Open-Cell vs Closed-Cell Spray Foam: Which Should You Choose?
The two main types of spray foam behave very differently. Your choice depends on where you’re insulating, your budget, and moisture concerns.
Open-cell spray foam
- Lower density, softer, expands more
- Cheaper per sq ft
- Great sound dampening
- Vapor-permeable (breathable)
- R-value ~R-3.5 to R-3.7 per inch
Best for: interior walls, ceilings, and attics where budget and soundproofing matter and moisture isn’t a concern.
Closed-cell spray foam
- Dense and rigid — adds structural strength
- Higher R-value ~R-6 to R-7 per inch
- Acts as an air and moisture barrier
- More expensive
Best for: crawl spaces, basements, rim joists, and any area exposed to moisture or where you need maximum R-value in minimal thickness.
Quick verdict
Need top performance and moisture resistance? Go closed-cell. Insulating a large interior area on a budget with soundproofing? Open-cell. Many US homes use both, depending on the location.