A word of warning.
People sleeping in a confined space exhale water vapour. FACT
If the ambient temperature is low then the coldest areas within a California are the Cabin windows ( normally single glazed ) and exposed body panels in the wardrobes and kitchen cupboards which are not insulated. FACT
If you get condensation on the Windscreen overnight then you have inadequate ventilation. FACT
If you have condensation and then use an insulated Windscreen cover and you get NO condensation without any increase in ventilation then all you are doing is shifting the condensation to the next coldest areas - the exposed body panels within the wardrobe/kitchen units and behind any body trim.
Get the ventilation requirements correct first and then use the windscreen cover.
Use Disposable Humidifiers, at least 2 or 3 within the vehicle and you will collect a surprising amount of water if the ventilation is not correct when sleeping.