Brick Veneer Insulation Retrofit Assembly Check
Hi all, I was hoping that someone could double-check my details on a proposed insulation retrofit of a brick veneer wall on my 1955 ranch-style house. I think I’m understanding the complexities of the assembly and responding appropriately, but vapor drive is one of the fuzziest of all the BS concepts to me.
A few climate considerations: I’m in Boise (CZ5), but only 5800 HDD, so on the warmer side of CZ5. Also, it is relatively dry here with only 13.8 inches of rain per year, with most of that coming in the cold months. April through early June are the only real crossover wet/warm months where we get about 1.3 inches of rain and have any temperatures above 65 degrees. Additionally, the wall faces East, and our temps in those few months don’t really peak until the afternoon, so the sun rarely beats on that side of the house when it is wet.
There are attached detailed drawings of the current situation, along with the proposed solution, but one thing that I sticks out to me is the double-layer of 6-mil poly behind the roofing paper and how that complicates a solution. My thinking is that the poly will stop vapor drive from the exterior, but also largely limit/completely stop any sort of drying potential to the exterior as well. In order to accommodate that lack of drying to the exterior, I need to respond by preventing interior moisture from making it to the exterior wall in the cold months as well as accommodate as much drying to the interior as possible. Am I thinking about this correctly?
I’m sure there are many solutions (assuming I’m understanding the concepts correctly), but my proposed is to remove the interior drywall and replace the R13 fiberglass with either Rockwool Comfortbatts or dense-packed cellulose, and then follow that with Siga Majrex as the air barrier/smart vapor retarder. While I have the wall open, it seems to make sense to use a Bonfig assembly to give the cavities more depth and a thermal break. Does that make sense as an approach to this situation? Or, is the Majrex SVR overkill so long as I properly detail the interior drywall as my air barrier?
I’ve read several articles on masonry retrofits, but most are relative to mass walls and not veneers. The closest I could find to my particular situation was an article written by Kohta Ueno (link below), but it only briefly touches on something related in Figure 5. Perhaps I’m overthinking things relative to the exterior poly, but would love to know if I’m off in my assumptions about my particular assembly.
Thanks in advance for taking a look.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part