Rate my knee wall insulation plan
I want to re-insulate the upper floor of my 1920 1.5 story.
Here are pics showing current configuring and my planned new configuration.
My main questions are:
1. On the short exterior walls, is it weird that the shiplap and weather barrier are installed on the inside face of the studs, which prevents me from accessing those stud bays to add insulation? Is my proposal to create a small 2×6 wall immediately inside this exterior wall a reasonable one? Should there be some sort of channel and air barrier between the insulation and the shiplap?
2. I have seen it suggested that such an exterior wall would be designed to dry to the inside, and to not put a interior vapour barrier. Is that because the rigid foam use to create the air channel is not vapour permeable? What if I use some kind of vapour permeable fibre board to create the air channel instead? Could I then install rigid foam/vapour barrier on the interior have the wall dry to the outside as planned?
2. Should I be adding vapour barrier to the flat part of the ceiling between drywall and joists, taped to the rigid foam on the sloped parts?