Hey guys. I posted a few weeks ago about an issue I had where the supply trunk off the air handler was sweating in my finished basement. Not a drop ceiling, all drywall so I can't see what's going on exactly, can only see what's pictured below before trunk runs above drywall. All vents are open throughout house and basement. Hasn't sweat in a couple weeks after I left doors open to my "mechanical" room and opened basement supplies now today sweating on supply trunk is back! Granted it's 84 out with 70% humidity outside. Here's the facts: 1) my new LG 70 pt humidifier runs constantly and pulls about 1.5 gallons out in about a full 24-28 hr before its full. My basement humidity is never above 50% in any spot. 2) I peeked above ceiling drywall for further sweating but it looks like the supply trunk is only sweating where it's exposed in that room (about a 8Ft run pictured and ONLY spot that the cold supply runs about 1/4" parallel with the return-it splits off right where it disappears above drywall) 3) The BIG question---(just dawned on me today, Could it be the return trunk causing the sweating on the supply trunk due to its extreme close proximity to each other?(1/4") I'm thinking the temperature difference between the two because this is the only spot of duct trunk sweating. Tested humidity in that room and it's 39%! Another thing is that it's only sweating on that side-next to the return trunk! The side that's butted against the drywall wall is bone dry! Please offer any thoughts. Thanks!