Thought i'd start a new question to see if I can get any new ideas. Overview:
E. PA location. 2 year old new construction home, approx 1200 sq ft, open concept first floor (so all supply and returns run through exterior walls). Basement is unfinished and unconditioned. We have a heat pump and central ac (2 ton). The basement is dry.
Last summer we noticed one specific supply duct in the basement at the front of our house condensating at the corners of the wall where it goes up to the main floor of the house, when it's hot and humid outside. (This duct runs up and bends and goes through the floor in both front bedrooms to floor registers, 2nd floor). All of our other ductwork in the basement is dry and has never done this. The dripping isn't constant, it seems to come and go.
Things we have tried so far: -We run a dehumidifier in the basement, set to 45%. -We change filters seasonally and they are never really that dirty. -I got a thermometer w/a humidity sensor and the temp is steady at 67 with 44% humidity in the basement. -I have tried adjusting the dampers with no change. -We had our blower fan speed checked and it was on low (we moved it up to high, still dripping, although it's not any better or worse than before). -We've looked in the vent at the top of the duct that drips the most and the duct is clean with no signs of water inside (felt dry, no signs of dust pooling where water may have been, no white chalky stuff, etc). -Condensation seems to get worse when we run the clothes dryer in the basement, which is a new discovery last night. -We have tried adjusting the thermostat anywhere between 71-74 and it drips regardless. -We have checked the vapor barrier by cutting the living room wall open where the duct is (on the worse side). There was insulation behind the duct facing the correct way but we stuffed it full with additional insulation just in case). There was no sign of moisture anywhere, either on the duct or on the back of the drywall.
I had to live w/a torn up living room for months until I was able to get it respackled, repainted, etc so I am hoping for the least invasive problem and repair, if possible. Do any of these things sound like they could be it or fix the issue? -conditioning the basement air (we want to finish the basement anyway, which why this issue is a current priority). -wrapping the duct (how do we know this isn't just a bandaid and will seal condensation inside?) -Could our hvac unit be oversized? -Possible issue with our ac unit? (It is still under warranty)
Any other thoughts or opinions are appreciated.