Back in the 70s and 80s, and especially after the OPEC oil embargo when people were thinking they might freeze to death when the oil ran out in any given winter, there was a whole thing with "earth sheltered housing," where people were experimenting with building houses below ground, sort of along the lines of the zombie-proof house in HH's thread re the million dollar prepper house, but more below ground and with offset skylight setups. Supposedly , even in Canada you coud heat the whole place just through the normal use of appliances and lightbulbs etc. There were books written about it, but I don't know anyone who did it. Has anyone encountered or considered such a place? I always thought they would have EOTWAWKI defensive virtues as well as the design purpose of being heat efficient.