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markstg 09-30-2013 06:15 PM

Wet attic duct insulation
My ac ductwork in the attic, round sheet metal, has gotten soaking wet from condensation. The AC contractor is coming out tomorrow to fix the low Supply Air and low cfm problem (the complete system is under warranty). The undersides of the duct are wet like a wet baby's diaper.

Does the wet insulation need to be replaced?

Gary in WA 10-03-2013 10:56 PM

If there was any organic matter on the pipe or in the insulation before it got wet, that substance could mold. Eg. carrying the insulation out of the van setting on dirt/ground, setting it on dirty attic floor/other insulation, etc. Mold cannot thrive on fiberglass alone and it will dry out to retain the R-value. Hopefully they install a vapor barrier over the insulation after air-sealing the pipe joints with tape/mastic w. mesh tape. Mastic/tape the ends of the v.b./insulation to stop all warm outside attic air from infiltration to condense on the colder AC ducts. IMO, replace any showing sag/wetness to start fresh worry-free.

Wet f.g. in a wall will lose 60-70% of R-value;


Windows on Wash 10-12-2013 12:04 PM


Gotta seal all the joints to start with and once you have controlled the air loss, we typically bury them in insulation keep the condensation at bay.

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