CO2 reduction is the most urgent issue the world is facing. So, there should be a measure to reduce the CO2 emission in construction industry which has more released CO2 gas than other industries. CO2 emission of building depend on using energy. Then efficient energy use process working efficiently at CO2 reduction. Therefore In this study, author find the technical possibility of saving the building energy using the PCM which is able to control heat, storage heat and potential heat. So, it considered that apply to floor heating type which is major heating system of living space in Korea. And evaluate the Using possibility.