HouseChalk
Closed-cell foam
Closed-cell foam is a dense type of spray foam insulation that acts as both insulation and a vapor barrier.
Why it matters
It has a higher R-value per inch and adds structural strength. It can be useful in tight spaces and in areas where moisture control matters.
Where people get this wrong
Closed-cell foam is more expensive. It may not be needed everywhere. In some wall assemblies, closed-cell foam can trap moisture if not designed correctly.
Real-world example
Closed-cell foam is sprayed into a rim joist area. It seals air, insulates well, and stops vapor from moving through the assembly.
Where this hits your build
This affects comfort, energy costs, and indoor air quality. It gets locked behind drywall, so decisions here need to be right before finishing starts.
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