Carina Storrs in Scientific American:

Werner-sobek-triple-zero-building(1) Overlooking the city of Stuttgart in southern Germany, a four-story modern glass house stands like a beacon of environmental sustainability. Built in 2000, it was the first in a series of buildings that are “triple-zero,” a concept developed by German architect and engineer Werner Sobek, which signifies that the building is energy self-sufficient (zero energy consumed), produces zero emissions, and is made entirely of recyclable materials (zero waste).

Since the construction of the first triple-zero home, Werner Sobek's firm of engineers and architects, based in Stuttgart, has designed and built five more in Germany, with a seventh planned in France. The energy used by these buildings, including the four-story tower where Sobek resides, comes from solar cells and geothermal heating.

More here.