At -20 c up here in Canada, I had to run my wood stove full throttle before I insulated. One side of me was cooking, the other side freezing.
Now I run the stove one 10th of that to keep warm.
My current set up is a bit different than most of you will have. The original bus shell is my interior, and I insulated on the out side with 6 inch fiberglass bats, then skinned with roofing tin. My outer metal skin never touches the inner skin, creating the thermal break to avoid condensation and heat loss.
Now lets talk about thermal mass of various materials.
Rigid Styrofoam has almost no thermal mass, and there for is what I will call "Thermal neutral. This means, no matter how much heat or cold I expose it to, the Styrofoam will not soak it up, and radiate it back into the room.
Wood is in the middle of this list. It is a insulator, but not a good one. It still contains enough thermal mass to take the heat or cold and radiate it back into the room. Just not very well.
Materials like steel have large thermal mass numbers. It absorbs the heat and cold and radiates it back into the room.
My wood / coal stove works well for me because of my inner steel shell. The stove radiates the heat into the steel, the steel holds the heat, and radiates it back into the room.
If I had a Styrofoam interior, my stove would not work well. The stove could only heat the air, and air has almost no thermal mass. Heating air is the most inefficient way to heat.
My new bus I'm building, "The Four Season Prime" will have no thermal mass anywhere except the floor. The floor uses sheets of 14 ga steel laying over the hot water heating lines as a subfloor. This steel will grab the heat from the heat transfer plates the water lines lay in, and radiate it up into the living space.
Thermal mass is good and bad. A cement shop floor contains large thermal mass. It can take days to bring up to temp, but also takes days to cool. This is not ideal due to if you get it uncomfortably hot, the floor takes time to cool down. This is why I was careful when engineering how much thermal mass to build into my floor.
I don't like propane heaters due to the danger, and the awful moisture they give off. Lorna likes her propane heater over the electric due to the moisture in the air increasing the thermal mass. The right amount of moisture is good, but too much is bad. All electric heaters give off extremely dry air.
Radiant heat is what makes life on this planet possible. The radiant heat from the sun travels millions of miles to earth. On this path it passes right through area's of minus 4000 degrees C, but it still gets here.
Air being a having almost no thermal mass and being a poor transmitter of heat and cold is what makes insulation work. Tiny air pockets trapped inside the insulation is what stops the transmission of the heat and cold.
So all in all, Thermal break, and thermal mass are what you need to know.
"Don't argue with stupid people. They will just drag you down to their level, and beat you up with experience."
Patently waiting for the apocalypses to level the playing field in this physiological game of life commonly known as Civilization