Foamboard over cedar
I will be starting a fiber cement and new window install soon had questions regarding the install. My current walls are 2x4s with rockwool bats followed by a 3/4″ fiberboard with felt like facing on the exterior side (thinking its celotex or similar) followed by cedar lap siding. My original plan was to remove the cedar lap, leave the fiberboard, cover with 1″ foamular tounge and groove, tape seams, followed by tyvek. The replacement windows will be new construction so was going to install the windows over the tyvek/foam with a piece of 5/4 cedar under tyvek used under the window for additional support. This all would ve followed by furring on 16s and cement board over it. Now I am considering leaving the current cedar in place, placing foamboard over it and using spray foam to fill the gaps at edges to seal the space between the foam and original siding. I feel this will save a lot of time, some money and be less disruptive. Cedar siding is in good shape and where i have pulled a lap to check, it looks good. Looking for thoughts on doing it this way and if its not a good idea, how does theoriginal plan sound? Im Illinois, zone 5. Thanks!