Insulating and Air Sealing Large Openings, Shafts, or Drop Ceilings

Large openings in the ceiling plane, such as for service shafts or drop ceilings, can be a major cause of air leakage in attics.

This air sealing procedure is for openings in the ceiling plane running perpendicular to the ceiling joists. Where the opening runs parallel, a similar procedure can be used with some adjustments.

A relatively large hole in the ceiling plane through which two ducts are installed.
Spray foam around the edges of a cover, sealing it to surrounding joists and ceiling gypsum board.

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