I am replacing my conventionally-framed roof with timber frame trusses, covered by 6 1/2" urethane core SIP's. In order to achieve equivalent insulation value in the 2x4 framed walls, I have decided to apply rigid insulation. My questions are: Should I go with 1" or 2" thick sheets? Should they be applied to the inside or outside of the walls? Anything else I should be thinking about? I live in New Jersey, energy zone 5. Thanks for your help.