The cost of energy use in buildings around the world is gradually increasing. To achieve energy saving in buildings, among the Thermal Energy Storage (TES) systems available, the use of Latent Heat Storage (LHS) is being actively studied. To effectively use an LHS system, Phase Change Materials (PCMs) are applied to buildings, and thus Shape-Stabilization PCMs (SSPCMs) must also be used. In this study, SSPCMs were manufactured using a large-capacity vacuum impregnation machine, and consisted of Exfoliated graphite nanoplatelets (xGnP) and n-octadecane. The SSPCMs were divided according to size (A, B, C, and D). SSPCMs were applied to a gypsum board (GB). Through a compressive strength test, a weight of 5% was applied to GB_A5, and the strength was reduced by 23.1% compared to GB and 50.1% for GB_A10. The thermal properties were analyzed based on a dynamic thermo-graphic analysis and dynamic heat flow analysis. From both analyses, it was confirmed that the GB with SSPCM showed a sufficient latent heat range and a corresponding exothermic range, compared to the reference GB. Based on EnergyPlus 8.5., a cooling energy reduction of approximately 3.4% was achieved through the addition of 10% SSPCMs to GB under the operating conditions. Therefore, it was proven that the application of SSPCMs to building materials is reasonable for achieving energy saving in buildings.