TinnerFlow™2nd YearYELLOW · Check First45° Elbow Vapor Barrier
Condensation usually means humid air is reaching cold metal through an air gap or broken vapor barrier. Dry it, tighten the wrap, and seal the vapor barrier continuously.
The outside heel of a cold supply elbow sees strong temperature difference. If the insulation has a pocket, loose wrap, torn foil, or open seam, humid plenum air can reach the cold metal and sweat.
Dry the metal and insulation area, rewrap tight to the elbow shape, and seal the foil/vapor barrier completely. If water got into the insulation, replace wet material instead of taping over it.
Do not tape over wet insulation or leave air pockets against cold supply duct.
Sweating duct can damage ceiling tile, create mold risk, and ruin insulation performance.
Final direction belongs to the foreman, approved drawings/specs, manufacturer instructions, pressure/material schedule, employer policy, and AHJ/code requirements.