is thermal conductivity independent of thickness
Insulation works by reducing the transfer of heat by means of a barrier. Unfortunately in most cases the better the insulation the more it costs, so like most things a balancing act is required. To understand insulation you need to know what thermal conductivity, R values and U values are. Thermal conductivity is the measure of how easily heat flows through a specific type of material, regardless of the thickness of the material. The lower the thermal conductivity of a material, the better the thermal performance (i.e. the slower heat will move across a material). See below for some example materials and there conductivity values.