Located between Wagramerstraße and Kratochwilestraße and adjacent to the "Alte Donau" metro station, the 60m high SEG - Tower from COOP HIMMELB(L)AU forms in conjunction with two other projected high-rise buildings the new district "Donau - City". The tower includes 70 apartments, 9 eating facilities, offices and practices on 25 floors.The complete arrangement captivates by its immediate nearness to the city core and the shopping center "Donauzentrum" as well as by its location in one of the favourite leisure districts of Vienna. It is also captivating due to its striking height and its quality of space, which is determined by different typological concepts.Two major considerations were important for the design of the outer form of the COOP HIMMELB(L)AU building:On the one hand the concept of the tower is based on the idea to put two houses, one on top of the other, in a way such that a common space would occur at the intersection. This common space - called a sky-lobby - is then used for the accommodation of a venue, a playground, a "teleworking café" and a sundeck. On the other hand the concept of the so-called climate facade was developed, which is the linking and surrounding element between the two components.This is an "intelligent" glass facade that regulates together with the "air - box" on top of the roof and the circulation core (planned as heat accumulator) the cooling of the apartments in summer and the heating in winter. This well calculated system offers a higher level of comfort during hot weather and a minimizing of costs during the heating period. Besides its function as a sound protection, the climate facade provides space for glazed loggias placed in front of the apartments and comprising two or three floors. These loggias allow green spaces, not normally seen in high-rise buildings, and a view to the city and to nature, also uncommon for urban living.The concept of the glass skin surrounding the building enables an orientation of all buildings towards south.All apartments (ranging from 55m2 to 130m2) are based on a loft concept with an open plan and without load-bearing walls. This concept enables a flexible layout of all the apartments. A concierge located in the two-floor entrance lobby will provide optimal service for all the inhabitants.Concept of the Climate facadeThe glass facade, developed from the architectural concept, is intended to passively exploit solar energy. Thus less initial investment for the energy system is needed and the amortisation period would be considerably shortened.It is also planned to power compressor engines by means of wind energy, which would provide necessary air circulation in the building.Passive Energy Concept:The glass facade is the medium through which thermal energy will be stored as radiant energy potential during winter, spring and autumn. The facade faces southeast and southwest. The thermal energy produced during daylight hours will be supplied to a thermal reservoir unit located in the interior of the building. In this way, a milder, more equitable room climate as compared to the exterior conditions will be created in the areas of the building directly behind the climate facade. The exploitation of solar energy will lead to a considerable reduction in total energy consumption. This is effected on the one hand by the stabilisation of the differences in temperature between the interior living space and the loggia area, and on the other hand by the direct supply of energy to the apartments from the thermal reservoir inside the core area of the building.Thermal Mass:The central thermal mass is to be a reinforced concrete shaft. To expedite the energy exchange process, this shaft will be equipped with heat exchange surfaces, also made of reinforced concrete.To guarantee heat exchange between the loggia area and the climate facade, air circulation between the two system areas will be provided mechanically. This air circulation will be effected by the ventilators in the thermal mass shaft.