November 11, 2026 · Pocatello Insulation

Spray Foam vs. Fiberglass: Which Is Right for Your Home?

Both work. The right choice depends on where it's going, your budget, and what problem you're trying to fix.

R-value per inch

Closed cell spray foam is about R-6 to R-7 per inch, open cell about R-3.5 to R-3.8, and fiberglass batts about R-3 to R-3.5. In a thin wall or a rim joist, closed cell gets you the most insulation in the least space.

Air sealing is the big difference

Fiberglass slows heat moving through it, but air passes right through it and around it. Spray foam expands into gaps and seals them. In a windy place like the Portneuf Valley, stopping drafts often matters as much as the R-value number.

Cost

Fiberglass and blown-in insulation cost less up front. Spray foam costs more, but it also air-seals in the same step. Many of our best-value jobs combine the two: foam at the rim joists and tricky areas, blown-in insulation in the open attic.

When each one makes sense

Choose closed cell foam for metal buildings, crawl spaces, rim joists and anywhere moisture is a problem. Open cell works well for interior walls, sound control and attic rooflines. Fiberglass and blown-in are a solid, affordable choice for open attics and standard framed walls.