I lived in a regular travel trailer for 2 or was it 3? winters. It was a 1970 something Kit Companion. I would think that the same things would need to be done to a
fiberglass trailer.
I had heat tape and insulation around the water hose. I knew to keep the water dripping. I did not know that the holding tank valve should be kept closed so I had it open. I was in a trailer park with full hookups.
I had plywood skirting.
I blocked half the
windows with
fiberglass batting.
I had a locker rented for frozen food elsewhere because the
refrigerator would not work once the weather got into the 20s. I used a cooler, kept outside for a
fridge.
The
propane furnace refused to work. I had a space heater in the front of the trailer and one in the back of the trailer in the bathroom. Even with heat, it was freezing at the feet and quite warm at head level.
I would wake up sometimes to find frost on the inside of the walls. Cooking anything that needed simmering was out of the question due to condensation. I had no exhaust fan.
I had mold damage to a sleeping bag that I had kept hanging in a closet.
Luckily, the winters were balmy for the Methow Valley during those years. I think it only got down to +3. I finally found a house to rent, and it was a good thing because the next few winters were normal with below zero temps.