Burying ducts with insulation board

In Climate zone 1A would it be acceptable to create R13 around flexible R6 ductwork by boxing around flexible ductwork with equivalent of R13 insulation board ( 1″ Sika R… In Climate zone 1A would it be acceptable to create R13 around flexible R6 ductwork by boxing around flexible ductwork with equivalent of R13 insulation board ( 1″ Sika R…Read MoreGreenBuildingAdvisor