Self-regulating heater cable with buffer layer

A self-regulating heater cable assembly, the assembly comprising:

• first and second power supply wires configured to carry electrical power and separated by a solid electrically insulating spacer;
• a self-regulating heating element in electrical contact with the first and second power supply wires and converting electric current into thermal energy when the first and second power supply wires are energized, the heating element being spirally wound around the first and second supply wires and the spacer, and having a spacing that creates gaps between consecutive windings of the heating element;
• a conductive ground layer that couples the heater cable to electric ground, the ground layer surrounding and physically separated from the heating element and the first and second supply wires;
• an outer jacket surrounding the ground layer;
• and
• an electrically-insulating buffer layer disposed between the ground layer and the heating element and in thermal contact with the heating element, the buffer layer being extruded over the heating element to result in filling of the gaps between the windings of the heating element, the buffer layer comprising a polymeric material and having a thermal conductivity greater than air at standard temperature and pressure, and the buffer layer being porous and incorporating at least one of voids and pockets containing trapped gasses.