In Japan, residential and commercial buildings constitute 30% of the total energy consumption. Since the oil crisis in 1973, many countermeasures for energy saving have been adopted but energy consumption still increases every year. The mean increase ratio for the last 20 years is 3%. After the Kyoto Protocol was confirmed in February 2005, the Japanese government published "The Program for Accomplishing the Target by the Kyoto Protocol" and various energy saving strategies have been implemented. On the other hand, in China, as a result of rapid economic growth and improved living standard, energy consumption is also escalating. Due to the huge population of China, increased in energy consumption is expected to impact significantly upon global warming. This paper presents the trends of CO2 emissions in Japan and China, followed by the actual situations of energy use, indoor environment and energy saving strategies in Japan. In this investigation, the statuses of energy use, indoor environment and energy saving policies in China were elaborated.