Research so far …. [don’t forget this is only on the inside of the outside wall.]
The closest manufacturers for specialty insulations that would fit this new wall-on-wall version are in Kentucky and Canada and wherever Roxul is made. They all make some version of a semi-rigid batt, and all are about 3.5 inches thick. That would mean … correct me if I’m wrong … that the new wall-on-wall framing would have to be a 2 x 4 with the long screw going through a drilled hole in the 2 inch part of the board. Boards would also be laid the length of the ceiling and the floor – a complete set of studs/joists on top of the existing wall.
BUT! What’s to say that you couldn’t put in “standard” insulation instead of the thermal board the video shows, right? Hmm. Still researching. I wonder …