Side-by-side specs
| Spec | Open-Cell | Closed-Cell |
|---|---|---|
| R-value per inch | R-3.5–3.8 | R-6.0–7.0 |
| Cost per board foot | $0.45–$0.70 | $1.00–$1.50 |
| Vapor permeability | Permeable | Vapor barrier above ~1.5" |
| Density | 0.5 lb/cu ft | 1.75–2.0 lb/cu ft |
| Best for | Interior walls, attic ceilings in mixed climates | Crawl spaces, rim joists, basements, coastal/hot-humid climates |
Open-Cell
Pros
- Lower cost per board foot
- Expands more — fills voids and odd cavities
- Lets walls dry in either direction
- Better sound dampening
Cons
- Lower R-value per inch (R-3.5–3.8)
- Absorbs water if flooded
- Not a vapor barrier
Closed-Cell
Pros
- Highest R-value per inch (R-6–7)
- Acts as vapor & air barrier
- Adds rigidity to wall assemblies
- Resists bulk water
Cons
- Roughly 2x cost of open-cell
- Can trap moisture if assembly leaks
- Less forgiving of substrate prep
Which should you pick?
- Crawl space, basement, or rim joist: Go with Closed-Cell. Moisture resistance matters more than cost.
- Insulating an attic ceiling on a budget: Go with Open-Cell. More inches of R-value per dollar.
- Coastal / flood-prone area: Go with Closed-Cell. Closed-cell won't absorb water if you get water intrusion.
- Soundproofing an interior wall: Go with Open-Cell. Open-cell's lower density absorbs sound better.
Frequently asked questions
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Next steps
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