Dome freezing

[Skibum]

New to the crew but have read all previous posts, thanks for the help, living in a 30' pacific yurt on an insulated platform with reflectix insul. When the temps get below 5 degrees Fahrenheit, the

dome

freezes overnight and then drips in the morning. This is with ventilating during the day, ceiling fan 24 hrs, bathroom vented outside, woodstove and mostly electric appliances. We are in the Tetons and when the temps go into the negatives the

dome

gets worse, even with constant venting and humidity below 17% in the dome. What to do? I don't have a screen insert with my fan, so I can't put plastic on the screen easily. Any help?