The new development is sited on Seoul’s main boulevard, Sejong-ro Avenue, at Gwanghwamun Square, in the thick of Seoul’s numerous landmarks and with the mountains as backdrop to the north. Immediate architectural neighbours are the Sejong Center for Performing Arts, and, at the head of the Avenue, the former royal Gyeongbok Gung Palace (built in 1395) and the Blue House (the president’s residence), giving the site great prominence within the urban fabric of the city.
Currently on site is phase one of the project, the KT Cheongjin Building and the taller of the towers, situated at the back of the Sejong-ro Avenue site. The second tower, KT Gwanghwamun Building, will be constructed in a second phase. The two will be linked underground, giving access to Seoul’s bustling underground shopping malls and metros.
Both buildings are broken down into pairs of 23m x 23m (75ft x 75ft) towers, which are linked by glazed circulation spaces (for horizontal as well as vertical circulation). In both, the panoramic lifts are housed in a subsequent pair of slender structures to one end. The structural 10m x 10m (33ft x 33ft) concrete cores have been pulled into the very centre of both buildings, leaving huge open-plan spaces around the exterior edges. This means that all offices have a high degree of natural light, quite apart from expansive views of the city and the mountains beyond.
The towers rest on a series of slender pillars, allowing them to float above the ground-level gardens. This, coupled with the breaking down of the mass of a tower into groups of slender towers, creates an extraordinary feeling of lightness and almost fragility for such tall buildings.
The first tower to be built, the KT Cheongjin Building, will be 110m (360ft) high, numbering 25 storeys, and will provide 25,000 sq m (270,000 sq ft) of useable space. It is formed of a pair of 23m x 23m towers facing west towards Sejong-ro Avenue. At the back of these is the pair of slim lift-shafts, affording views out to the mountains.
The KT Gwanghwamun Building, fronting on to the main Avenue, will be a little lower at 82m (269ft), but will comprise four of the 23m x 23m towers, again with the lift shafts taken out, this time placed to the south of the building. The 18 storeys of this tower will provide 30,000 sq m (323,000 sq ft) of useable space.
Addressing the climatic factors (very cold winters, very hot summers, frequent typhoons and high humidity), the buildings are sealed with double-skin facades. The required 40% quota of facade opacity is provided by white glass, insulated behind; the remaining 60% ‘crystal’ facade is totally transparent. The whole is clad in a second skin of white metal louvers, providing shade and protection against solar gain.
The KT Cheongjin Building is due to be completed by end 2014, followed by the KT Gwanghwamun Building by 2017.
Client: KT Corporation
Renzo Piano Building Workshop, architects
in collaboration with Samoo Architects and Engineers (Seoul)
Design Team: B.Plattner and Erik Volz (Partner and Associate in charge), and T.Sahlmann with T.Gantner, C.Kimmerle, A.Lerpinière, C.Portelette, H.J.Sim, J.Sung and E.Marin, T.McKeogh; O.Aubert, C.Colson, Y.Kyrkos (models)
Consultants: Bollinger + Grohmann, Chunglym Structural Consultants (structure and façade); Arup, Samoo Mechanical + Samoo Electrical Consultants (MEP and vertical transportation); Arup (sustainability, special lighting), Fontana (landscape architect), Hanmi Global (construction manager), GS (construction company), Dawin (interior design)