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 metha- crylate (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.