Rapid City, SD
Closed-Cell vs. Open-Cell Spray Foam in Rapid City, SD
Which foam is right for each part of your project, and why it matters more in this climate.
Open-cell foam is lighter and less expensive (about R-3.5–3.7 per inch) and is vapor-permeable — a good fit for interior walls and sound control. Closed-cell is denser, runs about R-6–7 per inch, and acts as its own air and vapor barrier, which makes it the standard for rim joists, crawl spaces, pole barns, and anywhere moisture is a concern.
Most whole-building projects here use both: closed-cell in the moisture-exposed and space-constrained areas, open-cell where sound and budget matter more than maximum R-value per inch. For a single-purpose job — one pole barn, one attic — the right answer comes down to the assembly and what it's exposed to.