A thermal process device for heat treating a product or plurality of products, the device comprising: a thermal processing chamber having opposed distal ends (18, 20) and at least one controllable heating zone; at least one buffer zone disposed at each of the distal ends (18, 20), the buffer zones and at least one heating zone of the thermal processing chamber forming a heating element assembly having an inner and outer surface; and at least one layer of insulating material (28, 34) disposed along the at least one buffer and heating zones of the thermal processing chamber and forming part of the heating element assembly, the at least one layer of insulating material (28, 34) has a controlled efficiency being applied non-uniformly across an axial length of the heating element assembly; and wherein non-uniformly means one or more layers of material having the same or with different grades of thermal conductivity, the one or more layers having the same or different thicknesses, a layer having different thicknesses or different grades of thermal conductivity varying along its length, a layer or layers having different materials with different grades of thermal conductivity side-by-side along its length, the different portions having the same or different thicknesses, by using insulating material with different grades of thermal conductivity, by using differing arrangements of multiple layers of the insulating material, and a combination of all the above; and wherein controlled efficiency means the efficiency of the insulation is controlled by varying the thickness, thermal conductivity grade of the insulation or differing arrangements of multiple layers of the insulating material in any combination; and wherein a portion of the at least one layer of insulating material (28, 34) located at the at least one buffer zone has an higher efficiency and a portion of the at least one layer of insulating material (28, 34) at the heating zones has a lower efficiency compared to the portion of the at least one layer of insulating material (28, 34) located at the at least one buffer zone. a thermal processing chamber having opposed distal ends (18, 20) and at least one controllable heating zone; at least one buffer zone disposed at each of the distal ends (18, 20), the buffer zones and at least one heating zone of the thermal processing chamber forming a heating element assembly having an inner and outer surface; and at least one layer of insulating material (28, 34) disposed along the at least one buffer and heating zones of the thermal processing chamber and forming part of the heating element assembly, the at least one layer of insulating material (28, 34) has a controlled efficiency being applied non-uniformly across an axial length of the heating element assembly; and wherein non-uniformly means one or more layers of material having the same or with different grades of thermal conductivity, the one or more layers having the same or different thicknesses, a layer having different thicknesses or different grades of thermal conductivity varying along its length, a layer or layers having different materials with different grades of thermal conductivity side-by-side along its length, the different portions having the same or different thicknesses, by using insulating material with different grades of thermal conductivity, by using differing arrangements of multiple layers of the insulating material, and a combination of all the above; and wherein controlled efficiency means the efficiency of the insulation is controlled by varying the thickness, thermal conductivity grade of the insulation or differing arrangements of multiple layers of the insulating material in any combination; and wherein a portion of the at least one layer of insulating material (28, 34) located at the at least one buffer zone has an higher efficiency and a portion of the at least one layer of insulating material (28, 34) at the heating zones has a lower efficiency compared to the portion of the at least one layer of insulating material (28, 34) located at the at least one buffer zone.