I have a custom Phoenix popup camper, built for the Canadian winter. Most popups offer an arctic package for the popup portion. Mine is two layers of a Thinsulate knock-off sandwiched between two layers of fabric. The hard walls are 2" thick with rigid styro insulation
I carry water in 2.5 gallon collapsible jugs and I use RV antifreeze instead of water in the porta-poti.
I heat up water on the stove and use a "Hot Juggz" primitive shower which is a 2 gallon pump-up plant sprayer with a low flow shower nozzle and pressure release valve. I can shower with less than 2 gallons of water!
I have a 18k btu furnace and a 2000watt Honda generator so I can turn the furnace off while charging the 2 AGM batteries and also run a 1000watt heater or a heat gun if needed. I almost never need to use my electric mattress warmer.
I have 2 20lb propane tanks.
I have been able to maintain 65F inside when it is 0F outside.
Ready, set, let's go skiing!