Better understanding of structural brick retrofit
Hi everyone –
I posted the other week about some serious freezing issues we are encountering on our 3 wythe brick home that was remodeled with kraft face fiberglass batt in a 2×4 stud wall and interior gyp.
I’ve been reviewing a handful of Building Science Corp articles and posts within this forum but still have a few questions I don’t understand.
While understanding that the building science clearly points to a exterior solution (2×4 furring with continuous EPS/Mineral Wool + new cladding) as the best approach, we will encounter zoning side setback issues in Chicago and I am concerned about the builder (still under warranty) agreeing to this approach without litigation.
Trying to better understand the interior solutions, I too think that the builder will not re-gut back down to the brick so that the proper assembly could be installed.
Has anyone successfully put in ccSPF into an existing stud wall effectively? This would prevent us from extreme amounts of demo. With this approach, I am still concerned about air infiltration. The building science article says the following:
“The use of semi-permeable foam insulation in full contact (or adhered) to the back of the existing masonry is the most common successful strategy for interior insulation retrofits in North America with an excellent track record of success. This method also has the advantage of being one of the most practical to achieve under field conditions. The use of air and vapor-permeable semi-rigid board insulation (foam or mineral fiber) can be successful if excellent airtightness is achieved and convection is suppressed, and often requires a vapor-permeable fluid-applied air-water barrier on the interior masonry surface.” [https://www.buildingscience.com/documents/digests/bsd-114-interior-insulation-retrofits-of-load-bearing-masonry-walls-in-cold-climates]
What I am having a hard time understanding is BSC’s says the use of an air permeable foam works very well if excellent air tightness is achieved. Where exactly is the air tightness coming from in their recommended approach, because the article says to spray directly on the inside face of the brick? I know in other articles it references a fluid-applied air barrier on the inside of the brick prior to spraying, but this one does not mention it.
Any other thoughts and considerations are warranted!!
Thanks!
-Scott
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Replies
quick update:
I've engaged a technical consultant from the Masonry Advisory Council to come out and assess the status/quality of our brick.
I'm curious to get their take on it's condition, as it could help us lean towards an exterior solution argument (the spalling is rampant from both the exterior and interior)
Your frozen brick can come from two sources, either moisture from interior air leaks or bulk water leaks into the brick cavity. You need to identify the source before it can be fixed. A brick expert is definitely a good start.
Air barrier referred to in most cases is the interior drywall. This needs to be detailed well to function as such, items like caulking around the perimeter and air tight electrical boxes are a must. Older homes also have a lot of 3d air leak paths which could end up dumping warm humid interior air into your wall cavity, these need to be dealt with. It is very easy to mess these details up.
The reason SPF retrofit generally works better is that it plugs all these air leak paths.
I'm in the land of century old double brick houses (zone 5) and SPF in the wall cavities is pretty common approach for insulating them. Provided water management details are good and the bricks are solid it generally works well. There is a period in late 1890s here where bricks were extremely soft, these don't tend to hold up well and best left uninsulated or with minimal insulation only.