Land Yacht cold/ warm capabilities
I have a 97 wide body Land Yacht and recently traveled from MN to AZ and back. I experienced temp swings from -10 to 85 degrees. On my rig the wall and ceiling insulation is quite good. The limiting factor seems to be the single pane windows, they let in more cold than the walls or ceiling. But nothing that the furnace can't handle. I have also noticed that my rig stays cool when closed up in the summer, even when it is in direct sunlight.
I just drove 3,500 miles, ran like a top and got pretty goog mileage; 10-11 mpg with diesel fuel ranging from$3.59 to $3.89 per gallon.