Am currently in the middle of a major remodel on a late 1800’s farmhouse in Eastern Washington State. Have discovered a ‘insulation system’ I’ve never seen and maybe someone out there has. I am unsure of how to ‘add’ to it. The wall consists of typical roughcut stud 3 1/2” thick with 1×8 shiplap on each side. After the outer shiplap, there is a thin 1” batt. In its encasement is a thin white cotton like substance. Then there is a couple inches or so of air space followed by a very waxy, tough looking paper. Its color of greenish brown. Then the inner shiplap and cheesecloth and typical wallpaper. My question is how do I insulate this wall in regards to moisture?? Do I build an inner 2x wall and insulate with fiberglass batts? Or do I use ridgid foam of some sort on the out side when I install new siding and windows? Any advice on this would be greatly appreciated ! Thank you!
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