The control of energy in the industrial sector and the reduction of consumption in the building sector will be key elements in the energy transition. In order to achieve these objectives it is necessary to use materials with energy performance adapted to their use as well as insulators or super-insulators. In both cases, a thorough knowledge of their thermal properties will be required for optimal success. This revised and updated 2nd edition enables the reader to choose the measurement method best suited to the material they are characterizing and provides all of the information required in order to implement it with maximum precision. This work is intended to be accessible to anyone who needs to measure the thermal properties of a material, whether or not they are a thermal engineer.