Humidity or condensation? For condensation, sometimes it’s the dreaded balance of vent/window opening amount and how much cold you are letting in. Bigger duvet, more vent opening! I have found that ‘cracking’ windows or a vent is not enough to reduce condensation. I fear you may be in a losing battle trying to reduce humidity from the levels outside.
2007 Dodge 3500
[5.9 Cummins, Stick Shift] + [XPCamper V1E]