Closed Cell vs. Open Cell Spray Foam

These are two fundamentally different materials with different properties and applications. For commercial roofing, only one is appropriate.

Closed-Cell Spray Foam

Density: 2.8–3.0 lb/cu ft. R-value: 6.5 per inch. Cell structure: closed cells that are impermeable to air and water. Properties: rigid, strong (25–60 PSI compressive strength), waterproof, acts as vapor barrier, UV-sensitive (requires topcoat). Applications: roofing, foundation walls, cold storage, any application requiring structural strength and moisture resistance.

Open-Cell Spray Foam

Density: 0.5–0.8 lb/cu ft. R-value: 3.5–4 per inch. Cell structure: open, interconnected cells that allow air and moisture to pass through. Properties: soft, flexible, low strength, absorbs moisture, allows vapor diffusion. Applications: interior sound dampening, attic insulation in certain climate zones, interior air sealing. NOT appropriate for roofing or exterior applications.

Why the Distinction Matters for Roofing

Open-cell foam would be catastrophic on a commercial roof — it absorbs water, provides minimal structural support, has inadequate R-value, and would soak up moisture from any leak rather than resisting it. Any contractor proposing open-cell foam for a roofing application should be disqualified immediately. Only manufacturer-approved, roofing-grade closed-cell SPF is appropriate for commercial roofing.