Do I need ignition barrier for spray foam in attic kneewalls?
So I outlined our attic insulation plan here, which was flash and batt with foam furring following by drywall in the occupied space:
We have had the closed cell foam installed (R22) and we are now considering the option of having 8″ (R36) open cell foam put instead of the original mineral wool. The areas that are getting drywall as a thermal barrier would still get furred with foam and strapped for drywall installation.
In the kneewalls, front dormer, and above the ceiling, the ocSPF would be left to encapsulate the framing. There is ductwork running in the front dormer (furnace soon to be ducted minisplit is within the dry walled space). Do we need an ignition barrier in these spaces?
I was thinking we would need an ignition barrier, but our installer says that we don’t. It likely isn’t enforced locally. So regardless of the inspector, what should we do?
The product we are looking at using is Demilac Agribalance. The evaluation report is here: https://www.demilec.com/documents/Tech-Library/ESR-Updates/ESR-2600-Agribalance-050118.pdf
Section 18.104.22.168 describes installation in attic spaces without an ignition barrier and I believe our situation meets all the requirements, but maybe I am missing something.
Any reasons we should stick with the original plan with mineral wool? This does seem like a lot of foam in the roof. It seems like the ocSPF should offer somewhat better performance, particularly in the awkward sections. We go from a R35 total wall to R40 and also move the labor from me to someone else for a $.025/R/SF premium.
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