Worldwide growth and the pursuit of comfort in buildings have led to significant increase in energy consumption, which is considered a current issue. Phase change material (PCM), a thermal energy storage (TES) material, is considered an effective and promising material to reduce energy consumption. In recent years, research on the application of PCM to provide higher comfort for occupants has been growing rapidly. Studies show that it is necessary to consider the optimized phase change temperature of PCMs within the comfort temperature and specific climate conditions. Thus, the objective of this study is to investigate the best optimized PCM under thermal comfort range in the climate conditions of South Korea, and analyze the energy savings of PCMs, using DesignBuilder. The prepared PCMs were n-octadecane (OT), n-heptadecane (HT), and n-hexadecane (HX), which phase change temperatures were close to the thermal comfort range. The results of the circulation water bath test showed that the phase change temperature of the mixed PCMs by OT and HT was (22-23) degrees C, within the thermal comfort range. According to the various mixing ratios of OT to HT, the phase change temperatures of PCMs for OH91, OH73, OH55, OH37, and OH19 appeared at ((24-26), (23-24), (22-23), (21-23), and (20-22)) degrees C, respectively. For energy simulation, gypsum boards with OT, OHs, and HT were prepared, and analyzed by replacing conventional gypsum board of the standard residential construction house model in South Korea. As a result, the maximum energy savings were shown by OH73 in cooling, and OH19 in heating. Consequently, the maximum total energy savings were achieved for OH73, which means that the best optimized PCM for South Korea demonstrated a phase change temperature of (23-24) degrees C. (C) 2018 Elsevier B.V. All rights reserved.