Condensation problems on AC ductwork in attic
I added an AC system in my attic a couple of years ago and after having a couple of below zero temperatures I noticed my ceiling had a water stain on it. I found out it was coming from my cold air return main trunk. I then checked other supply and return branches and felt ice just underneath the foil side of the insulation. I have all solid ductwork with R-8 insulation. Last winter I had the same issue but in only one small spot on the 10" cold air return line which I was able to drain then reseal back up with foil faced tape. That problem was resolved by adding Reflectix cut to fit all air return and supply ducts, or so I thought until a few days ago. In the meantime I have vapor barrier that I have placed under the wet main return trunk until I can get some decent advice for fixing or how to fix this. I looked around on-line and saw that I should have used 2 layers of insulation but not double up on the vapor barrier. I sealed all the seams in the ductwork with mastic and taped all the seams with higher quality foil faced duct tape. Some of the tape has let go where it has leaked. Can anyone offer up some advice?