Side-by-side specs
| Spec | Spray Foam | Blown-In |
|---|---|---|
| R-value per inch | R-3.5 (open) to R-7 (closed) | R-2.2 (fiberglass) to R-3.8 (cellulose) |
| Typical installed cost | $1.00–$5.00 / sq ft | $1.00–$2.75 / sq ft |
| Air sealing | Yes — built-in | No — separate step required |
| Settling | None | 10–20% in attics over 5–10 years |
| Lifespan | 80+ years | 20–30 years |
| Moisture resistance | Excellent (closed-cell) | Fair |
| Best for | Walls, crawl spaces, rim joists, roof decks | Open attic floors, dense-pack wall retrofits |
Spray Foam
Pros
- Acts as insulation AND air barrier in one application
- Highest R-value per inch (R-6 to R-7 closed-cell)
- Won't settle, sag, or absorb moisture (closed-cell)
- Adds structural rigidity to walls and roof decks
Cons
- 2-3x more expensive than blown-in per sq ft
- Requires licensed installers and curing time
- Difficult to remove if you remodel later
Blown-In
Pros
- Lowest installed cost for attics
- Fast install — typical attic done in a few hours
- Fills around wiring, framing, and irregular cavities
- Made from recycled cellulose or fiberglass
Cons
- Does not air seal — needs separate sealing work
- Can settle 10-20% in attics over time
- Lower R-value per inch (R-2.2 to R-3.8)
Which should you pick?
- You're insulating an unfinished attic floor: Go with Blown-In. Blown-in gives the best R-value per dollar for open attics. Pair with air sealing first.
- You need to insulate AND stop air leakage in one step: Go with Spray Foam. Spray foam is both insulation and air barrier — fewer trades, faster project.
- You're insulating a crawl space or rim joists: Go with Spray Foam. Closed-cell spray foam resists moisture and won't fall down like batts.
- Tight budget, biggest energy impact per dollar: Go with Blown-In. Blown-in at R-49 in the attic beats partial spray-foam jobs for ROI.
Frequently asked questions
Related comparisons
- Open-Cell vs. Closed-Cell Spray Foam
- Fiberglass vs. Cellulose Insulation
- Batt vs. Blown-In Insulation
- Rigid Foam Board vs. Spray Foam
- See all insulation comparisons
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Local pricing and licensed contractors for Spray Foam in these metros.
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