That's one of the nice things about masonry (and mud, dirt) walls that thick. When humidity is high they absorb moisture, when humidity is low they give off moisture. It can help regulate humidity.

The thermal mass of the walls must really soak up some heat. It doesn't look like there is any insulation on some of the wood ceilings. Seems like there would be a lot of heat loss out the windows and ceiling.


EDIT: so further research shows that there is fair amount of insulation.
http://youtu.be/wTqSpx0Vgv4

In years past I helped build a couple of rammed earth houses and an adobe house here in Ontario. No insulation was necessary, the rammed earth walls were 2 ft thick and the source of heat was a masonry wood stove. It didn't need anything else, other than solar for power and for DHW.

There is a great BSC paper on earth as insulation. I'll dig it up and post a link to it tomorrow when I have time.


EDIT:

http://www.buildingscience.com/docum...er-green-roofs