One minor point - you have used the term 'waddle and daub' several times now. It's not waddle, my friend, its wattle. Waddle is, to quote straight from the dictionary:

1 : to walk with short steps swinging the forepart of the body from side to side

2 : to move clumsily in a manner suggesting a waddle


Wattle, on the other hand, which was the word I believe you were intending, comes from the Middle English wattel, from Old English watel; akin to Old High German wadal: lit. "bandage"

Dating from before 12th century, the word wattle means:

1 a : a fabrication of poles interwoven with slender branches, withes, or reeds and used especially formerly in building

b : material for such construction

c (plural) : poles laid on a roof to support thatch

Hazel switches were a common choice, as far as I know, for wattle in English timber construction.

Please forgive my pedantic language policing, however I am wary of the fact that once that a few people start confusing 'waddle' for 'wattle' in short order everyone will be making the same mistake.

As for your wall system, I'm absolutely with you on the dislike of SIPS. However your system, it seems to me, uses an excess of material to accomplish the structural requirements, given the 2x6 infill studs, and the posts and plates are a major thermal bridge in the wall system you are describing.

Since the wall can be framed entirely with 2x6's and be plenty strong enough to carry the roof, and the timber posts present that thermal bridge, and are only visible on the interior as an inch or three projection, then it seems to me that the timber posts are pretty much superfluous in your system and could be replaced by, dare I say it: trim pieces.

Now, that's not what I would suggest you do, however if you are going to argue for a structural timber frame, then any infill system should be more about providing insulation than about providing structural support - to accomplish that you might consider eliminating the 2x6's and go to some sort of 2x2/2x3 double wall type of infill system, as has been suggested above.

Also, with 9" posts and plates that overhang the posts by 3" or so, as you mentioned above, you end up with pretty massive plates. While I'm not clear on exactly what you are envisioning, if the plate is to be 12" wide then presumably it is at least 8" high? Or are you envisioning a 12x12 plate? That sort of timber is likely to be coming from a halved log at best. or be boxed heart, which will mean that the grain orientation (using green material as you imply) of those sticks will make them prone to cupping across their width, and likely checking pronouncedly as they dry. Such plates would be yet another significant thermal bridge in such a wall system, not to mention a source of air infiltration as they shrink and cup.

Such plates seem, to me at least, a wasteful use of the resource, given that they are excessively large for the structural function of 'wall plate' in a residential application. Wasteful, i.e., 'not economical'.

Since a 2x6 wall by itself would give you that 5.5" cavity for insulation, and would employ dry material with minimal thermal bridging, seems to me the most economical option in comparison to your other plan. All the timber wall elements would add nothing essential in terms of structure, and simply add cost (in terms of labor, materials, and thermal performance losses) - they must be there, it would seem that they do little else than show a few inches of themselves to the interior. Using a 9" thick wall post that is structurally redundant, lowers thermal performance and only reveals 2~3" inside the building seems unwise.

It's good that you are thinking of alternative systems and are considering lots of options and that you are open to critical feedback here on this forum.