In cold climates, can unvented roof assemblies rely on thick open-cell spray foam without exterior rigid insulation and still avoid wetting of the roof deck long-term?
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Relying only on thick open-cell spray foam without exterior insulation is risky in cold climates. It can work if done perfectly, but it’s not the safest or most code-friendly method.
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No,in cold climates, thick open-cell spray foam alone can let moisture reach cold roof sheathing and condense. To stay safe and code-compliant long-term, pair it with exterior rigid insulation, closed-cell foam, or a tested hybrid assembly.