Organic paraffinic PCMs called Micronals DS 5038X in powder form (from BASF) are considered in this study. They are composed of a mixture of paraffin waxes with a melting point of 25 1C and a phase change enthalpy of 100 kJ/kg according to the manufacturer. The paraffin is microencapsulated in a plastic layer of polymethyl methacrylate (PMMA). The microencapsulation technique is used to facilitate the incorporation of the phase change material into the construction material and to prevent the paraffin leakage during the PCMs melting.