Abstract: A collar-like device for reducing lateral heat dissipation from range top heating elements during cooking operations. An integrally-formed annular collar means of generally frusto-conical configuration is adapted to rest atop a range, in surrounding relation to a heating element disposed on said range top. A generally toroidally-shaped pocket of heated air surrounds an item of cookware adjacent its lower portion when such cookware is slideably received within the opening of the collar-like device surrounding the element.A first alternative embodiment has a hollow collar so that a dead air space interiorly of the collar-like device provides an additional thermal barrier.A second alternative embodiment provides a plurality of successively smaller nesting collars to accommodate cookware of differing sizes.