ADD COMPLETE VAPOR BARRIER! Plastic seal edges and double thickness of
10 mil plastic.

Make certain no extra water is getting dumped under home things like
route downspouts well away from area! Adding a ground water drain under
and away from home with gravel under house can be used for tough or
standing water situations...

OPEN ALL VENTS and add more vents so air flows easily under home!

REMOVE AND FORGET about dehumidifiers, they arent needed in this
application and will just increase your electric bill dramatically!

If your really intent on spending money on electric add a ventilating
fan with humidistat so it only runs when the humidity is high!