I live in an early Lindell cedar kit home. I shan't go into the construction method but it is far from conventional. I need to add insulation and also re- roof. I was thinking of stripping the roofing and sheathing, laying down either 2x4 or 2x6 rafters, filling the bays with Thermax insulation, sheathing and re-roofing. My question is if the rafter bay is not completely filled do I absolutely have to vent the bays. I understand that the reflective coating of the Thermax is only effective when used with an air gap, but to vent the roof, because of the original construction method, would be a total pain in the behind. Any and all ideas will be greatly appreciated.