I'm trying to figure out the best way to insulate a basement wall that is partially underground in the deep south (humid with clay soil).
To avoid moisture build-up, the part I feel like I've got is to cover the cinder block with unfaced polystyrene, then 2x4 or 2x3 framing filled with unfaced insulation (so that when moisture gets in the walls from the soil, it can slowly migrate to inside the basement rather than sit in the walls and grow mold).
But what I'm not sure about is at the rim joist. It's easy enough where a rim joist sits on top of the 2x4 lying on the top of the cinder block. But the walls that are perpendicular to the floor joists do not have rim joists sitting on the 2x4 on cinder block. Instead, the rim joist sits on the brick venier (brick covers basement walls, then transistions to vinyl siding at the main level) with floor joists sitting on the 2x4 lying on top of the cinder block (I've included a sketch to show something of a cross section).
So what do I do to slow the migration of moisture in the air pocket between the brick and cinder block, that is currently open to the basement.