Both types air-seal your building in one pass — the difference is density, R-value per inch, and how they handle moisture. Here's how to know which one your job needs.
Spray polyurethane foam comes in two main forms. Open-cell is lighter and softer, fills big volumes cost-effectively, and lets water vapor pass through. Closed-cell is dense and rigid, delivers more R-value per inch, resists water, and stiffens the structure. Neither is "better" — they fit different jobs, and picking the right one is most of getting it right.
About half a pound per cubic foot. Roughly R-3.5 per inch. Expands big to fill cavities, dampens sound well, and is vapor-permeable — a cost-effective choice for interior walls and large attics where you have depth to fill.
About two pounds per cubic foot. Around R-6 to R-7 per inch. Acts as an air and moisture barrier, adds racking stiffness, and gives the most R in the least space — the workhorse for metal buildings, crawlspaces, rim joists and roofs.
Closed-cell packs more R into less space; open-cell needs more depth to reach the same R-target. Where framing depth is tight, closed-cell wins.
Closed-cell resists bulk water and acts as a vapor barrier; open-cell lets vapor through, which can be an advantage or a drawback depending on the assembly.
Closed-cell is rigid and adds racking stiffness to walls and roofs; open-cell stays soft and flexible.
Open-cell's softer, expansive fill is excellent at damping airborne sound in interior walls and ceilings.
Open-cell expands to fill large cavities affordably; closed-cell is the pick when every inch of R counts.
A layer of closed-cell against the sheathing plus a fill of cheaper insulation gets foam-grade sealing at a lower cost on the balance of the R.
Reach for closed-cell for metal buildings, shops, crawlspaces, rim joists, roofs, and anywhere moisture or a high R-value in a tight space matters. Reach for open-cell for interior walls and large attics where sound control and cost-per-cavity matter and vapor movement is fine. Not sure? That's what the free assessment is for — we'll tell you straight which one your job calls for and why.
Open-cell is lighter and softer with a lower R-value per inch and it lets vapor through; closed-cell is dense and rigid with a higher R-value per inch and it resists water. Closed-cell also adds stiffness to the structure. We match the foam to the job and tell you straight which one you need.
Usually closed-cell. It seals the metal, resists moisture and condensation, and adds rigidity — which is why it's the go-to for metal buildings, pole barns, crawlspaces and roofs in our region.
Closed-cell — it delivers more R-value per inch than open-cell, so it's the choice where space is tight or you need to hit a high R-target. Open-cell still air-seals well and is cost-effective where you have the depth to fill.
Yes — a flash-and-fill hybrid uses a layer of closed-cell against the sheathing for air, moisture and stiffness, then fills the rest of the cavity with a cheaper insulation to hit the R-target. It's a smart way to get foam-grade sealing without foaming the entire depth.
Spray Foam Insulation · Attic Insulation · Ice Dam Prevention · The Building Envelope · Foam Strengthens Walls · Crawl Space Encapsulation
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