You either have to increase flow of air through the rig by running a vent fan somewhere or get a dehumidifier. The problem with running a vent would obviously be trying to keep warm while circulating in fresh air. The problem with most dehumidifiers is the noise. I've had several dehumidifiers through the years and I've only found one that's quiet enough for me. The brand is Soleus but the problem with them is their reliability is terrible. One lasted me for two years and the next one only lasted a year. But man, they were very quiet and they kept the humidity under control very nicely. So good luck in your quest.
2015 Greyhawk 29MV
Honda CRV toad with Blue Ox baseplate
Ready Brute Elite towbar with braking system
TST 507 Flowthru TPMS