Vapour Barrier Installation Blue Quill Edmonton

Poly and air sealing in Blue Quill before the board goes on

A vapour barrier only works as a continuous plane. In Blue Quill the failures are almost never the sheet itself — they are the electrical boxes, the top and bottom plates, the window returns and the penetrations, where the poly is cut and not resealed.

• Electrical boxes poly-hatted and sealed
• Left ready for inspection before boarding
• Poly on the warm side of the insulation
• Window and door returns detailed properly
• Seams lapped at framing and sealed, not just taped
• Rim joists air-sealed before insulating

Vapour Barrier Installation Blue Quill Edmonton

Sealing at the electrical boxes

Blue Quill drywall in context

Basement walls, where the rules change

Where the barrier meets the ceiling and the floor

Seams belong on framing

The parts an inspector looks at first

The rim joist and the bottom plate

Simple, clean, on schedule — Vapour Barrier Installation in Blue Quill Edmonton

Vapour Barrier Installation Blue Quill Edmonton: your questions answered

Should I use poly or a smart membrane?

Most straightforward Blue Quill walls are fine with 6-mil poly, continuous and sealed. A variable-permeance membrane is worth it on retrofits and some basement details because it gives the assembly a drying path in both directions.

Is a basement wall done the same way as an upstairs wall?

No. A basement wall can take moisture from the ground too, so poly detailed like an above-grade wall can trap moisture against the concrete. The insulation is held off the concrete so the wall can dry, with vapour control on the warm side.

Why is there staining around my window reveals?

Usually the vapour barrier return at the window was torn or tucked rather than sealed. It is a cold junction, so condensation shows there first — often as staining or mould at the reveal.

Is the vapour barrier the same as an air barrier?

Not by itself. Poly slows vapour diffusion; sealed properly it also slows air, and unsealed it does very little of either. The sealing is what turns a sheet of plastic into a working assembly.

What about outlets on exterior walls?

Each one is a deliberate hole. They need poly hats or airtight boxes sealed to the sheet. Taping poly to the front of an ordinary box does not last once board is fastened over it, and it is the most common leak we find.

Does it matter where the sheets overlap?

Yes. A lap must land on solid framing and be sealed with acoustical sealant compressed between layers. An unsupported lap taped across a cavity flexes with pressure changes and works loose.