Understanding Air & Vapor Barriers

All fifty U.S. states require a continuous air barrier as part of new construction. Code generally contains three compliance options for acceptable air leakage, or permeability, through an air barrier.

In spite of the ubiquity of requirements for air barrier usage, and increasing code standards, there remains a significant amount of confusion and misinformation in the roofing industry regarding air barriers and their distinctions, if any, from vapor barriers and vapor retarders.

Learn more about the definitions and performance characteristics of air barriers, vapor retarders, and vapor barriers. The white paper also outlines conditions where the performance of an air barrier has a significant impact on the overall building. 

Vapor barriers play a crucial role in high-performance roofing systems by limiting the diffusion of water vapor through building enclosures. These barriers prevent moisture-related issues, such as condensation and mold growth, ensuring the structural integrity and longevity of the roof. Selecting the right vapor barrier involves understanding its permeability and the specific needs of the building.

David Finley is the Director of Building Enclosure Science for The Garland Company. His building envelope investigative experience includes water infiltration testing of windows, curtain walls, masonry facades, and plaza and below-grade waterproofing; condensation and air leakage testing of glazed fenestrations and masonry facades; performing hygrothermal analyses using steady and transient state techniques; analyzing window and wall systems for two-dimension thermal conduction; and more.

David is active in ASHRAE Technical Committees 1.12, 4.4, and 160, and serves as the Program Chair and voting member for TC 1.12, voting member for TC 4.4, and Co-chair of the Freeze-Thaw Task Force for SSPC 160.