I’ve discovered the source of substantial air leakage in my wall framing and I’m trying to determine the best way forward. I’m not sure how to correctly describe this construction so I’ve attached some pictures but I have horizontal beams making up all four sides of the house and 45 degree beams pitching the vaulted ceilings. Those two beams are joined with lag bolts at the sides.

While doing some repairs, I popped off a fascia board on the outside, revealing the backside of the beams. There’s absolutely zero air sealing and they leak straight in to the building envelope. The fascia boards were attached with two nails on either end and some fiberglass batts stuffed behind them, grey from filtering all of the inbound air for however many years. You can see the spray foam I’d try to hit from the inside at some point.

The way I see it is that these are very similar to rim joist cavities. I could fill with some kind board, spray foamed around the edges or I can have the company coming to hit my floor joists with closed cell spray foam hit these at the same time.

Am I correct in thinking that air sealing is the primary goal here and the R value on these beams is going to be fairly negligible? Should I prefer one option over the other?