Skippman,

Do you want an open loop or closed loop geothermal system? If closed loop, then do you want wells or trenches?

I ask because the answers to these questions matters in some areas of America.

I think you will get more energy savings by insulating outside of the structural elements (outsulation) instead of between them (insulation). In other words, insulating between 2x6s or 2x8s may not be as effective as board insulation outside of 2x4s. Now if you are wanting to use thicker dimensional lumber for structural reasons, then it may cost much less to go with foam boards outside of 2x4 steel studs with spray foam between the studs.

From the internet:
“Outsulation is the original Continuous Insulation system and is still used throughout the world over masonry and many non-masonry substrates where an air-water resistive barrier is not specified. It is also the system of choice in many retrofit conditions.”

Here is an example of a steel building system that uses outsulation and insulation (NexGen Framing System):
https://www.builderonline.com/building/steel-framing-system-on-the-go_o

I have used various building systems such 2x4, 2x6, Insulated Concrete Forms (ICF), Royal Building Systems (vinyl concrete forms https://andersonpouredwalls.com/page7.html , Structural Concrete Insulated Panels (SCIPs), http://gctm2.com/ , etc.

Ideally, a building system should be resistant to earthquakes, fires, floods, storms, termites, etc. Very few systems will be resistant to all of the perils listed above.

Please contact me by email if you are interested in discussing residential building systems. My email is shown in the signature line below. Use the @ symbol for “at” and “.” for dot.

I have had two houses with Geo and the only reason I did the second is I only need it for AC and hate to see air handlers on the outside of a house.

Geo really doesn't ever perform to specs. I really think to make the system to meet manufactures spec the field size and cost is to high and/or they don't calculate in the field pumping costs when they do their efficiency calculations.

My current house has both natural gas and geo heating. I have run the house on both and the natural gas is 80% the cost of the geo to run and heat the house.

Mini Splits are an all-in-one unit so the specs are what you are going to get. Anything 20 seer and above is better then natural gas for efficiency.

I am in Michigan but I am guessing cooling dominated areas are similar but on the cooling side. Goo luck.

Is your geothermal system well or trench based? Do you know what the water table was like in the areas you had them dug? I'm just curious if it's a matter of the geology of the area, or an inherent failure of the geothermal system. Did you use your geothermal to heat any of your water or was it purely for HVAC?

I'm considering the mini-split option but that will require external condensers and I'm fighting against muggy hot weather so I don't know how efficient that can be.

As for the structure itself and it's overall insulation I've been trying to do as much research as I can. Here was my wall plan keeping in mind I am not an architect or a contractor.

From outside in:
1.) James Hardi HL10 Zoned Exterior siding (likely Hardi Plank)
2.) Zip Systems insulated R-Sheathing (Fully sealed and flash taped)
3.) 2x6 (potentially treated) wall studs with spayed open celled foam.
4.) Drywall

My first house had 5000 feet of pipe in the ground with 3 loops 6 foot deep and 2 loops to a pond.

Current house is well based.

I am just saying that if you go Geo make sure you get something in writing for payback and performance.