I think I'm on the right track; but, want to double check with you folks who are doing more commercial work. 2009 IECC; 503.2.7 " All supply and return air ducts and plenums shall be insulated with a minimum of R-5 insulation when located in unconditioned spaces and a minimum of R-8 insulation when outside the building." I've only seen R-6 being used inside the building. So all ducts within the building could be a minimum of R-5? I know it's a silly question, but have been doing very little commerical for some time now. Thanks, Uncle Bob