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Polyethylene has been one of the most common barriers used in construction in the last 40 years. When installed carefully, it was meant to act as both a vapour barrier AND an air barrier, cutting the amount of time and money that a contractor has to spend to ensure airtightness.

"Poly" is still used in modern construction, and is still one of the least expensive ways to meet code requirements for vapour barrier and air barrier. But to make very air tight buildings with polyethylene proves to be more challenging than some alternatives.

Important Considerations for Polyethylene:

• Used for many decades as a vapour barrier and air barrier
• Common and inexpensive material - installation method is well known to most contractors
• Requires careful attention to proper fastening, adhesives and 'clamping' of polyethylene - with lumber strapping, for example - to resist wind pressures from exterior through assemblies
• Openings and penetrations in polyethylene must be carefully cut and coupled with the use of appropriate tapes, gaskets and sealants.
• Overlaps and intersections must be sealed properly to ensure continuity of vapour and air barriers