Microcapsules with a high amount of PRS paraffin wax encapsulated and narrow size distribution were prepared by a Shirasu porous glass (SPG) emulsification technique and a Subsequent suspensionlike polymerization process. An experimental design approach, based on a central composite design, was used to determine quantitatively the effect of RepSol-YPF Paraffin (PRS) paraffin wax/styrene mass ratio (PRS/St), percentage of polyvinylpyrrolidone/styrene mass ratio (% PVP/St), and water/styrene mass ratio (H2O/St) on the phase change material (PCM) microcapsules properties. The % PVP/St mass ratio was the most important parameter affecting the particle size distribution. The thermal energy storage of microcapsules increases with the PRS/ St mass ratio used. The following synthesis conditions, mass ratios PRS/St of 1.02, % PVP/St of 9.43, and H2O/St of 8.23, allowed the the proper main particle size in number (4.80 mu m) for fabrics applications containing the maximum phase change material encapsulated with a latent heat of 102.42 J/g to be achieved.