In this paper, the phase change material (PCM) to increase the heat capacity of buildings is applied to building materials. The building materials use not only sensible heat but also latent heat so that the building materials are useful to maintain the pleasant indoor environment and to save the building energy. The purpose of this paper is to reduce the greenhouse gases due to building use. The model experimental research results are as follows. (1) The test shows that the sheet or pipe type heat storage materials are effective to reduce the daily temperature range, rather than the standard type. (2) The sheet type material has better capacity than the pipe type material to delay the increase in indoor temperature. (3) The building material mixing the phase change material can be useful to maintain indoor comfortably.