9/8/2023 0 Comments Exterior building envelopeThe National Building Code of Canada (NBC) and the International Residential Building Code (IRC) set forth minimum resistance to airflow requirements for materials and assemblies. This layer is assembled from multiple components and can transition from different materials or components in the roof assembly to the wall assembly. Uncontrolled air leakage can lead to uncomfortable spaces for occupantsĪn air control layer is almost never comprised of a single material or component.Increase in energy consumption to maintain interior conditions for occupants.Development of condensation as air cools and deposits moisture within the layers of the building enclosure.There are three main reasons as to why it’s important to control air flow across the building enclosure, they include: “Air control layers control airflow between a conditioned space an unconditioned space or between units in multi-family and apartment construction”. However, this all depends on the moisture load available in the cladding. For a ventilation space will need much more than 1/16 of an inch (1.5MM), typically at minimum ¾ – 1” (20 – 25MM). Why? Because claddings can store water and this water can be driven towards the building enclosure via an inward vapour drive.Ī ventilation space between the cladding and the water control layer helps to disconnect the flow of the vapour drive. It is also recommended to ventilate the space between the back side of the cladding and the front face of the water control layer. This space can be as small as 1/16 of an inch (1.5MM). To help control the movement of rainwater a drainage plane can be incorporated into or provided on top of the water control layer to help direct water out and away from the building enclosure. It is typically the second line of defence (first is the cladding, but the cladding leaks, hence the need for a secondary line of protection) and can be located on top of the exterior sheathing, behind exterior insulation, or integrated into the front face of the exterior sheathing and/or insulation. “A sheet, spray or trowel-applied membrane or material layer that controls the passage of liquid water even after long or continuous exposure to moisture”.Ī water control layer is intended to control the penetration of rainwater into the building enclosure.
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