Compare
Open-Cell vs Closed-Cell Spray Foam
Both are polyurethane foam, sprayed on site, and that is where the similarity ends. One is light and absorbent, the other rigid and impermeable — and the assembly decides which belongs there.
Side by side
| Criterion | Open-cell | Closed-cell |
|---|---|---|
| R-value per inch | Around R-3.5 | Around R-6 |
| Air sealing | Yes | Yes |
| Vapour control | No — remains permeable | Acts as a vapour retarder at sufficient thickness |
| Water contact | Absorbs water | Resists water |
| Installed cost per sq ft | $1.50 – $3.50 | $2.50 – $5.00 |
| Sound absorption | Better | Good, but less absorbent |
| Structural rigidity | Soft, flexible | Rigid, adds stiffness |
Choose open-cell when
- The space is interior and dry
- Sound control between rooms matters
- You need volume filled economically
- There is depth available to reach the R-value target
Choose closed-cell when
- The assembly touches the outside — rim joists, crawl spaces, foundation walls
- Depth is limited and you need R-value per inch
- Moisture or water contact is possible
- The surface is irregular and needs to be sealed as well as insulated
Questions
Can I mix both in one house?
Frequently that is the right answer — closed-cell where moisture and depth are constraints, open-cell in dry interior cavities.
Is closed-cell always better?
No. It costs more, it is less forgiving to install, and in a dry interior cavity with plenty of depth it buys you nothing over open-cell.
Still not sure?
You do not have to decide. Tell us what the space is and what you want it to do — the recommendation is part of the free assessment, in writing, with the reasoning.
