Margravial Palace, Karlsruhe, Germany

After being nearly completely destroyed during World War II, the former palace was rebuilt in the 1960s in line with the era’s architectural style, later expanded and partially renovated. The recent renovation preserves the historic façade, including the vaulted cellar and some interior walls. New structures built using a hybrid timber-reinforced concrete method include the side wings and large parts of the central section, with the existing framework defining the floor heights and circulation. The building features a basement, ground floor, three upper floors, and two attic levels, arranged around the main structure with side wings. The basement houses underground parking, storage, technical rooms, and auxiliary spaces. The ground floor in the side wings functions as commercial space, including restaurants and a bistro. The three upper floors of the side wings are designed for commercial use, such as offices. The main building, with double-height rooms, accommodates various spaces for meetings, conferences, and events on both the ground and upper floors. The attic levels contain maisonette apartments with large winter gardens, serving as buffer zones between indoor and outdoor spaces year-round.

The primary goal of the concept is to provide the highest possible quality of stay while minimizing Carbon emissions throughout the entire lifecycle. To achieve this, Transsolar prepared carbon footprint analyses for building operation and energy costs, conducted solar radiation and daylight studies, and developed the overall energy concept together with Transplan.

On-site renewable energy generation is enabled by a groundwater well. A water-to-water heat pump raises the temperature to a low-temperature heating level. Additionally, connection to the Karlsruhe district heating network supplements the heating supply. A large share of the building’s cooling demand is covered by the groundwater well through free cooling. Thanks to a switchable hydraulic configuration, the heat pump can also provide low-temperature cooling when needed. If peak loads exceed the capacity of the well, the heat pump automatically switches to compression-chiller mode. In this case, any surplus heat is rejected to the outdoors via a cooling tower, unless it can be used elsewhere within the building.

Photovoltaic panels installed on the roof generate renewable electricity, offsetting Carbon emissions. The roofs are clad with slate and feature discreetly integrated solar modules. Maximizing PV surface area on the roof enables predominantly climate-neutral building operation.

In the commercial areas on the 1st to 3rd floors, a full mechanical ventilation system was intentionally omitted. Instead, natural window ventilation in combination with underfloor convectors along the façade ensures a well-balanced airflow. This approach remains intuitive and individually adjustable for users while reducing drafts during ventilation. Decentralized supply and exhaust air systems in the ground-floor commercial areas allow tailored responses to different usage requirements. Additionally, any resulting loads are compensated by ceiling-mounted or façade-near underfloor convectors. These are also intended for space heating.

For areas with high occupancy, such as event venues and meeting rooms in the central section, a mechanical supply and exhaust ventilation system is intended, working in combination with radiant heating and cooling ceilings.

In the apartments, fresh air is introduced through window vents and extracted centrally. Underfloor heating provides comfortable indoor temperatures during winter. A refined solar shading concept featuring micro-blinds and sliding shutters ensures thermal comfort in summer. Additionally, the apartments can be cooled using ventilated fan-coil units.