From the article:
The home’s butterfly roof works in conjunction with the Night Sky system, capturing, collecting and directing the system’s water to an insulated storage tank. Water lost through evaporation is made up for by the roof’s capture of rainfall. On an annual basis the home is anticipated to generate a water surplus based on rainfall capture and reuse as well as graywater capture and reuse, thus not adding to ongoing water supply stress in the state.
See the full story here.