Many eco-friendly buildings have been constructed as one of the measures for preventing global warming. In these buildings, various elemental technologies have been installed and expected to perform their functions effectively in long-term operation. For this purpose, the maintenance conditions for these technologies are an important factor. In this study, we investigated the actual conditions and obstacles in the elemental technologies via a questionnaire and hearing survey and showed that the maintenance conditions influence the functional obstacles greatly. Next, we investigated the quantity of rainwater used in rainwater use systems and considered the relation between its utilization and its maintenance conditions in detail.