POLY VAPOUR BARRIER

A poly vapour barrier is an essential but often overlooked part of a well-insulated building system. This layer of polyethylene plastic sheeting is installed on the warm side of insulated walls, ceilings, and floors to prevent indoor moisture from entering the building envelope. In cold climates, warm indoor air carries moisture that can seep into cavities and condense, leading to mold, mildew, rot, and structural damage. The poly barrier stops this by blocking vapour migration, keeping insulation dry and effective. For the barrier to work properly, seams are overlapped and taped, edges are carefully sealed, and penetrations around outlets, wiring, and plumbing are caulked or foamed to create a continuous protective layer. When combined with batt or blown-in insulation, a poly vapour barrier helps homes meet building codes while also preserving long-term performance and durability. Though hidden behind drywall, it is one of the most important safeguards in keeping a home healthy, energy-efficient, and structurally sound. Skipping or improperly installing this step can undermine even the best insulation system, which is why professional installation is key.