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Apprentice answer

Why does an uninsulated fresh-air louver sleeve drip condensation

2nd YearInsulation, Liner & CondensationCheck first

Cold intake sleeves through humid spaces need insulation/vapor control. Dry the metal, seal air leaks, and wrap the sleeve with the approved vapor-tight insulation detail.

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Plain-English answer

A fresh-air sleeve can carry cold outside air through a warm humid plenum. If the metal sleeve is exposed, humid air can condense on it and drip onto ceiling tile or drywall.

Check for missing insulation, open vapor barrier seams, air leaks, and cold metal contact. Wrap/insulate the sleeve per the mechanical insulation spec and seal the vapor barrier continuously so humid air cannot reach the cold metal.

Ask Foreman

The outside-air sleeve at [location] is sweating above the ceiling. I checked the wrap and the metal is bare/cold. Do you want it insulated with the project vapor-barrier detail?

Verify before acting

Use this as training guidance. Foreman direction, approved drawings, project specs, manufacturer instructions, employer safety policy, and AHJ/code requirements always control the final answer.

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