The integration of a PCM layer into an external building wall diminished the amplitude of the instantaneous heat flux through the wall. The types of PCM, its location in the wall and its amount, have been studied in this paper. A two-dimensional transient heat transfer model has been developed and solved numerically using the commercial Computational Fluid Dynamics (CFD) package Fluent. The numerical results have been verified and validated with an experimental model. The considered model consists of usual brick with square holes used as construction materials for residential buildings in Algeria, some of these square holes are filled with PCM. The results showed that the PCM introduced in square holes can improves considerably the thermal inertia of brick and a combination of the types of m PCM, its location in the wall and its amount, is very important for improve reduction of heat gain before it reaches the indoor space.