**Abstract**

This chapter deals with the investigation of the effect of a PCM wall on building indoor thermal comfort. To achieve this objective, an experimental framework was installed in the laboratory of thermal processes in Borj Cedria, Tunisia, which is essentially composed of a test cell having the dimension (0.5, 0.5, 0.5 m<sup>3</sup> ) conceived with a new structure of wallboards. One of the sides of the test cell is a cavity filled with PCM-27, which represents the PCM wall. A numerical investigation by using specific FORTRAN program was also achieved to solve the energy and the exergy mathematic relations to evaluate the PCM wall performances. TRNSYS simulation program was also achieved to simulate the behavior of the integration of the PCM wall in a typical modern house according to Tunisian scenario. It is found that during the hottest period of the day, the temperature of the tested room with PCM wall achieves 25°C, while that without PCM wall exceeds 27°C. During the night, the temperature of the tested room, with PCM wall, decreases in the value of 20°C. It was also found that during the night, the kid's room with PCM wall is reduced by 8°C.

**Keywords:** PCM wall, building, thermal storage, FORTRAN, TRNSYS
