Open-Cell Spray Foam vs Fiberglass: Which Provides Better Air Sealing?

Open-cell spray foam provides a better air seal than fiberglass because it expands to fill every gap and crack in a structure. While fiberglass acts as a filter that allows air to pass through, spray foam creates a custom-fit thermal envelope that stops drafts. This difference is the most important factor when comparing open-cell spray foam vs. fiberglass for home energy efficiency.