We lived in a 27' 5th wheel trailer one winter here in NE OK with temps down to zero however as most plain states the issue is the wind when its cold.
The 5er had a 13' superslide. I bought mobile home skirting and skirted it all around except for the above bedroom.
I also made inside storm windows from 1/8" Lexan from Lowes. It came in 4' x 8' sheets. I added 3/8" thick foam for a gasket.
My water inlet was on 10' long so a garden hose wrapped in insulation and a heat tape with a thermostat worked fine.
My 3" sewer drain was 22' long and a good slope for fast drain into my house septic system but liquids didn't set so it wasn't wrapped with anything.
The biggest issue we has was condensation on interior walls and windows and mostly inside the closets. We tried the usual crack a window and or a vent. All that did was make the heater run 24/7 and a cold wet drafty camper. Our fix was two dehumidifiers from Lowes.
Read all you can on condensation causes in a RV. Its a big issue in a std trailer with just R7 floor/walls and roof with a aluminum frame and foam insulation.