I'm not entirely sure what section of this forum to post this question in. For money reasons, I've determined it unwise for me to spend upwards of $20k for a geothermal unit in this house since I won't be here forever (5-10 years) to really reap the benefit of the payback. I'll give geothermal a shot when I build my next house.
I've determined I'm going to use an outdoor wood furnace to heat this house. I can get an EPA Phase I certified model for under $7k that is more than twice the recommended size for heating this house (so I can heat my detached garage too!). I won't be smoking out any neighbors and I have an unlimited supply of free split mixed hardwood. It almost seems like a no-brainer for my situation, especially with the 30% (up to $1500) tax credit.
Another plus for the outdoor wood furnace, in my opinion, is the fact that I can do 100% of the installation myself. It's fairly simple for a handy person to be able to install, and I have the advantage that I will be installing the exact model that my parents use for their house, so I can use their setup as a template for installing mine. It does DHW too
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I'm researching insulated PEX though. I'll need roughly 200' to go from the furnace into my basement, and from the furnace into the garage as separate loops. The best way I've heard of people installing the water pipes is to use corrugated drain pipe (without holes) to run each set of lines through to and from the furnace. I'll need a 1" hot and 1" return line for the heat in the house and also for the heat in the garage, and then 3/4" hot and 3/4" return for the DHW. One set of 1" pipes and the 3/4" set of pipes are both going into the house, so they can both be inside one corrugated drain pipe together, and then the other set of 1" pipes can be in their own drain pipe heading from the furnace into the garage. Each pipe needs insulated from each other, however, since significant heat transfer can occur between the hot line and the return line over a 100' (or so) distance. I expect water temperatures to be no more than 200 degrees F in the hot lines. What would be the best way to fit 2 1" lines and 2 3/4" lines (and a 12/3 wire) into a corrugated drain pipe and insulated all 4 pipes from each other? Worst case scenario, I could put the DHW and the house heat lines in separate corrugated pipes in the same trench.