The government aims a realization of Zero-energy-house till 2030. There are many existing houses where we should live for a long time in Japan. We have to think about a solution for the renovation intended to realize the Zero-energy in existing houses. In this research, two existing houses were renovated. One is a two-family house, and the other is a house for seniors. By monitoring them, it was found that we can save energy up to a certain degree. However, there are some problems to realize the Zero-energy, especially in this case.
