insulation with non-integrated WRB window flashing (moistop method b)

sazerac | Posted in General Questions on


My window installer installed my windows using an older method seen here:  The windows were installed without any housewrap on the sheathing and don’t have flashings that are integrated into a WRB (there’s currently no WRB installed), nor do they have a sill pan. Is there any way I can incorporate continuous rigid insulation with the windows being innies and using foil faced and taped polyiso as the AB/WRB? Or is this a situation where the windows either need to be pulled and flashed so that they’re integrated into a WRB or I scrap the idea and leave out the polyiso?

I live in climate zone 3B (San Diego, CA). I have fiberglass Marvin Integrity (Essential) windows. The siding will be stucco. I normally wouldn’t have bothered with continuous insulation but it’s a south facing wall and the thermal bridging is really noticeable. 


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
    Brian Pontolilo | | #1

    Hi user-7700619.

    Too bad they didn't put some flashing tape inside the RO and set your windows on a pitched sill and/or include a back dam, but if the windows were installed as shown in that video including the WRB, I think you would be fine to install exterior rigid foam and if your sheathing wasn't detailed as an air barrier, the foam with some sealant here and there and taped seams will help with air sealing.

    If you choose not to go with the rigid foam, it's a good idea to have an air space between the stucco and the sheathing. Some builders use a second layer of WRB, but better some type of 3D drainage mat, like these Rainscreen Products for Stucco Installations.

  2. sazerac | | #2

    Hi Brian,

    Thanks for the reply. I think a lot of installers in San Diego skip the sill pan flashing because we don't see much rain and it's usually warm. Of course that doesn't account for sprinklers hitting windows, etc. I've used closed-cell foam to air seal any penetrations for plumbing and electrical and I'm planning on using a fluid applied flashing to seal the seams in the sheathing as well as the bottom edge.

    Based on your feedback my plan is:
    * Apply fluid applied flashing to sill plate/sheathing connection
    * Apply fluid applied flashing to sheathing seams
    * Install WRB (I think the stucoo installer does a double layer of 60 min paper)
    * Install 2" polyiso with taped seams
    * Install 1x4 strips to attach lath
    * Install lath with rain screen backing as you mentioned

    Thanks again,

    Edit: Type sill plan/sheathing connection -> sill plate/ sheathing connection

  3. Expert Member
    Akos | | #3

    Take a look at the link I posted in this thread, the link in it shows stucco details with exterior insulation:

    Grooved foam is stock item at most EIFS suppliers, it avoids you needing rain screen backing or the 1x4 strips.

    2" of exterior rigid insulation is a lot in your warmer climate, you'll probably get most your energy savings benefit with 1" of foam.

    There is no need for two layers of WRB under the foam, the two layers are only needed if the stucco is directly applied.

    1. sazerac | | #4

      Hi Akos,

      That's for the detail link. It looks like the stack up is:

      * Sheathing
      * WRB
      * Foam (hopefully I can find grooved)
      * Paper
      * Lath

      Is my understanding correct? I just want to make sure my stucco guy does it right. It's a bit uncommon in San Diego to do exterior continuous insulation on most residential projects. Also worth noting, my cavity insulation is mineral wool with no vapor barrier.

  4. jollygreenshortguy | | #5

    I definitely would NOT use this window installation solution anywhere in the USA, even San Diego. There must be a sill and back dam with no caulk at the window's bottom flange.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |