A simple, wooden cubic structure with a flat monopitch roof located about 5 km to the south of Winterthur in the motorway service area Kemptthal: these are the headquarters of Marché International. The construction was designed with a focus on energy efficiency, sustainability and ecological balance, as well as offering high quality and healthy workplaces. As the first zero-energy office building in Switzerland, the construction has been certified by Minergie-P Eco, currently Switzerland’s most stringent standard, which the building even surpasses. Significant design elements include a fully glazed southern façade, a highly insulated and carefully sealed building envelope and a monopitch roof with an inclination of 12° to the south. Complete coverage of the roof with thin-film PV cells allows it to fulfil its additional power-generating function. A life cycle analysis has shown that the energy consumed by the new construction in the course of its entire life cycle is about one third of the energy required by a standard Swiss building.