After modelling my own

[Bob VM]

There's a line in "Garbage Warrior" where they say, "You can't know if it's going to work until you build it, and you can't build many unless you have clients..."

There's a program called EnergyPlus that can be used in conjunction with Google Sketch-Up and OpenStudio to create models. I found that with unconventional buildings like an earthship the best thing to do is create a general model in OpenStudio (as a Sketch-Up plug-in) and then edit the surface constructions in the EnergyPlus .idf text file. If we're only concerned about thermal characteristics, then we can know in advance what will work...theoretically, because we know the surface materials.

So here are some conclusions:
- about 7cm of thermal mass near the surface is all that will be productive in affecting room temperature assuming you have like 1-2 cm of plaster on top of it. If you live in a cold climate like me, that means sticking bottles in the cracks of the wall isn't such a great idea, because the bottles or cans are hollow. Putting 1 meter of dirt behind the tires in front of the insulation has no more effect on temperature than if you put it right behind the tires, unless there is some other reason like to control drainage and keep it dry. If you have less, then it doesn't have the 7cm deep mass, then temperatures will fluctuate. This is an essential element in a passive solar house, but 70cm of rammed earth wouldn't hurt either. This means that thick tire sidewalls don't have much more affect on temperature than cement bottle walls, since cement has higher density than rammed earth to compensate for the holes.
- In a sub-arctic Mongolian climate 15cm of floor insulation is enough. The stock global model doesn't have floor insulation. If there is no floor insulation or less than 15cm here, it will be colder than +20C in the living space and probably no amount of thermal mass will help. Southern Canada is probably OK in many places. Here they technically have permafrost. Without floor insulation heat will constantly escape through the floor without insulation.
- The roof needs about 37.5cm (R-75?) of insulation here. 30cm or less probably without beefing up the floor insulation probably means it cannot sustain +20C.
- The thermal wrap insulation needs to be about 30cm here.
- Other essential things to maintain an environment where it is at least +20C all year without even a stove in Mongolia are thermal buffer zones, so the living space does not have direct contact with the outside world with air insulated space. This includes above below and behind and in front of the living space. The 3rd greenhouse is a good start. Airlocks to east and west are great. They should be exposed to sun so the tire walls can absorb heat and keep even the airlocks warm.
- Single pane glass lets in more sun. The glass must be covered with thermal curtains in cold weather implying vertical glass which hangs curtains well, but also catches indirect light of snow better, preferably on automated control. Thermal curtains can be R-10 or more. If it turns out things are too cold, then more curtains can be hung. If thermal curtains are not generally sealed off around the edges, then heat escapes.
- Non-insulated doors are thermal holes. Wooden doors must be insulated to contain heat.
- To keep thermal buffer zones, a good approach is to put glass in front of the living space. The vol. 1 approach doesn't have this. In cold climates there is no thermal buffer zone, so heat in the living space easily exits through the glass and a heater with all of its issues comes with it. I found that kind of stove was such a bother and time consuming. I would rather change the house to accommodate anything which would eliminate that burden.