Closed cell spray foam delivers R-6 to R-7 per inch, the highest R-value of any common insulation, and it doubles as a vapor barrier at 2 inches of thickness. For Utah County homes in climate zone 5, that makes it the best choice for rim joists, where the floor framing sits on top of the foundation, plus basement walls, garages, and any space where moisture is a concern. Closed cell foam is installed across Provo, Orem and the rest of Utah Valley by independent providers. Call (801) 691-7136 for a price range.
What Closed Cell Foam Does
Closed cell foam cures into a dense, rigid material. The cells in the foam are sealed, which is what gives it three properties no other insulation matches in one product:
- R-6 to R-7 per inch. Fiberglass batts run about R-3.2 per inch. In tight framing cavities, closed cell fits double the insulation value into the same space.
- Vapor barrier built in. At 2 inches, closed cell foam qualifies as a class II vapor retarder, meaning a layer that lets only a small amount of moisture pass through it. No separate plastic sheeting, no gaps.
- Structural rigidity. Closed cell foam bonds to framing and sheathing and measurably stiffens walls and roof decks.
How It Is Used in Utah County Homes
Rim joists are a common closed cell job in Utah Valley. The rim joist is the band of wood where your floor framing meets the foundation, and in most local homes it is either bare or stuffed with loose fiberglass that does nothing to stop air. Two inches of closed cell foam seals and insulates it permanently. Other common applications: basement walls before finishing, garage ceilings under bedrooms, cantilevered floors, and metal buildings.
How Does Closed Cell Compare to the Alternatives?
The properties that matter in a Utah County basement or rim joist are R-value per inch, whether the material stops air, and whether it needs a separate vapor barrier. The costs in the last row are per board foot, which is one square foot of foam at one inch deep:
| Closed cell foam | Open cell foam | Fiberglass batts | |
|---|---|---|---|
| R-value per inch | R-6 to R-7 | R-3.6 to R-3.9 | about R-3.2 |
| Stops air leakage | Yes, completely | Yes, completely | No |
| Vapor barrier | Built in at 2 inches | No, vapor permeable | Separate install |
| Safe against concrete | Yes | No | No |
| Adds structural rigidity | Yes | No | No |
| Installed cost | $1.00 to $1.70 / board foot | $0.45 to $0.75 / board foot | Lowest |
What Does Utah Code Require for Basement Walls?
Utah has adopted the 2021 IECC. For climate zone 5, which covers all of Utah County, basement walls require R-15 continuous insulation, or one of the equivalent assemblies the code allows. At R-6 to R-7 per inch, roughly 2.5 inches of closed cell foam meets that on its own, with the air seal and vapor control included rather than added as separate layers.
Code adoption and local amendments vary, so confirm with your city or county building department before finalizing a basement finish. For every other assembly the numbers are different again, and we break them all down in our Utah insulation code requirements reference.
Closed Cell Pricing FAQ
How much does closed cell spray foam cost?
Closed cell spray foam typically costs $1.00 to $1.70 per board foot installed. A board foot is one square foot at one inch deep. A typical rim joist job in a Utah County home runs $1,000 to $2,500 total. See spray foam insulation cost in Utah for how board foot pricing turns into a project price.
Is closed cell worth the extra cost over open cell?
It depends on the space. Below grade, against concrete, or anywhere moisture is possible, yes, closed cell is the only foam we recommend. In a vented attic where space is not tight, open cell often gives more R-value per dollar.
How thick should closed cell foam be in climate zone 5?
For rim joists and basement walls in Utah County, 2 to 3 inches is standard. That delivers roughly R-13 to R-21 plus the air seal and vapor barrier, which meets or beats code requirements for those assemblies.