Central Cooperative Union - Bulgaria


инж. Емил Георгиев Цаков, инж. Соня Господинова Георгиева






София, ул. „Георги Сава Раковски“ № 99

Modernisation and reconstruction of the COOP corporate and office building, Sofia

The reconstruction was completed at the beginning of 2018 and represents stage two of the finalisation of the entire COOP architecture group in the centre of the capital city, which includes the modern headquarters of the Central Cooperative Union and the COOP Hotel, built in the spirit and traditions of old Sofia from the 30ies of the 20th century.

The group is located in the very heart of the capital city – in the block locked between G. S. Rakovski, Iskar and Paris streets. It is in immediate proximity to many governmental and municipal administrative buildings, which makes it suitable for corporate building and offices, offering a array of contemporary administrative and business services.

The office building was built in the period 1969-1975 in line with the cutting edge construction and architecture standards at the time. It is a composition of 4 bodies of various heights: a 14-storey structure, two low-rise structures (6 and 7 floors) and a one-storey structure (restaurant), which are functionally connected and share an entrance. The total built-up area covers 1 310 sq. m., and the total built-up area on all levels - 10 393 sq. m.

The main entrance is from G. S. Rakovski str., and the employees' entrance is from Paris str. The access to the building is equally convenient via a personal vehicle or via various types of public transport.

Reconstruction of the building

The survey of the structure showed that the reinforced concrete framework structure is in excellent condition and does not need repair. Therefore the reconstruction of the building included works aimed at enhancing the building's architecture and energy efficiency, and providing additional services to the employees and guests (shops, conference rooms, museum travel agency and other accompanying facilities):

  • Construction of a new suspended facade on the high-rise 14-storey and the low-rise 7-storey structures.

The architectural design of the reconstructed facade is stylish in line with the modern office building trends. The contractor under the project is TAL Engineering EOOD, a leader in this sector.

The new suspended facade consists of opening and fixed elements, which in combination with the vertical decorative elements and Etalbond roofs, give the building the image of a modern office, with a feel of comfort and enjoyable working environment. Glazing units with excellent light transmittance, heat insulation and sound-proof qualities, aluminium thermal break profile system and fire-resistant thermal insulation wadding were used during the reconstruction.

  • Heat insulation and repair of the facade of the low-rise 6-storey structure.

The facade of the low-rise structure is fully consistent with the vision of the other two structures and it fits aesthetically in the architecture and vision of the neighbouring buildings, located in Paris str. The eastern facade is Etalbond clad, and the remaining sides are covered with decorative mineral coating. Heat insulation was put in place.

  • New automatic entrance doors of the restaurant – one-storey structure, surrounded by buildings on all sides.
  • Major reconstruction of the lobby, construction of frames and panelling of the elevator doors on all floors, installation of controlled access system to CCU's corporate offices.
  • Addition of a new air conditioning system to the existing heating installation, thus ensuring independence and high energy efficiency.
  • Expansion of the capacity of the conference block through the construction of a new conference hall in the lobby.

The main conference block is located on the top floor of the building and it comprises: 100-seat conference hall with modern furnishing, equipped with contemporary communication and audio-visual equipment. The conference hall's functionality allows for separation of four stand-alone, sound- and noise-proof halls of various capacities; 3 conference interpretation booths, catering and coffee break buffet, wardrobe and spacious foyer are available.

With the construction of the new conference hall in the lobby of the building, the number of the separate conference rooms increased to 4. These halls have different capacity and functionalities.

  • Refurbishment of the offices.

The administrative offices were refurbished and they offer natural light and all the communications required – telephones, internet, copy centre on the 3rd floor, etc. The repair works on the roof, in the lobby and the common areas of the building were carried out simultaneously with the reconstruction of the facade.

  • Construction of new and repair of the existing shops and restaurants and cafes.

COOP cafe (2nd floor), restaurant with 3 halls of different capacities, where the VIP hall is fully refurbished, COOP shop (on the 2nd floor of the building) and BIOCOOP shop, opened in March, are in place to offer high quality services to the people working in the building. There is a covered outdoor garden, which is part of the entire architecture group, COOP Holidays travel agency, opened in 2018.


The technologies and materials used are fully compliant with the highest contemporary requirements and standards in the area of development of office buildings, they have the required quality certificates and meet the sustainable construction criteria for energy efficiency and low harmful emissions footprint.

The horizontal solid strips of brick masonry were preserved during the construction of the new facade of the high-rise 14-storey and the low-rise 7-storey structures. A suspended glass facade was installed in front of them, combined with composite material, in accordance with the approved architectural design. The space between the solid (breastwork) zones and the new suspended façade is filled with fire resistant heat insulation wadding.

The two decorative architectural elements along the height of the building and the decorative roof are made of steel structure with flat girders of rectangular hollow boxes.

Separating Knauf "W 362" fire protection elements, preventing the spreading of a fire and the penetration of smoke between the elements of the new suspended facade from one floor to the other, were put in place as a horizontal continuation of the inter-floor structure and vertical continuation of the surrounding walls of the evacuation staircase in the building.

The suspended facade was done by TAL Engineering EOOD. The highest class materials and technological equipment were used for their production and installation: Alumil M7 series facade system; 28 mm НР Royal blue tempered glazing unit with 90% argon-filled internal volume; Alumil M valve, lining of aluminium composite material Etalbond tetra 4 mm, binding elements produced by „WURTH“, Germany.

The loading of the aluminium structure, the decorative elements and roofs is fully compliant  with the structure of the building and the requirements effective standards.

The laying of the heat insulation and the mineral coating of the low-rise 6-storey structure was made by Arko Engineering EOOD, using fire class "E" materials for the heat insulation and A2 for the finishing layer.

The air conditioning installation is brand new and it is in compliance with the  functionality of the building, which is centrally heated. VRF-type air conditioning installation (direct evaporation thermal pump system with alternating quantity of the cooling agent) was put in place for cooling in summer and heating during the transitional seasons. The systems envisaged are functional in the following temperature ranges – heating -200С to +150С external temperature, and cooling - -50С to +430С.

Low-noise aggregates installed on vibration-proof frames and rubber tampons are in place. The central air conditioning allows individual settings in the working premises, as well as centralised settings and control of the air conditioning system and its separate components.

The energy efficiency has improved significantly after the construction of the high-tech suspended facade, the heat insulation and the new DAIKIN air conditioning installation. The significant improvement of the heat characteristics resulted in a tangible decrease in the consumption of heating energy, respectively savings of the annual energy costs of the building. This was verified during the first year of operation, with heating energy cost savings amounting to 75%, and electricity savings – 5%.

Vertical communications are secured via 2 staircases and 4 elevators. The access to the building is controlled and 24-hour security and CCTV are in place.

The reconstruction and modernisation of the COOP office building and the bas-reliefs, symbols and logos built in the overall architecture group enhance the visibility of the cooperative organisations and are a demonstration of the sustainability of the cooperative business model and its lasting contribution to the development of the Bulgarian towns and villages.