Insulation · 6 min read
Open-cell vs closed-cell spray foam
Neither foam is universally better. The right choice depends on the assembly, the moisture strategy and what the space is used for.
Open-cell
Lower density and vapor-open. It fills irregular cavities well, is less expensive per inch of thickness, and allows an assembly to dry inward — which matters when a roof leak eventually happens.
Closed-cell
Higher density, higher R-value per inch, and a vapor retarder at sufficient thickness. It adds rigidity and is often chosen where space is limited or where moisture control demands it.
How we choose
We look at the roof assembly, the space limitations, the moisture strategy and the intended use of the area — then specify the foam that suits it rather than the one we happen to prefer.
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