Video answer · Seal Tech Insulation
Open-Cell or Closed-Cell Spray Foam: Which Does My Project Need?
Choose closed-cell where moisture is a concern or you need the most R-value in a thin space.
✓ Answered by the Seal Tech crew✓ Serving SE Michigan since 2000★ 4.7 · 270+ Google reviews
The short answer
Choose closed-cell where moisture is a concern or you need the most R-value in a thin space. Choose open-cell in clean, dry spaces where sound control and value matter. Many homes use both.
What the crew says in the video
- Closed-cell foam is denser (about 2 lb density) and more resistant to moisture.
- At about an inch and a half, closed-cell gives you a true vapor retarder. Open-cell does not.
- In a clean, dry space, open-cell performs better on the everyday noise you notice in your home.
- Open-cell is fluffy and soft, and you can still have a wonderfully insulated home with it as long as the structure is sound.
Open-cell or closed-cell: side by side
| Closed-cell | Open-cell | |
|---|---|---|
| Feel | Hard, rigid | Soft, spongy |
| R-value per inch | About R-6 to R-7 | About R-3.5 to R-3.8 |
| Moisture | Resists moisture; vapor retarder at about 1.5″ | Not a vapor retarder; use in dry spaces |
| Sound | Good on low-frequency noise | Better on everyday, mid-to-high-frequency noise |
| Cost | Higher per square foot | Lower per square foot |
Where Seal Tech usually uses closed-cell
- Rim joists and basement foundation walls
- Crawl space walls
- Exterior walls where you want the most R-value in a 2×4 cavity
- Metal buildings and pole barns, where condensation is a risk
Where open-cell is often the better value
- Attic rooflines and cathedral ceilings in dry, well-built assemblies
- Interior walls and floors between rooms, for sound control
- Deeper 2×6 walls, where open-cell has room to reach a strong R-value
On most projects the answer is not either/or. We look at each area of the house separately and often use both.
Further reading: Where to Insulate in a Home (U.S. Department of Energy).
Seal Tech tip: Not sure which you have now? Press on it. Open-cell squishes like a pillow; closed-cell feels like a board.
Get the right foam in the right place
We will walk your project and recommend open-cell, closed-cell, or both.