Structural connections are the hardest parts to design for thermal bridge-free construction. I've decided to install insulation under my strip footings. There are high-strength insulation products such as Foamglas and Pur-knit and others. They are expensive, and Foamglas is friable (brittle). Therefore I plan to use HI-load 60. An XPS 60-psi compressive strength rated insulation under the strip footings. This stuff is R-5 per inch. For nearly twice the price, you can buy HI-load 100, and Foamglass is beyond that price. As an added benefit, the HI-60 comes in thickness up to 3".
The DOW building solutions rep said footings are insulated routinely by a large production builder in the Ottawa area - they have clay/silt soils that are highly prone to frost heave, and the builders insulate under the footings to protect their foundations during construction. Railway tracks are also insulated using these HI-load insulations.
More on this later.
In Europe, they are making Foamglas gravel - all with recycled glass - I think this is fantastic, but no luck getting it here.