A helically formed flexible duct primarily directed to applications in ducted heating, ventilating and air conditioning, of three dimensions including a predetermined length, an inner diameter reinforced with a helically laminated wire member between self laminating substrate, an outwardly radial compartment formation constructed with strip portions of substrate material which form gaps to accommodate outwardly expanding radial dimensions and containing an insulating member, and an outer covering member delivered to a larger radial circumference at an applied circumferential speed exceeding the circumferential speed of the inner diameter substrate tube formation rate.