Open-Cell vs Closed-Cell Spray Foam: Use Product and Assembly Data

Obtain the product’s declared thermal resistance, density or other relevant properties, permitted substrates, application limits and protective-covering instructions. Do not assign one universal R per inch to either category. Vapor-control behavior and air-control suitability depend on the product, thickness and complete assembly.

Roofline and wall applications can have different ventilation and drying requirements. NRCan’s material guidance is useful context, while the product technical documentation governs installation details. A foam thickness estimate cannot certify moisture behavior.

For an example product entered at US R-7 per inch and a custom R-14 target, thickness = 14 / 7 = 2 in. Over 100 ft² this is 200 board feet before losses. These numerical values illustrate the target-R method; they are not published as a property of every closed-cell foam.

If another actual product declares a different resistance at the permitted application, use its data and recalculate. Apply a separate yield allowance and round complete kits or quoted units. Do not combine one product’s thermal value with another’s yield.

Identify substrate condition, application thickness, environmental limits, protection, access, cleanup and required finish layers. Compare the complete project rather than the category name or a generic square-foot price. Confirm the installer’s verification method for finished thickness and the product instructions governing the application. The calculator provides quantity from supplied data, not a universal recommendation between foam categories.