The Sunlighthouse is Austria's first CO2-neutral single-family house with an exceptionally high daylight portion. Two southwestwards oriented roof surfaces entirely equipped with 43 m² monocrystalline photovoltaic panels and 8 m² solar collectors. Together with the geothermal heating pump and direct solar energy output of the windows in 30 years the house will produce more energy than it would have been necessary for constructing, transporting and running the house. As a consequence from this point of time the house will start producing an energy surplus (active house). The project demonstrates that - even in Austria where difficult terrains occur quite frequently - buildings without an „ecological footprint” are possible. (Competition made in collaboration with DI Hein, Photos: Adam Mørk)