Understanding the Basics of Spray Foam Insulation
Spray foam insulation comes in two main types — open cell and closed cell.
Both are made from polyurethane and expand when sprayed, but they differ in structure, density, and performance.
Knowing which one to use can help you save money, increase comfort, and improve your home’s energy efficiency.
💡 If you’re new to spray foam, start with our Complete Guide to Spray Foam Insulation.
What Is Open Cell Spray Foam?
Open cell spray foam is a lightweight, flexible insulation with cells that aren’t completely closed.
This makes it softer, more breathable, and ideal for interior spaces.
Key Features
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Density: ~0.5 lb/ft³ (very light)
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R-Value: ~3.6 per inch
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Expansion Rate: High — fills cavities easily
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Best For: Interior walls, soundproofing, and hard-to-reach corners
Advantages
✅ Great sound absorption
✅ Expands more, requiring less material per area
✅ More affordable per board foot
✅ Easy to trim and shape
Limitations
❌ Lower R-value than closed cell foam
❌ Not moisture-resistant — not ideal for basements or exteriors
❌ Requires vapor barrier in humid climates
What Is Closed Cell Spray Foam?
Closed cell foam is dense, rigid, and highly resistant to air and water.
Each tiny bubble (cell) is completely sealed, giving it strength and superior insulation value.
Key Features
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Density: ~2 lb/ft³
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R-Value: 6.5–7.0 per inch
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Expansion Rate: Low — denser coverage
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Best For: Garages, attics, rim joists, basements, and crawl spaces
Advantages
✅ Strong vapor & moisture barrier
✅ Highest R-value among insulation types
✅ Adds structural strength to walls
✅ Prevents mold, mildew, and condensation
Limitations
❌ More expensive than open cell foam
❌ Less sound absorption
❌ Slightly harder to trim or shape
Side-by-Side Comparison Table
| Feature | Open Cell | Closed Cell |
|---|---|---|
| Density | 0.5 lb/ft³ | 2 lb/ft³ |
| R-Value per inch | ~3.6 | ~6.5–7.0 |
| Soundproofing | Excellent | Moderate |
| Moisture Resistance | Low | High |
| Rigidity | Soft / Flexible | Hard / Rigid |
| Cost | Lower | Higher |
| Expansion | Greater | Limited |
| Best For | Interior walls, soundproofing | Attic, garage, basement |
Which One Should You Choose?
The right choice depends on where and why you’re insulating:
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Choose open cell if you’re focused on sound control or finishing interior walls.
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Choose closed cell if you need moisture protection, strength, or high R-value insulation.
🏠 Our Recommendation:
For most U.S. climates, closed-cell spray foam like Bigrizy Guard Spray Foam Insulation gives the best balance of performance, lifespan, and energy efficiency.
Cost Comparison
Open cell spray foam typically costs $0.50–$0.70 per board foot, while closed cell runs around $1.00–$1.50 per board foot.
Even though closed cell is pricier upfront, it often pays for itself in long-term energy savings.
Read more about that here:
👉 Spray Foam Insulation Cost Breakdown: What You Need to Know Before You Buy
Environmental & Safety Notes
Modern formulations like Bigrizy Guard’s are low-VOC and Class A fire-rated.
Regardless of type, proper ventilation during application is crucial.
Once cured, both types are safe, stable, and odor-free.
For more on safety, see → Is Spray Foam Insulation Safe? Facts You Should Know Before Applying
Final Thoughts
Both open and closed cell spray foam offer excellent benefits — the key is matching the right type to your project.
If you want durability, strength, and maximum energy efficiency, closed cell is the way to go.
If you’re soundproofing or working on interior walls, open cell may be your better fit.
