A method of manufacturing flexible insulated duct includes wrapping a substantially flexible tubular core with a layer of insulation. A substantially flexible outer layer is wrapped about the layer of insulation such that longitudinal edges of the outer layer circumferentially overlap to define a longitudinally extending seam. The overlapping longitudinal edges of longitudinally extending seam in the outer layer are bonded together, thereby forming the flexible insulated duct. The flexible insulated duct is then cut to a discrete length and installed at a job site.