Thickness of Closed Cell Insulation in 2×4 Walls
I’ve built a 200 sq ft structure (tiny house on wheels, not inspected) with 2×4 walls and 2×6 rafters. I’m ready to insulate and have been planning on using closed cell spray foam for the whole thing to avoid moisture issues in the unvented cathedral ceiling. (I would love to use Roxul instead if it were an option). I don’t have any can lights or skylights in the ceiling and only one penetration for the range hood.
My climate is 5A.
I’ve received several quotes for the closed cell. The first company suggested I only do 2″ in the walls since it wasn’t being inspected, which surprised me. He said that each additional inch of foam after that only gains you a fraction of what the first 2″ gets you(?)
I do like the idea of having a little bit of space to run a wire or move an electrical box if I have to do that at some point, but I don’t want to spend thousands of dollars to end up with the same R value as a fiberglass batt wall. My walls are already very tightly constructed (All exterior plywood panel edges land on blocking and are glued and screwed, so there is really no place for air to penetrate)
This company also suggested 4.5″ in the ceiling. The other companies suggested 3″ in the walls and 5″ in the ceiling.
I am inclined to do 2.5″ in the walls and 5″ in the ceiling, but please let me know if there are any other factors I’m not considering.
This is the installer I’m looking at right now (not the one who suggested 2″). Would someone with a better knowledge of spray foam installation quality mind taking a look at their portfolio and telling me whether their closed cell installation jobs look good?
Thanks very much!
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