Green architecture advocates for sustainable energy sources, including the safety and reuse of building materials and updating existing buildings with efficient technology. The focus of green architecture is to effectively reduce the adverse effects of many structures on their surrounding environment, such as air pollution. Common green architecture elements include solar panels, rainwater harvesting, commercial composting toilets, green roofs, and energy-efficient windows. In addition to being healthy for the environment, green buildings offer benefits for the occupants, such as improved air quality. Any architecture firm wanting to add green architecture to their list of services must undergo additional training to provide these services for their clients successfully.