Galaxy 21

The office building located on Praterstraße in the 2nd district of Vienna, built in the years 1974/75, underwent revitalization and expansion according to the plans by Martin Kohlbauer.

The present project involved the demolition of the two technical floors and the addition of 6 new floors ("Skyline levels") with an elliptical layout.

The 6 new floors were constructed in reinforced concrete on top of the existing floor above the 15th floor, with the load transfer of the expansion achieved through a new column system integrated into the old building and supported in the 1st basement.

Up to the 2nd floor, the layout has a right-angled triangular shape with side lengths of approximately 52 meters. From floors 3 to 15, the layout becomes a rectangle with added bay windows, measuring 31 meters x 36 meters in exterior dimensions. The newly added 6 floors have an elliptical layout with axis dimensions of 29 meters x 34 meters.

The office building was designed with flexibility in mind, providing options for subdividing the space into individual cells, group offices, or open-plan offices. A restaurant with public access for approximately 150 people was installed on the ground floor.

The façade underwent a complete renovation, and the new appearance of the building is characterized by its new glass exterior. It features opaque glazing in the parapet areas and "White Box" glazing in the solid areas of the original structure. Post-and-beam construction was chosen for the base zones, while the Skyline levels have a radial full glazing system. The façade exhibits excellent thermal and acoustic properties, and despite the high wind load, the windows in the upper floors can be individually opened.

The Galaxy building was optimized for building physics, resulting in significant improvements in thermal insulation, sound insulation, and operational efficiency. The overall concept aligns with the standards of a low-energy house.