Direct answer
Closed-cell foam at 2"+ thickness IS a vapor barrier — no additional barrier needed. Open-cell foam is vapor-permeable; in cold climates, a separate vapor retarder may be required. Partner-network installers design per IECC code.
Authoritative sources
- US Department of Energy ↗
DOE Energy Saver guide to insulation types, R-values, and recommended applications.
- IRS Section 25C ↗
Energy Efficient Home Improvement Credit — up to $1,200/yr for qualifying insulation work.
- Energy Star ↗
Energy Star recommendations for attic and wall insulation R-values by climate zone.
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