When we built the barn in Dallas, discovered condensation had run down the metal roof to the purlins, then dripped on the hay. Ruined about 14 small squares.
I bought a bunch of terry cloth (what towels are made from) and attached to the purlins where they touched the roof.
Condensation would run down the metal roofing to the purlins where it was absorbed by the terry cloth. That ended the dripping problem.
Attaching it wasn't hard since the area was full almost to the roof with hay and I could stand on the hay and easily reach the purlins.