A Duct Moisture Problem Diagnosis (Short)

When there’s a gap that leads to the attic near the ductwork, the moisture can condense on the surface when cold air moves through the duct. Dust and grime can gather on the moisture-laden surface, and that’s when nasty growths start to form.

In this case, the solution is to replace the four-piece and seal off any gaps that lead to the attic.