A friend and I lived in our trailer & fifth wheel one winter in Montana.My trailer was only 24 ft.& had double pane windows.We stayed in a mobile home park & heated with electric.The trailer was boxed in with rigid Styrofoam,heater under the trailer(never used),heat taped and insulated a rigid plastic water line and sewer line & foam in the vents.I was working in Butte(very cold sometimes -20)and my wife stayed with me(no slides very cozy).We were pretty comfortable as long as you did not lean on the walls.We even had a built in thermometer.You could tell how cold it was by how high the frost went up the door.I was working many hours a week so the size of the trailer was not an issue.All in all we would say that it was a good experience but that was when electricity was cheap ,15 yrs ago.Now that we have a 30 footer with three slides it maybe not as easy to do.