Eureka!

While thinking about the Bohlenwand technique I got inspired. And I think I have come up with a system that could work well for a modern house and be suitable for modern ideas of comfort.

In Europe the modern twist on Bohlenwand is to use special manufactured panels that are made of foam sandwiched between layers of wood. This is a good system and works well, but the only problem is we can't get those panels here.

So I thought of an idea. Instead of 1 single panel sandwich, what if there were 2 completely separate layers of wood each in its own key in the posts, and the insulation (preferably foam of some sort) is placed between these layers. It would look something like this:

or a plan for a plan drawing that makes the various aspects a bit clearer maybe:

This system, I think, has the potential to work better than the European version. The reason is that It can be tightly sealed quite easily.
The outer layer of boards should be the first to be put in. They would be standard 1x stock set back from the outside edge perhaps 3/4". It should be noted here that this is designed to be used in a close posted system, 3/4" boards are plenty stable over 3 or 4 feet but over 12' or more they would be far too wobbly and would require studding.
These boards would be plastered over on the outside with clay and lime to make the infilled panels flush with the outside of the timbers. On the inside spray foam would be used to seal off all of the joints from drafts.
The inner layer could also be 3/4 boards, but I think that thicker boards would work better. The reason is that it would allow you to take advantage of wood's thermal mass on the inside of the structure where it is the most beneficial. I have shown here 2x stock set back 3/4 inch from the inside face of the timbers. This would allow a little bit of timber exposure. Keep in mind though that any setback from the inside reduces the size of the insulation cavity, but a certain amount of setback is required so that the boards can have a channel to key into the posts.
The inside can use nice boards for an all wood finish, or you could use cheaper wood and coat with plaster.
The insulation layer can be just about anything; it could be cellulose, spray foam, foam board, straw, wool, shredded tires, or whatever you could dream up. You have a very large cavity surrounded on 4 sides by solid wood.
Part of the beauty here is that this system can easily take advantage of both thermal insulation and thermal mass. It can be easily adapted to different climates simply by changing the infill material and the width of the inside boards.
Obviously this is not going to be a super insulated house, but it's not designed to be. However, it could be with 1 minor variation. eliminate the outside layer of boards and replace it with foam sheathing nailed or screwed directly to the posts on the oustside (you may want a layer of wood or plywood for rigidity). This of course would not give you a half-timbered exterior however.

Now this is kind of a side track from my original question, which still stands. That question being whether or not a traditional infill system would be suitable for a shop building in Indiana's wet, stormy climate. My current line of thought is that clay based infills would be too susceptible to wind-driven moisture and high humidity, but that a Bohlenwand style wall with thoroughly sealed joints might do the trick.

As a side note, The use of clay on the exterior of the Bohlenwand seems like a very good idea to me, provided it is sealed by the plaster. This is because a silt-clay loam is highly hygroscopic (unlike pure clay) but does not retain high levels of moisture (unlike pure silt). This means it draws water more readily than the wood will, so it effectively keep the wood dry under normal conditions, and it at the same time will readily diffuse the water into the atmosphere after the moisture event has passed.