Henry #1 Choice of Professionals: Air & Vapor Barriers

Air leakage is the uncontrolled movement of air through the building envelope. This movement of air is caused by wind, stack effect, and fan pressures. The combined forces are significant and must be resisted by the air barrier system. Uncontrolled air leakage translates into:

   • Uncontrolled heat loss
   • Uncontrolled cooling costs
   • Increased humidification needs
   • Condensation problems
   • Mold and serious indoor air quality concerns

These issues have proven to be significant enough to effect building code changes. Air barrier technology is a rapidly growing concern for all designers and specifiers, and Henry® leads the industry with over 18 years of experience with successful, high profile projects.

With over 17 completely integrated systems, our architectural services team can assist building owners, designers, and specifiers create an effective plane of air tightness throughout the building envelope.

Theory On Air Barriers

The history of air barriers can be traced to the early 70s during the energy crisis. Building professionals were looking for ways to make buildings more energy efficient and eventually realized this could be achieved by stopping uncontrolled air leakage through the building envelope. The term "air barrier" was quickly adopted.

Air Barriers were first incorporated into the National Building Code of Canada in 1986. In the United States, requirements for air barriers can now be found in the Massachusetts Energy Code. Many other states and ASHRAE are currently planning to incorporate requirements for air barriers in their next code revisions.

An air barrier must first and foremost resist air leakage. The loads involved are more significant than many designers realize. The Massachusetts Energy code, section 1304.1.2, states and air barrier shall "have an air permeability not to exceed 0.004 cfm/ft2 under a pressure differential of 0.3 in water." Testing of air leakage is based on American Society for Testing of Materials (ASTM) E283, E330 and E2178. In these tests, a mock-up wall is constructed and covered with a membrane. The mock-up is then subjected to air pressures ranging from 1.6 lb/ft2 to 62 lb/ft2. The air leakage through the membrane is measured at all pressure levels and is inspected for visual delamination. All Henry air barriers have been tested by independent testing laboratories.

Air Barrier membranes can be categorized in the following two types of air barrier:
1. Vapor Permeable or 2. Non-Permeable.

1. Vapor Permeable Air Barriers:

Henry vapor permeable air barrier membranes resist air leakage and rain penetration through the building envelope. However, since they are vapor permeable, they allow the diffusion of moisture, in the form of vapor. Therefore, they are not vapor barriers. In essence they can let the walls of your building "breathe." Vapor permeable air barriers offer designers more flexibility in the positioning of the air barrier within the wall assembly.

2. Non-Permeable Air Barriers:

Henry non-permeable air barrier membranes resist air leakage, rain penetration, and vapor diffusion. Therefore, they act simultaneously as an air barrier, a vapor barrier, and a rain barrier. Since these membranes also act as a vapor barrier, the positioning of non-permeable air barriers within the wall assembly is critical in avoiding potential condensation problems.

Refer to our vapor permeable air barrier or non-permeable air barrier web page for more information on the available Henry air barrier membranes.