Closed-cell spray foam in exterior wall of home in zone 4A (mixed-humid) – GreenBuildingAdvisor

Hi, I’m an avid reader and intermediate-level building science nerd. I’ve searched and searched but couldn’t find info on my specific situation so I was hoping someone could help me.

I live in Northwest Arkansas (Zone 4A) and would like to insulate my unconditioned garage wall as part of a larger garage-insulation effort. I was considering using closed-cell spray foam leftover from another DIY project but after much researching am unsure if it’s a good idea. The insulation is DAP 600FR dual-tank kit. I’d spray to achieve at least 2″ thickness. Details below:

Wall Assembly (exterior to interior):

brick cladding

1″ airspace

Exterior sheathing (black-colored sheathing original to the 1975 house)

2×4 stud wall, studs 16″oc

1/2″ drywall (painted)

I’ve read Builder’s Guide to Mixed-Humid Climates (atleast 10x) and understand the issue in our region of needing to dry in both directions but I worry about the closed cell and potential for it acting as a double vapor barrier. Although the unconditioned garage reduces the temperature differential between interior/exterior which I would think reduces condensation risk so maybe the CCSPF is okay in this particular condition. I then learned about brick heat drive and now I’m worried about that, given the wall is south-facing wall and gets beat with the sun throughout the day.

I could insulate the wall with unfaced batts instead if that’s a more resilient option, but I have this extra spray-foam that would otherwise go to waste. I just don’t want to shoot myself in the foot by creating a moisture trap that destroys the wall in a few years. Is using CCSPF a bad idea? Can you help me? I’d greatly appreciate it!! GBA Rocks

Will