Air sealing is the process of identifying and closing gaps, cracks, and unintended penetrations throughout a building envelope, addressing the uncontrolled air movement responsible for energy loss, comfort issues, and potential moisture problems that insulation alone doesn’t fully resolve.
This work typically involves caulking, foam sealant, weatherstripping, and specialized gaskets applied at the many small and large gaps that accumulate throughout typical residential construction, from framing connections to utility penetrations.
Energy auditors often prioritize air sealing before adding insulation, since sealing air leaks first ensures that any subsequently added insulation performs as intended rather than being undermined by continued uncontrolled air movement through the same assembly.
What Does Air Sealing Involve?
- Caulking or foam sealant at gaps and penetrations
- Weatherstripping at doors, windows, and attic hatches
- Sealing around recessed lighting and other fixtures
- Addressing rim joist and other structural transition gaps
Why Is Air Sealing Important?
A home with excellent insulation but poor air sealing can still lose substantial heat through uncontrolled air movement, which is why building science increasingly emphasizes air sealing as at least as important as insulation thickness in achieving genuine energy performance improvement. This is a common gap in many renovation projects that focus heavily on adding insulation while overlooking the equally important sealing step.
A blower door test, which depressurizes a home to identify air leaks, is a valuable diagnostic tool for locating specific air sealing opportunities that might not be obvious through visual inspection alone, helping prioritize efforts toward the locations with the most significant impact. This sequencing, sealing before insulating, tends to produce measurably better overall energy performance.
Air Sealing vs. Air Leakage
Air sealing is the solution, the process of closing gaps and penetrations. Air leakage is the problem, the uncontrolled air movement through those same gaps, which air sealing work is specifically intended to address and reduce.