Hello, I'm considering re-insulating my 1-1/2 story 1932 house in central Iowa. Currently, it has plaster-lath 2/4 walls, blown cellulose insulation, 15 lb. tar paper, 1 inch polyiso r-board insulation, typar wrap, and vinyl siding. I'm thinking about the following: remove siding, cut 1-1/2 inch out of polyiso at the studs over the wood sheating, fur out with 1-1/2 x 2inch, put 1 inch polyiso over original polyiso between the furred out studs, install another layer polyiso over the furred out studs, 15 lb. tar paper, and then space out the vinyl siding for ventilation. This would make 3 inches of rigid insulation. I'm concerned about condensation in the walls, and also the water drain plane. I did not tape the 1st layer of r-board. My thoughts were to allow any moisture that got in the walls to get out. Also, I furred out my windows and doors. Is there an easier way to install more insulation on the exterior, or a different method? Thanks