HouseChalk
Spray foam insulation
Spray foam insulation is a liquid that expands and hardens on contact, filling cavities and sealing air leaks at the same time.
Why it matters
Spray foam can air seal and insulate in one step, which is why it performs well in many assemblies. However, it can be more expensive and mistakes are harder to fix.
Where people get this wrong
Open-cell and closed-cell foam are different. Closed-cell is denser and a vapor barrier. Open-cell is softer and breathes more. The right choice depends on the location and climate.
Real-world example
Foam is sprayed into a rim joist area. It expands to fill every gap and hardens. No separate air sealing step is needed because the foam does both jobs.
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.
Most people do not just struggle with terms. They struggle with the decisions tied to them.
See how HouseChalk helps with the decisions behind terms like this