Hi. We experienced a similar problem once. Our first night out, 18
years ago, was in a blizzard at -4. We suffered major condensation.
Since that day we have never had a problem, even at temperatures down
to -14. We always leave the heater on, set at minimum, and have one
roof light open on vent. Also leaving the wardrobe door ajar solves
any "chill factor" when getting dressed in the morning.
Enjoy the weather and have a healthy New Year.