An insulated HVAC duct component such as a transition box includes a first insulation layer and a second, different insulation layer. The transition box includes at least four sidewalls and one of a top and a back wall, the transition box further including a first access port and a second access port, the first access port having a different cross section than the second access port, one of the access ports being spaced from a nearest sidewall by less than 2 inches. The first insulation layer is located along an inside surface of the box. The second different insulation layer overlies the first insulation layer, the second different insulation layer having an air impervious surface, wherein the combined thickness of the first insulation layer and the second different insulation layer is less than 2 inches.