What is the purpose of having an air barrier adjacent to insulation?

The purpose of having an air barrier adjacent to insulation is to eliminate convection around and through the insulation. When air moves through or around insulation, it can carry heat away from the insulated space, significantly reducing the effectiveness of the insulation. An air barrier serves to restrict this airflow, thus minimizing heat loss due to convective currents. By reducing convection, the overall thermal performance of the insulation system is improved, allowing it to maintain the intended thermal resistance (R-value).

When installed correctly, air barriers effectively create a more stable thermal environment by ensuring that the insulation can perform optimally without being compromised by moving air. This helps in maintaining energy efficiency in buildings and contributes to overall comfort levels by preventing drafts and cold spots.