AIR LEAKAGE THROUGH Exterior joints and top and bottom plates

Pay attention to improper sheathed walls and unsealed junctions. They are important air leakage sources.

Exterior joints and wall junctions are often connected to cavities - wall cavities, sub floor cavities and ceiling cavities. There are many construction flaws in all these areas, mainly in wood-frame homes, causing serious air leakage problems.Air Sealing Joints

Sealing these potential or very real causes of air leakage is crucial and very rewarding in terms of energy savings. The image at right (from DOE) illustrates key elements of that sealing…

Mechanisms of air infiltration

The wind may easily penetrate the ceiling (mainly cathedral ceilings) through the soffit vents, where weaker elements like recessed fixtures may facilitate air leakage.

Air and elements can also enter into wall cavities through improperly sheathed walls or at the top plates of interior and exterior walls. You should seal along the seams, at the top of interior wall cavities. These are locations where large amounts of air use to leak, through penetrations connecting the wall cavities and the attic.

The air can also enter into floor cavities through bottom and top plates, via junctions or other weak elements in the wall and framing structures…

Construction flaws are the main explanation for these types of air penetration in the wall-ceiling-floor hidden cavities. Pay attention to them. They are between the most important causes of energy inefficiency, discomfort and high energy bills due to air leakage.

The sealing

Use a proper sheathing to avoid air penetration through the wall surfaces and junctions. Bottom plates of exterior walls should be sealed with caulk (or with gaskets). Do not forget to caulk the inside edges also.

You may apply drywall to the top and bottom plates. Band joists should be sealed with spray foam, or caulk or gaskets (between band joists and top plates and band joists and sub-floors).

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