I can only meet part of your qualifications to answer this and that was (although slim), the possibility of 2' of snow but temps hardly ever below 10 above zero. I stored my Lance camper, a toy hauler and a travel trailer in Oregon over a period of several years. The absolute best advice anyone ever gave me was NO plastic and an oil heater that I kept on the low watt and setting of 2. It stayed on 24/7 the entire winter and even during long periods of rain in the spring. A lightbulb is not enough. When I started doing this my rigs kept the new smell for years and no more musty smell.