Open-Cell vs Closed-Cell Spray Foam

Density. Open-cell is a soft, half-pound foam whose cells are open, so it stays lower density, air-seals well, and dampens sound — but it stays air-permeable and isn't a vapor barrier. Closed-cell is a rigid, two-pound foam whose cells are sealed shut, giving it a much higher R-value per inch, a built-in vapor barrier at sufficient thickness, moisture resistance, and added structural rigidity.

Closed-cell, by a wide margin. Closed-cell delivers roughly R-6.5 to R-7.0 per inch — the highest of any commonly available residential insulation — while open-cell is about R-3.7 per inch. That means closed-cell hits a given R-value target in roughly half the thickness, which is why it's the choice when cavity space is tight.

For most Oklahoma attics, open-cell applied to the underside of the roof deck is the standard recommendation. It costs less per inch, expands aggressively to fill irregular roof framing, and an attic doesn't need the vapor-barrier function that closed-cell adds. Closed-cell on a residential roof deck is usually more than the job requires. We'll confirm the right approach for your home during a free estimate.

Yes. Closed-cell foam acts as a Class II vapor retarder once it's sprayed to a sufficient thickness, and it resists water and condensation — which is why it's used in crawl spaces, metal buildings, and exterior or below-grade walls. Open-cell is air-permeable and can absorb water, so it air-seals beautifully but does not function as a vapor barrier. That's the single biggest reason to keep open-cell on interior, dry applications.

Closed-cell. Metal sweats — when warm interior air meets a cold metal surface, condensation forms and drips on whatever's stored inside. Closed-cell bonds directly to the metal, acts as a vapor barrier, and keeps the surface above the dew point so condensation never forms. Open-cell can absorb water and doesn't stop vapor, so it's the wrong choice for bare metal. The correct thickness depends on how the building is used and how cold it gets — we spec that during a free estimate.

Yes, and we often do. A common approach is closed-cell where moisture and rigidity matter — crawl space walls, rim joists, the metal envelope — and open-cell for interior walls, ceilings, and sound isolation where it delivers great performance at a lower cost. The best mix depends on your specific structure, so we'll walk the property and recommend the right foam for each area during your free on-site estimate.