Insulating Brick Exterior Walls
RetroFoam in brick mass wall—opinions, alternatives?
I have a 1921 craftsman style home that I’m working on in the 4A/5A zone (St. Louis area). The exterior construction is two-course brick with a 1” wythe cavity, from the foundation footer to the roof. I’m trying to decide the best course of action to insulate the exterior walls. I want to avoid sheathing over the exterior brick for preservation reasons.
I’ve been researching using RetroFoam to inject between the two courses. It should (according to the dealer, and if properly installed) provide a layer of R4-5 insulation around the whole wall envelope, as well as an air and moisture barrier. I would augment this with board insulation on the inside walls, to bring the value of the whole wall assembly to R12-15 or so. A vast majority of the info out there is either a decade old or from the company or dealers themselves, so I’m not sure if there’s any fresh information for or against this product.
Anyone have any experience with the product, or other methods to insulate and eliminate air leaks and thermal bridging in this kind of mass wall?
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Replies
I have a similar vintage/construction house in the area. Insulating the walls that way will have little benefit, and will add some amount of risk to the building's durability.
The cavity in double wythe construction isn't continuous, and any insulation pumped into the void(s) won't be, either. The voids in these walls types are how these walls handle moisture loading, any changes can have unintended consequences. Often this means that more damage occurs before you notice it.
A brick foundation is uncommon in the area; most of that era and earlier are limestone. Still, if you do not have moisture problems in the basement, or they are managed, consider spraying cc foam on the basement walls, tying into the plaster-on-brick as best you can. Plaster on brick is airtight (if the plaster is directly applied to the brick), and tie the attic ceiling into the plaster. An insulated basement and attic, with as much air leakage reduction as practical, can cut your heat loss in about half while remaining fairly low risk.
Thanks for the advice! I'll look into tying in new basement and attic insulation. I was equally surprised by the brick foundation, but I believe it stems from the basement being only half-buried.
How did you manage airflow around existing windows and door openings in the wall? One of the issues I'm fighting right now is figuring a way to stop air around the existing window frames without demolishing the entire window to make improvements. It likes to spill in between the brick/plaster and the frame on the inside, despite being sealed up on the outside. I'm guessing air is getting in the wythe elsewhere in the wall and finding the easiest way out.
Thanks!