What is an important feature of air barrier materials used in construction?

An important feature of air barrier materials used in construction is that they must be flexible enough to accommodate building movement. During the lifecycle of a building, various factors such as temperature changes, settling, and dynamic forces can cause movement in the structure. If an air barrier material is rigid, it may crack or become compromised over time, leading to air leaks and reduced energy efficiency. Flexibility allows the air barrier to maintain its integrity, ensuring that it continues to prevent unwanted air infiltration and exfiltration, and thus maintains the building's energy performance and comfort.

While water resistance, thermal mass, and chemical resistance may also be relevant properties for certain materials in construction, they do not directly address the critical need for accommodation of movement specific to the function of air barriers.