Air conditioning energy consumption in summer represents a challenge in many areas with hot and humid climates. Passive cooling with thermal storage in phase change materials (PCMs) is a very effective way to improve thermal stability of the rooms with light-weight envelope. The main objective of this research is to demonstrate experimentally that it is possible to improve the thermal comfort and reduce the energy consumption of a building without substantial increase in the weight of the construction materials with the inclusion of PCM. This work aims at presenting an overview of the key researches in the field of use of PCMs in buildings and presenting a green approach for their uses in building envelopes with specific implementation on the case of hot humid regions. Thermal behaviour of wall integrated with two different types of PCMS Polyethylene glycol (PEG) E600 and Capric Acid (C10 H20 O 2) was compared by measurements and calculations. Three test cells were built for comparative investigation of the efficiency of passive cooling with the use of the PCMs. This paper deals with the results of experiments carried out in the test cells and possibilities of activation of PCMs for effective passive cooling.