Best way to insulate interior of existing above-grade block wall in SE PA?
I am renovating my southeastern PA house that was built in the 50s. The entire structure is concrete block wall with stone and stucco exterior. On the interior, there are 3/4″ wood furring strips and plaster walls. The house will continue to have hot water baseboard heat, and I will be adding ductwork and whole house air conditioning.
Regarding the wall assembly, what are my best options for insulating the interior without eating too far into my already limited living space? I’d like to add at most 2×4 framing against the block walls, but I am concerned with how vapor drive from the interior or exterior (depending on the season of cousre) will affect my insulation choice.
Is closed cell foam my only option without jumping to 2×6 framing? Should I be considering some sort of rigid foam (like XPS) as part of the solution? The bottom line is this: how can I tighten up the wall assembly, achieve required R values, and avoid moisture problems while limiting myself to a 2×4 interior wall?
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Replies
Tim,
How would you feel about adding rigid insulation to the exterior and/or interior? What is your plan for the roof?
Thank you for your questions and consideration. Rigid insulation on the interior is an option. However, as far as I am aware, I will need 3-4" of based on available products and their nominal r-values (2" of XPS is ~r10 in a proper assembly) - which means I need a creative solution for wiring and outlets on exterior walls. Interior insulation on the walls is the problem I am looking to solve. Asking about the rest of the overall housing assembly is understandable; I should have mentioned that the floor of the attic (plastered ceiling of this ranch house) will likely attacked with blown in insulation, with careful attention to air sealing at the perimeter. I have lots of options up there, which all depend on how I tackle the walls. I certainly am factoring in the overall house assembly; the difficult part is assessing my options on the walls first, where I only have the interior of an existing block structure to work with.
Exterior insulation is not an option as the house already has original stone & stucco applied to the exterior of the block wall, and therefore that expense is not feasible.
Vapor drive, air sealing and achieving at least minimum code r-value on the wall is where I am struggling - because I have two key constraints: insulation must be add on the interior of the block walls, and the already small space has me looking to minimize that footprint. I could go with a 2x4" stud wall and closed cell foam, but is there a better or more cost effective option without stepping up to a 2x6 interior non-structural wall? Doing nothing is certainly an option (and kill the project!), but the goal of my original question is to understand the best way to handle the walls.
Tim,
It's possible someone who has experience with this type of building will chime in. In the meantime, see this article for more information: https://www.greenbuildingadvisor.com/blogs/dept/musings/insulating-old-brick-buildings