# In cold climates, can unvented roof assemblies rely on thick open-cell spray foam without exterior rigid insulation and…

**URL:** <https://home.renovation.reviews/t/in-cold-climates-can-unvented-roof-assemblies-rely-on-thick-open-cell-spray-foam-without-exterior-rigid-insulation-and/20093>\
**Category:** Trade Talk\
**Created:** [August 4, 2025, 3:43pm UTC](https://home.renovation.reviews/t/in-cold-climates-can-unvented-roof-assemblies-rely-on-thick-open-cell-spray-foam-without-exterior-rigid-insulation-and/20093 "2025-08-04T15:43:30Z")\
**Posts on this page:** 3\
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**Author:** ![reno\_questions](https://home.renovation.reviews/user_avatar/home.renovation.reviews/reno_questions/32/2758_2.png) [@reno\_questions](https://home.renovation.reviews/u/reno_questions)\
**Post date:** [August 4, 2025, 3:43pm UTC](https://home.renovation.reviews/t/in-cold-climates-can-unvented-roof-assemblies-rely-on-thick-open-cell-spray-foam-without-exterior-rigid-insulation-and/20093/1 "2025-08-04T15:43:30Z")

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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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**Author:** ![Tim\_Michael1](https://home.renovation.reviews/user_avatar/home.renovation.reviews/tim_michael1/32/6294_2.png) [@Tim\_Michael1](https://home.renovation.reviews/u/Tim_Michael1)\
**Post date:** [August 7, 2025, 11:36am UTC](https://home.renovation.reviews/t/in-cold-climates-can-unvented-roof-assemblies-rely-on-thick-open-cell-spray-foam-without-exterior-rigid-insulation-and/20093/2 "2025-08-07T11:36:42Z")

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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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**Author:** ![Lexi\_Carter1](https://home.renovation.reviews/user_avatar/home.renovation.reviews/lexi_carter1/32/2767_2.png) [@Lexi\_Carter1](https://home.renovation.reviews/u/Lexi_Carter1)\
**Post date:** [August 11, 2025, 12:03am UTC](https://home.renovation.reviews/t/in-cold-climates-can-unvented-roof-assemblies-rely-on-thick-open-cell-spray-foam-without-exterior-rigid-insulation-and/20093/3 "2025-08-11T00:03:12Z")

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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.