I am following the thread with curiosity & interest* - thank you for the great project presentation.
But I have a question: probably I missed or overlooked it somewhere, but what wall construction did you finally choose and how did you solve the insulation? At some point you - if I remember correctly - wrote about wavering between prefabricated walls and in-situ concrete, or that they should no longer be core-insulated due to problems with installing the window elements.
I am also pondering in my (much smaller) residential basement construction whether we should go towards prefabricated walls with core insulation, or exactly what kind of perimeter insulation we should take.
*And yes, a little bit of envy too…