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air barriers - the history
"The history of air barriers can be traced to the early 70's 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.
More info of this article can be found on the web at:
http://www.henry-bes.com/airbarriers.asp