A true four season trailer or as close as possible

Sounds like my elkridge. Not a thicker roof, but a well insulted roof with a small attic space. Heated enclosed underside. We were in -26 Celsius over Christmas and didn't have any issues. At - 28 c the radiant heat from the 5er wasn't enough and our propane stopped flowing. I fired up the geny and put a space heater in the basement. Mine was.one of many custom orders for Alberta oil field workers.