Asklemmy

How long would it take for the environmental cost (including CO2 emissions, and the inefficient use of resources associated with trying to live away from others) of the new building to be overcome by the savings in energy (and thus CO2 and associated environmental degradation involved in gathering those resources) when compared to just living in an already built house?

I'd wager that just maintaining an old house is better. Of course if you ignore everything else other than energy use and diverting something from a landfill, earth ships are very cool. Maybe not $10,000 either.

Its unclear whether one person building an earth ship instead of buying and maintaining an older house would make any positive environmental change.

Instead, if you took your $10,000 and partnered with others who have similar investments, you could build a small mixed use building which includes a couple shops on the ground floor, and dwellings on the next few floors (likely you would have enough combined to get a mortgage/loan to build). Why? Living in an apartment style building is going to be more efficient than any kind of single person dwelling (and you could use some of the earth ship ideas as well), having shops near homes would also help eliminate occasional car trips by having amenities right where you live. As a bonus, if this building was built for the investors to live in, you all now have equity and relatively low cost housing that is much easier to sell than an Earth ship in the middle of nowhere, should you ever need to move.