Do you guys ever advocate wrapping the exterior of supply plenums with batt insulation?
This one year warranty inspection has had issues with condensation (4 story, single system, three zone, no variable blower or bypass duct/barometric damper observed) lot’s of staining on the decking below. The builder has “addressed” the issue by adjusting slope of the plenums, installing a pan which extends past the plenums (new pan has rust staining) and wrapping the plenums with fiberglass batts.
I always considered this a “band-aid” solution for the symptom that masks an underlying problem (e.g., damaged / displaced insulation board inside the plenum, improper configuration of the system, etc.) rather than a proper fix. In my experience the fiberglass traps moisture against the outside of the plenum and promotes rust.
I’m interested in your expert opinions.