  
Zone: 4A (North GA)

  
  
I have 3 (knee?) walls in my unconditioned vented attic that face my living room. They are currently insulated with fiberglass batts with paper facing the sheetrock of my living space. I'm looking to improve the R value of these walls. The living room is the warmest point in the house during the summer and the walls facing the attic measure 8-10 degrees warmer than all other walls/ceilings. The attic floor/ceiling only has about 5-6" of blown in insulation (not sure if cellulose or fiberglass), and when I check the temp of the ceiling, its closer to ambient room temperature, so my assumption is the knee wall fiberglass batts aren't doing a very good job of insulating.



I plan on fixing the fiberglass batts to reduce air gaps or most likely replace them with rockwool. It seems poorly secured. Then over top of that, I was going to put foam board and seal it with spray foam around the edges. However, I'm reading this could sometimes be a bad idea and referred to as a vapor barrier sandwich but I'm not sure how big a deal is with this use-case sinceI have seen this also recommended to do. I also saw someone recommending rockwool comfortboard instead of foam board and not worry about spray foaming anything to let it breath. I'm just trying to do this right but I'm getting some mixed information. 



Attic is ventilated with soffit/ridge vents - in my diagram you can see 1 of the 3 knee wall sections doesn't' have vents directly in that space, but there are vents on both the north and south sides of it. I included this as I'm not sure if this is a huge deal or not.



The studs are 2x4s except for 3 or 4 of them that I found are actually laying flat instead for whatever reason. I will probably put 1.5" foam board in these sections.



Any insight is much appreciated.   


Half Vaulted Ceiling - Knee Wall Insulation