How to Seal Attic Air Leaks

Sealing Attic Air Leaks

Introduction:

Air leaks or air infiltration, is the number one source of unwanted air entering or leaving your home. Air infiltration cost you money by driving up heating and cooling cost. Even if your attic floor is adequately insulated with high quality attic insulation there is likely air leakage around vent pipes, chimneys and other attic openings. These opening must be sealed to prevent air leakage.

The ceiling in your home separates the living space from the attic. It appears to be a solid surface but the truth is that ceilings leak air into the unfinished attic spaces through gaps and openings around pipes and lighting fixtures. Warm air in winter and cool air in summer that is leaking into your attic is costing you approximately 25 to 30 percent of your home energy cost due to air leaks. That can amount to approximately $200 to $300 dollars a year depending on the size of your home. To eliminate these air leaks you must find them and eliminate them by filling them with insulation. An attic entrance cover is a big source of air leaks.

Finding and sealing attic air leaks:

Electrical connections for ceiling fixtures such as fans and lights require a hole that is cut out in your ceiling drywall. Each of these cut outs is likely leaking air. Stop the air leaks by sealing the cutouts from inside the attic with acrylic latex or silicone caulk, or with low-expansion polyurethane foam.
Check around anything that penetrates the ceiling such as pipes, vent stacks, flues and chimneys, heating and air conditioning ducts and the access hatch cover. Seal any gaps around these locations from above.
Plug large gaps with low expansion polyurethane foam. It is great for gaps that are ¼ inch to 3 inches wide that are often found around plumbing pipes and vents. Plug small gaps with caulking for gaps that are less than ¼ inch wide such as those around electrical boxes.
Seal air leaks around flues and chimneys but be careful. Building codes require that all wood framing be kept at least one inch from metal flues and two inches from masonry chimneys. Unfortunately this space creates gaps where air can flow through into or out of the living space. You can cover the gaps with aluminum flashing cut to fit and sealed into place with high-temperature silicone caulk. You can also stuff the area with fire resistant insulation.
For attic access hatch leaks install foam weather stripping around the perimeter of the hatch opening.

By eliminating these attic air leaks you can save a great deal of money on heating and cooing cost.

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