I've been negligent on posting my build thread, or maybe I should say, I've been negligent on finishing this never-ending project.
When I'm just about finished with the project, I'll post the build thread.
Anyway I've got two layers of 1-inch, R-6 rigid foam insulation on the walls and ceiling, and one layer on the floor.
I use a 12,000 BTU Atwood Hydroflame RV furnace. I also have a 1500 watt portable room heater that I use occasionally if we plug in somewhere. The Hydroflame gets it HOT. Last night it got down to about 20 F outside. I had the thermostat set to 65 F and the furnace cycled on and off all night. I would guess that it was on for about 5 minutes and off for about 30 minutes. The electric heater does okay too; it doesn't get downright hot, but it does an okay job of maintaining room temperature.
edit: here's my RV furnace:
http://www.atwoodmobile.com/furnaces/everest-star-7900-ii-series.aspWhat we've found over the last few months is that keeping the trailer warm is no problem. The bigger challenge has been moisture control. The build is not completely finished, so there are still a few exposed areas of metal framing and aluminum skin. Any metal that's exposed to the inside gets wet; I mean soaked with water. Eventually most of the metal areas will be insulated and sealed. As I'll show in my build thread I've been very conscious of creating a moister barrier. I just hope I did a good enough job.
More to come.