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Community and Q&A

Masonry and spray foam (SPF)

Marcus De La Fleur | Posted in Energy Efficiency and Durability on

I am working on a deep energy retrofit for our 100+ year old building with a masonry shell. Rubble (limestone) foundation wall, followed by 3 wythe of common brick at up to the 1st floor ceiling, followed by 2 wythe of common brick through to the parapet.

From what I pieced together, I am thinking of using open cell SPF sprayed directly onto the masonry walls to insulate the entire building shell from the inside and attic (one contiguous layer that also acts as an air barrier). Open cell SPF seems the way to go to keep the perm rate high, allow vapor movement to the inside and out, and keep the drying potential of the masonry towards the inside. Closed cell foam may not give me enough vapor permeance and may cause long term damage to the masonry.

I have combed through this website (GBA) and BSC to figure out if open cell SPF is the way to go. I find a lot of good info for brick veneer and frame construction, including warnings about moisture management and vapor movement, but nothing that fits my solid masonry shell case.

Any advise, expertise, experience or other resources would be greatly appreciated!

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Replies

  1. J Chesnut | | #1

    Marcus,
    People will want to know what climate your house sits in in order to gauge the moisture dynamics of your proposed wall assembly.

    I would look to past Q&A discussions about thick spray foam applications and potential curing problems.
    Usually when the "deep" qualifier is used that means R-values in excess of 30+. This requires a thick spray foam application which there are concerns you should be aware of.

  2. Marcus De La Fleur | | #2

    J Chesnut, good point on the climate zone! My project is in Chicago IL.

    I will look through the Q&A's again.

    I plan on 3 inches of open cell foam on the walls to get the building air tight. Following the 3 inches of open SPF I plan on using recycled cotton batts or spray in cellulose to get my R-value to about 25.

  3. J Chesnut | | #3

    Marcus,
    A 3 inch application of open cell foam is not much of a concern when considering the curing process.
    I used open cell in a portion of my own home for the combination of airtightness and the ease of filling awkward spaces. I found it to be messy and I'm concerned about the environmental impacts of the industrial production of plastics. The open cell application performs fine but applications are never perfect and a blower door test with thermography reveal some minor gaps allowing air flow. In retrospect I would have used a dense pac cellulose for that area as I have just done for the rest of my house.
    Since your application is from the interior your attempts to establish a proper continuous air barrier is compromised by the difficultly of connecting the rim joist and roof joist conditions to an air barrier established by the spray foam application. You probably can achieve the same level of air tightness with a well sealed drywall layer and you can achieve the same R-value and vapor permeability with an only a cellulose fill, cellulose being a more benign and a less messy more predictable installation.
    I'm less confident on judging whether you'll run into any moisture problems with your proposed assembly.

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