I agree insulation is important, but I am not sure it will turn the tables on -10 degrees for any period of time and I can’t imagine how much condensation would be running off the windows and maybe the walls. Having camped below freezing in a number of RVs, surviving is not an issue, but I found comfort certainly was!
My two cents
Steve and Andra
2012 F350 6.2 gasser SRW LB
Fab Fours front and rear in case we run into a rhino
2019 Northstar Laredo SC