The Gründerzeithaus in the inner city of Dresden comprises 12 residential units and one coach house with a small commercial unit. It supplies heat energy through a suction-injection well (two-well system) and a heat pump. The groundwater solution allows the owners to achieve this for a long-term period and at economical operating costs. Suction wells and injection wells were located in the courtyard of the old building. Extensive radiators were built in the apartments such that heating could be done with at low inlet temperatures. The project is a model for how heat pumps can be suitably used and how even existing properties can achieve an outstanding degree of energy efficiency.