i never ran a dehumidifier or anything, moisture levels were never really an issue. at most, i had very minor frost on some windows when it was really cold. other than that, all good!
the electric heater maybe helped, but i would usually blow the hatch in the bathroom during showers and that seemed to keep moisture minimal. their was a few times where it was really cold and we just got a dump of snow (here goes my procrastination again) and i didnt shovel the roof, so i couldnt use the vents. at that point their was a noticable increase in moisture(nothing extreme), thats when the windows would develop the little bit of frost at the corners.
'14 XLR 395AMP
'16 Ram 3500 DRW, 6.7 cummins w/aisin trans and 4.10 gears