Our experience --- 3 months winter-camping in a wide variety of ski resorts in British Columbia, California, Utah, Colorado, and New Mexico --- suggests that you may not need a double-walled trailer in order to stay overnight at ski resorts without freezing your pipes or building up too much interior condensation.
This past March, when we spent a week in our Casita
(17' SD model) at Whistler in British Columbia, temperatures fell well below freezing each night and stayed that way until noon most days. We prepared for this by:
- wrapping a water pipe heater hose around the 10-foot potable water hose that connected us to city water and insulating it with pipe foam insulation, to prevent the city water from freezing in the hose
- running a 1500 Watt ceramic heater 24 hours a day (if we had not had shore power, we could have run the propane
furnace) to keep the interior of the trailer warm
- keeping the center roof vent, covered with a MaxxiVent, open at all times to vent any moisture-laden air
- keeping the bathroom vent and bathroom door open to help interior air-flow and venting
- being meticulous about running the Fantastic Fan and the stove vent fan whenever we were using the propane
cooktop or the electric coffeemaker, to vent moisture
- NOT cooking things, like pasta, that involve boiling a lot of water
- keeping all of the upper and lower cabinet doors open during our absence on the ski hill
- NOT using the trailer shower
We were found no condensation buildup on the trailer windows
and completely dry walls.