Very interesting what you say about Earthship housing, I didn't know about it, I was researching about it last night. I was struck by the wide walls to maintain a comfortable temperature inside. In my country, in the area of Paraguaná I knew mud houses with very wide walls, they put doors and small windows, the idea was to keep inside the cool environment and prevent the penetration of hot air from outside.
The problem of our time is more of lifestyle than of population. Solutions such as the houses you propose are a great alternative. Be well dear @eco-alex. A big hug from Maracay.
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yes earthships are next level in terms of keeping warm or cool.. so much thermal mass its not comparable to much else.. up to 6 feet of it at the back!