ARCC 3202 Chapter Notes - Chapter 9: Air Barrier, Vapor Barrier, Vapor Pressure
19 Jan 2016
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Document Summary
Confusion over air vs vapour barrier design and specification. Important not to stop the air itself from moving in an uncontrolled manner, but to stop its ability to carry water (in all forms) Air leakage is the leading cause of exterior wall problems. Linked to efflorescence, spalling masonry, ice build-up under soffits, frozen pipes, condensation in cavities. Rain penetration, high energy costs, poor control over indoor humidity. Terms: vapour barrier, vapour retarder, air/vapour barrier, elastic air barrier, wind barrier, pressure barrier, and air barrier preservative. Vapour barrier must stop, or retard, the passage of moisture as it diffuses through the assembly of materials in a wall. An air barrier must stop outside air from entering, and inside air from exfiltrating though the building envelope to the outside. This applies whether the air is humid or dry, since air leakage can result in problems other that the deposition of moisture in cavities.
