The Phase Change Materials (PCM) are materials which absorb a great quantity of energy during the change of phase solid /liquid and relies it during solidification An application of these materials is thermal energy storage. The PCM integrated into materials of the building can reinforce their inertia and reduce the power necessary for the heating and air conditioning. This is particularly true for the buildings of the tertiary sector whose envelope is light. Nevertheless, one of the characteristics which limits the use of the PCM is their low conductivity. The objective of this article is to propose a selection of materials having a conductivity high enough to make it possible to ensure an air conditioning in summer while limiting, even while removing, the use of energy (electricity or fuel) thanks to walls containing these PCMs. This article consists of two parts: - The first part exposes the problems of the study and specifies the context in which the use of a PCM as a passive air conditioning system fits. - The second part fixes the selection criteria which will allow, in a first approach to choose certain materials.