Maxxair covers on every roof vent & leave the vents open solved our humidity problem two RVs ago. Presently we are using Maxxair IIs on our current rig. The vents have remained open since the day I installed the covers.
Dave, Judy & Daisy May
2010 Sierra 356RL
2011 Silverado 2500 4WD, LT, Ext Cab, LB
Duramax 6.6L V8 Turbo Diesel
Allison 1000 6-Speed Automatic Transmission