From my limited understanding that I'm not bothering to go back and research, they didn't use insulation at all until fairly recently. There was only extremely localized heating like that blanketed table thing and that worked fine until the west came over, first with battleships and later with nukes. Most modern houses, I think I read, are built like prefab western shit if you're not rich as hell.
Ha I just installed one of these. That's a 0 toilet seat. The heated seat is really nice and the water and air are also heated. The deodorizer smell like cow shit though.