I have heavy condensation in the insulation surrounding my supply duct near at least one vent in my house.
Summer heat and humidity are high here - South Carolina
What could be causing the condensation?
What is/are the fixes?
are you able to visually see or if in the attic, actually feel the moisture in the insulation?
if the insulation is not tight around the ducts or there are air leaks, especially with metal ducts, there will be some condensation formed due the temperature differentials and it will drip onto the insulation.
or is "vent" you mention actually inside the house, in a ceiling register?
condensation is on insulation surrounding metal duct work.
The area on duct work and insulation that I can see and feel condensation is just before the duct work makes 90 degree up to the vent/register in wall.
duct work is under house - in crawl space.
I would have to check to see how tight the insulation is around duct work. The duct work and insulation have been in place longer than I have lived in house - more than 13 years.