I’m finally in the process of adding exterior insulation to my home located in MA (Zone 5A) as part an addition that will include new siding and windows for the entire home.  I’ve been following these kind of retrofits for a while now and I am finally pulling the trigger.  The existing house is 2×4 construction with R-13 batts and and a poly vapor barrier on the interior.  I plan to retrofit the exterior with 2.5″ of Roxul Comfortboard and I have a few questions which I’m sure have been answered here, I just can’t dig up the all the answers.  

1) I plan to replace the windows along with the siding.  For a nailing surface on windows and doors I plan to use 1″ Rigid Foam sandwiched behind 2×4 or 2×6 material laid flat which should give me 2.5″ of thickness to align with the roxul. Should I be using any type of flashing as well?

2) What do I do with exterior lighting fixtures?  How would I mount the metal electrical junction box?

3) What do I used for a metal channel / insect screen at the bottom of the roxul where the siding begins from the bottom?  

4) Does anyone have any fastener recommendations either for hanging the roxul or for the furring strips?  

Thanks!