Recently, many studies have been carried out on the reduction of energy consumption. Therefore, we prepared PCM/silica fume composites for the reduction of energy, by improving thermal efficiency through latent heat storage. We manufactured these samples to apply to a building material, such as concrete. PCM/silica fume composites designed to produce high thermal performance were prepared through vacuum impregnation. Impregnation of PCM is one way to prevent leakage of liquid state PCM, and vacuum treatment is effective in conserving the thermal properties of pure PCM. We carried out experiments to confirm the characteristics of the PCM/silica fume composites, using SEM, FTIR, DSC and TGA analyses. SEM analysis showed that each PCM was completely incorporated into the pores of the silica fume. The peaks of pure PCM and silica fume are still shown in the PCM/silica fume composites peaks from the TGA analysis, because PCM/silica fume composites are composed of mechanical bonding between the pure PCMs and the silica fume. From the latent heat storage analysis, we confirmed that the PCM/silica fume composites have high latent heat storages, since each PCM was well incorporated into the structure of silica. Also, we found that the high thermally durable properties of silica fume led to an enhancement of the thermal durability of the PCM/silica fume composites. Consequently, we expect the PCM/silica fume composites to be useful for applying to building materials, such as concrete, due to the shape stability characteristics and high thermal performance of PCM/silica fume composite. In future research, this experiment needs to be expanded, in order to obtain high heat storage properties and thermal durability.