Warm Air Rises Into The Attic Through Small Gaps
Heat rises, and in a two-story house it pushes hard against the top-floor ceiling. It finds every gap: around pot lights, ceiling fans and bathroom fans, along the top of each interior wall, around the plumbing stack and the chimney, and around the attic hatch. Each one is small, but together they can add up to an open window.
Loose fill on its own never stops that draft, so attic air sealing goes in ahead of it. Loose fill slows heat moving through it, but warm air can flow right through the fibres.
Attic Air Sealing Keeps Frost Off The Roof Boards
The air leaking into a Barrie attic in winter is warm and damp. When it meets the cold roof boards, it turns to frost. On a sunny day the frost melts and drips back onto the insulation, and after a few winters the sheathing turns black with mould.
Attic air sealing stops that moisture at the ceiling. It is one of the main reasons we seal before we insulate, every time.
What Gets Sealed During Attic Air Sealing
We seal along the wall tops inside the attic, wire and pipe holes, pot light housings with covers rated for insulation contact, the plumbing stack, the gap around the chimney with fire-rated material, and duct boots in the ceiling. On the hatch, foam weatherstrip goes around the frame and a stiff foam board goes on top. Bathroom fans are checked to make sure they vent outside, not into the attic.
Attic Air Sealing Pricing
Attic air sealing on its own usually runs $400 to $1,500, depending on how many leaks there are and how easy they are to reach. Paired with new loose fill, sealing and insulation together tend to come in at $2.00 to $3.50 for each square foot. The attic insulation top-up page covers the layer that goes on afterward.