Freiburg’s city hall operates as a surplus‑energy building, generating more energy than it requires for heating, cooling, ventilation and lighting. The building combines high‑performance thermal insulation with low‑temperature heating and high‑temperature cooling to reduce overall demand. A ventilation system with heat recovery further limits energy losses.

The building uses ground‑water energy for heating and cooling, supported by a heat pump and a plate heat exchanger. Solar energy panels installed on the roof and sun‑exposed façade surfaces supply electricity and contribute to shading. Photovoltaic units produce more electricity than the building consumes, enabling surplus power to be fed back into the grid.

This approach illustrates how integrated renewable systems and demand‑reduction measures can support surplus‑energy performance in public buildings. The project demonstrates the potential of combining insulation, heat recovery and on‑site solar generation to reduce operational energy needs.

Key figures:

• Building condition: Constructed or refurbished in 2017
• Building type: Public administrative building (city hall)
• Building age: 2017
• Primary energy consumption: Not specified in the source
• Energy performance certificate rating: DGNB Climate Positive
• Renewables: Photovoltaic panels; ground‑water energy used via heat pump and heat exchanger; solar energy panels on roof and façade

_{Image source: World Green Building Council (Image by H.G. Esch)}