Abstract: An improved heat insulating jacket slit lengthwise thereof held closed by a unique pair of dissimilar separable snap-lock seam members formed of extruded plastic and designed for heat-fused assembly to the inner plastic layer of flexible laminated sheeting having an outer layer nonfusible to said seam members. Each seam member includes a narrow groove sized to snugly seat and conceal the adjacent lateral edge of the sheeting. Each seam member includes internesting snap-lock members positioned to interlock when laminated sheeting fused thereto is wrapped about ducting. A blanket of resilient heat insulating material is laminated to the inner plastic layer of the sheeting and aids in holding the seam members interlocked.

Abstract: Enclosed is an improved snap-on heat insulating jacket for ducting and method uniquely designed for simplicity and ease of assembly. Resilient heat insulating material is laminated to a flexible sheet plastic main body provided with interlocking snap-on seam members positioned, when closed, for concealment by an external guard flap coated on its inwardly facing surface with pressure sensitive adhesive thereby to embrace the ducting with a cover having a substantially continuous smooth outer surface free of foreign matter collecting crevices and the like.