Hello, I am at a decision point on roof insulation. My options are as follows 1. Vented roof asemby w/2″ of rigid board for a baffle, trusses furred out to accomodate R-30 of fluffy insulation for a total R-value of 40 However between the knee wall and top chord I would use all rigid board to limit the reduction in head height. Could I add rigid board as a last layer to add R-Value, & reduce thermal bridging to this whole assembly without causing moisture issues? If so what type would be best suited (faced, unfaced, etc). 2. Non Vented Flash & Batt w/3″ cc spf and 8″ of fluffy insulation (blown in sheeps wool @R 4.3 per inch), smart vapor barrier. I am worried that air sealing around my trusses will prove challenging. 3. Exterior continuous insulation – It is possible to remove my roofing (metal), install rigid insulation 3″ and reinstall the roof. The roof sits on horizontal 2×4’s 2′ apart. I could pull those up lay the rigid foam and reinstall on top (not ideal) or insulate around them, but those areas would have reduced insulation. Would that pose a problem? Also, I am unsure whether i could properly detail this type of assembly. The truss is designed with a bonus room *zone 4a zip 37370 Thanks in advance.