Open Cell vs. Closed Cell Spray Foam — Which One Does Your Home Actually Need?

This is the question we get most often, and the honest answer is: it depends on where you're insulating and what you're trying to solve.

Closed-cell foam cures rigid and dense, with an R-value around 6–7 per inch. It acts as both an air barrier and a vapor retarder, which makes it the right call for crawl spaces, rim joists, below-grade walls, and anywhere moisture is a real concern. It costs more per square foot, and for those applications it's worth it.

Open-cell foam is softer, expands more aggressively, and comes in at R-3.5 to R-4 per inch. It fills irregular cavities extremely well, performs well for sound dampening, and costs significantly less than closed cell. For interior walls, vaulted ceilings, and attic assemblies where vapor permeability is acceptable, it's often the better choice — not a compromise.

The mistake most homeowners make is assuming one type is universally better. Closed cell is not always the right answer just because it has a higher R-value per inch. Using closed cell where open cell would do the job costs more than it needs to. Using open cell in a moisture-exposed application causes problems.

What actually matters is the building assembly — where the vapor barrier needs to sit, how much cavity depth you're working with, and what the moisture conditions are. That's what we look at before recommending anything.

If you're not sure which type your project needs, call us. That's a five-minute conversation and it costs nothing.

(845) 319-9169 | sprayfoamhv.com