Sustainability has become a trend for all areas of human life in recent years, so it is natural that this trend has been reflected in the construction industry, where building construction standards have continuously been raised in order to correspond to the new requirements of sustainable development. Architects and construction companies constantly face new challenges concerning improvement of their building projects in order to satisfy the latest regulations and certifications. The more restrictions and regulations emerge in the field of buildings construction, the more challenges the professionals have to face, which pushes them to look for innovative ideas and techniques. The design of highrise buildings is even more challenging and complicated in the context of construction methods in correlation with sustainability principles and taking into account the recent extreme weather fluctuations caused by global warming. Unlike the buildings of regular height, high-rises do not offer such a wide range of possible materials to be used in construction and are more limited to the standard monolithic reinforced concrete skeleton type of the load-bearing structure. It gives them less flexibility and limits the opportunities to achieve the necessary sustainability level. These kinds of challenges during the design process of a high-rise building require more creativity from the architects and stimulate research towards of innovations.
Therefore, the aim of this paper is to analyse and compare two newly constructed high-rises: Twin City Tower Bratislava and HoHo Vienna (Holz-Hochhaus – “Wooden High-rise” in German). Both of them comply with the latest building standards and share a range of common characteristics:
- climate zone (located 46 km away from each other),
- situated in dense urban environment in a capital city,
- urbanism is based on a concept of a sustainable city,
- the buildings are used for commercial purposes (multi-purpose),
- modern construction (Twin City Tower completed in 2018; HoHo completed in summer 2019),
- high-rises (Twin City Tower Bratislava: 23 floors, 89 meters high ; HoHo Vienna: 24 floors, 84 meters high ),
- floor area (Heated floor space 34,500 m2 in Twin City Tower Bratislava; 25,000 m2 in HoHo Vienna),
- both projects have received the green building certification (BREEAM Outstanding certificate for Twin City Tower Bratislava, which is also registered//has an application for WELL Core & Shell Certification; Gold Certificate by LEED for HoHo Vienna, Core & Shell Certification).
Despite many similar features, there are two major differences between the two structures, which are the use of materials and the construction methods. The structure of HoHo Vienna predominantly (about 75%) consists of local natural material – wood, while the Twin City Tower has a structure typical of high-rise buildings – a monolithic reinforced concrete skeleton with concrete ceiling slabs and a fully glazed facade. Twin City Tower uses proven building materials and procedures for its constructive solution, with the aim to improve and increase their useful life. In contrast, HoHo tower uses new experimental building solutions and combinations of materials. Nevertheless, both buildings comply with strict sustainability requirements as well as requirements for a healthy indoor environment. Therefore, the authors of this study compare these buildings, their constructional concepts, energy concepts and ecological solutions and analyse the differences and similarities, while keeping the focus on sustainability solutions.
“Sustainable development is a term that everyone likes but no one is sure what it means.”