I have to build a concrete base for a summer house in my garden.  I had a bit of an idea that I might dig down and actually build a concrete bunker underneath while I was at it, in order to house some miners.  Just wanted to find out whether anyone has actually done this themselves, and what solutions they had for heat, air, soundproofing?  Electricity and internet connection should be easy enough.

Or is it an unfeasible idea?