Typology Transformation of an office building – office, conference, retail, bicycle garage Location Cologne Construction volume 17,040 m² GFA, 61,775 m³ GIA Client PROXIMUS REAL ESTATE AG, Quantum Immobilien AG Architect kadawittfeldarchitektur Planning from 2020 Realisation from 2023 Competition 2020 – 1st place Certification DGNB Gold targeted
#Transformation of an existing property from the 1960s into a sustainable, contemporary office building. Despite structural deficiencies and the option of new construction, the existing building will be revitalized, thereby avoiding around 2,000 tons of CO2 emissions.
The office building is located just 1.5 km from the cathedral, at a busy intersection in Cologne city center.
Mit kleinen orthogonalen Rücksprüngen passt sich das Gebäude zukünftig an den geschwungenen Straßenverlauf der Magnusstraße an.
Central Cross, Cologne | Germany The 12-story office building is located in a prominent position in Cologne’s city center, on Friesenplatz—just 1.5 kilometers from the cathedral. Built in the 1960s, it no longer met today’s comfort requirements. After standing vacant for years, demolition and reconstruction seemed inevitable. It is thus representative of many buildings of its time. Despite its structural weaknesses, such as low floor heights and limited load-bearing capacity, it has nevertheless been preserved thanks to differentiated, coordinated, and in some cases unconventional measures. The revitalization has created a contemporary, flexible office building with a high level of user comfort, low life-cycle costs, and low CO2 emissions.
In addition to its functional shortcomings, the existing building caused numerous urban planning problems: the recessed ground floor zone at the intersection created a dark, neglected area right next to the subway entrance. An important goal of the revitalization was to remedy this situation, which, together with the uninviting façade, had a negative impact on the surrounding urban space.
The existing building had numerous functional, design, and urban planning issues.
Right next to the subway entrance, the recessed low ground floor created a problematic urban planning situation.
View from Friesenplatz of the revitalized office building with its striking new transparent facade.
To enhance the urban space, cafés and retail space are being created on the ground floor, and the recess at the intersection is being generously expanded to two stories. This will create sufficient space for pedestrians and cyclists around the subway entrance. Two cafés will revitalize the former wasteland and provide 24/7 lighting for the public space.
With its copper-colored facades, the complex will reshape the urban landscape after its revitalization. The first floor will be demolished at the intersection, creating a spacious, open urban space that will be enlivened by cafés and illuminated 24/7. With its transparent, horizontally layered facade, which varies in appearance from transparent to opaque copper depending on the perspective, and its spectacular cantilever, the high-rise building will become a new landmark.
The previously problematic ground floor area will be expanded to two stories and revitalized with cafés and shops.
The 12-story high-rise and its annex on Hohenzollernring will be preserved and revitalized. New double facades, flexible working environments, CO2-optimized building services, and green open spaces will ensure contemporary working comfort in the future, while the new roof terrace will offer a fantastic view over Cologne.
The low-rise building on Friesenwall will be demolished due to its unsound structure and replaced by a new building. In the inner courtyard, the demolition of the first floor will improve lighting for the surrounding buildings, and a three-story extension will expand the high-rise’s potential uses.
The new complex consists of three structures: the existing high-rise building, its annex, and an additional building on Friesenwall, which enclose a green inner courtyard above the ground floor at the rear.
The revitalization will preserve around 70% of the concrete structure, saving 2,000 tons of CO2 emissions.
The existing buildings will be stripped back to their supporting structures. The solid parapets will also be removed to create the load-bearing capacity required for a modern, soundproof double facade. The new facade will also significantly improve the lighting in the interior.
Revitalization
The impressive, spacious foyer, cafés, and retail stores on the ground floor create an attractive surrounding urban space. Above, surrounding the green inner courtyard, are the office spaces with the new attic floor and the roof terrace at the top.
The clear room heights of the existing buildings (2.70 m) are incompatible with today’s standard solutions for highly installed building technology, which was one of the reasons why demolition and reconstruction of the existing buildings was initially preferred. However, open cable routing without suspended ceilings will allow the buildings to continue to be used. The conditions for this are created by the sound-insulating double facade, which allows natural ventilation up to the top floors, and decentralized ventilation modules.
The additional buildings will be constructed with standard room heights in line with today’s requirements. Meeting points with a special atmosphere will be created at the transitions, and the split level will generate exciting interior perspectives in the open office structure.
The revitalization will create a contemporary office building with open structures, high flexibility of use, and a variety of meeting and communication areas. Green outdoor spaces on almost every floor offer opportunities to take a quick breath of fresh air, hold informal meetings, or even small outdoor conferences.
Green inner courtyard
The inner courtyard and roof areas will be intensively and partially extensively greened. They will offer employees outdoor areas for relaxation, communication, and socializing. At the same time, they will increase the amount of green space in Cologne’s highly densely populated city center, help improve the microclimate, bind fine dust, cool the environment, and promote biodiversity.
View of the new, landscaped inner courtyard.
As part of the revitalization, new green spaces are being created in the inner courtyard and on the roof areas, which will be open to all employees.
sustainability concept
The new, sustainable energy concept reduces CO2 emissions by around 53%. A renewable energy-powered outdoor air heat pump regulates the temperature in the building, while peak loads in the sales areas are covered by district heating. Photovoltaic systems on the roofs supply electricity for the building’s own use and for operating the heat pump.
The ventilation concept makes a significant contribution to CO2 reduction: despite the high level of traffic noise, the double façade enables natural, individually controlled ventilation, which is only supported by efficient, decentralized ventilation systems. The green roofs and the inner courtyard provide shade and cooling in summer and improve the microclimate.
Facade
The striking, delicate, vertically scaled double facade characterizes the new building complex. Depending on the perspective, its appearance varies from transparent to copper-colored opaque. It is highly insulating, allows high light transmission, and, despite high noise emissions, provides natural, individual ventilation. Optimized for north-south orientation, solar energy is used in winter and overheating is reduced in summer. Sun protection is integrated and protects against overheating even in windy conditions.
Testing the new Facade on the working model.
Facade samples in different scales: In addition to the “hand sample,” Feldhaus created a 1:1 mock-up to simulate the final effect and determine the final color tone.
