Speaking as someone who had three (of ten) projects on the LEED awards list in 2005, sustainability is a noble goal but unless you've got a serious power generator (your own personal wind farm, a noteworthy waterfall on the property), going for zero is a fool's errand. The real-world, technical term for your sketch is a ground source heat pump. a company I used to work for was the leader in GSHP design for the pacific northwest. They're pretty conventional once you get over the installed cost (2x-5x conventional heat pump designs). They also work better if you hang the radiator in a lake rather than digging into the ground. The real-world, technical term for your waste-water ambitions is greywater. "crazy insulated" matters a lot less than passive solar design. What you'll discover when you dig into it is that all these things can be accomplished without going crazy... but the guys who do it tend to not wear it on their sleeve. The goal is to make something efficient while also livable.