Keep my garage moisture free

Pole building 40x60x12 that bubble wrap under the metal siding and roof. 6x6 beams 8 ft on center. I put 2x6s 4 ft between beams then used 6” thick fiberglass battens 24” wide stapled together to make 4ft then 1/2 osb ply over that osb in the ceiling but no insulation up there yet. Still get a little moisture in the summer so I’m thinking of some type of air flow (no windows) 80 thousand btu oil furnace and two 110 ac window type units on each end of building. I can keep it 70 year round in Va