The project was developed by the architectural workshops Atelier Hayde and Architektur Maurer, while the engineering component, including all aspects of resource conservation, was in charge of Vasko + Partner. Despite the fact that it took 3.6 million euros to bring the 77-meter tower to the PassivHaus standard (the budget totaled 84 million, about 2,000 euros / m2 of total area), and these costs will pay off only after 14 years, the customers went to this is through its Raiffeisen Climate Protection Initiative.
The "green" tower was built on the banks of the Danube Canal, in the Leopoldstadt district in the center of Vienna - on the site of the demolished OPEC office, which is very symbolic. There was already one Raiffeisen building nearby, so the new one was named RHW.2 (Raiffeisenhaus Wien 2). On the other hand, there is an IBM data storage and processing center, and this neighborhood turned out to be very beneficial for the new building. The silhouette of the tower, in addition to considerations of showiness, was determined by limitations: it was impossible to influence the natural light and shading of the facades of the surrounding buildings. A trapezoidal base is located on a triangular section in the plan, while the tower itself resembles a triangle in plan and with one "top" protrudes far beyond the base, forming a "visor" resting on the columns in front of the building entrance.
The 21-storey building is almost completely occupied by offices, while the base contains a 3-storey atrium lobby with a cafe and a Raiffeisen bank branch available to everyone, there are also medical and fitness centers, a canteen for employees and a kindergarten with a separate entrance, open not only for the children of bank employees, but also for residents of the adjacent neighborhoods. In addition, a conference center is located on the two upper floors, the main room of which is a hall with panoramic glazing, from where a spectacular view of Vienna opens up.
On the side of the canal embankment, under the "canal" there is a "plaza", and there is also an elevator open to everyone, which allows you to conveniently go down from street level to the promenade along the water. Also in RHW.2 there is a 6-level underground parking for 259 cars (total underground area of the building is 14 550 m2, aboveground - 27 600 m2).
The frame of the tower is made of reinforced concrete: the load is carried by round columns, in the center there is a "rod" with communications. The compact volume works to reduce heat loss. As the facades are glazed, the main challenge in achieving the PassivHaus standard was to prevent the interior from overheating due to the heat of the sun as the tower faces west. Therefore, the building was equipped with a double facade: its inner layer consists of opening Schüco windows with triple glazing (50/75 mm), then, in a gap of 625 mm wide, sun screens are installed (they are controlled by an automatic system), and the outer layer is formed by glazing from laminated panels with glass slats (16 mm).
The next goal of Vasko + Partner's engineers was to reduce energy consumption by 50% compared to a typical office building of the same size. This made it necessary to organize the production of energy in the building itself. The basis for this was the in-house biogas trigeneration CHP plant located below ground level, providing RHW.2 with heat (40%) and electricity (60%). Solar panels on the roof (1% of electricity) and a ground source heat pump (7% of heating) are also used for this purpose, but much more important is the heat generated by the IBM servers in the neighboring building: they cover 38% of the tower's needs. 28% of the cooling of the premises is provided by the water of the Danube Canal, the remaining 72% is handled by various cooling units. However, natural ventilation through manually opened windows helps to reduce these costs. As a result, only 39% of electricity and 15% of heat comes from urban networks. The systems used include concrete core activation and mechanical ventilation with highly efficient heat recovery.
To save on electricity spent on lighting, LEDs were installed in the corridors and in the garage (this gave a saving of 50%), and efficient luminaires with a high level of directional lighting were used in the offices. Engineers even took care of such "unimportant" details as uninterruptible power supplies: modern models have saved 50,000 kWh per year compared to conventional ones. An equally important area of work turned out to be coffee machines, which consume an average of 200 kWh per year in standby mode each. By using timers, this amount was reduced to 35 kWh per year. On-demand lighting, braking ventilation systems during non-working hours, and so on were also commonly used.
Monitoring of all systems and all consumers (possible with a smartphone app) takes place in real time, with particular emphasis on error analysis and building monitoring at night and on weekends. Comparison with other projects is also provided.
According to the Austrian OIB Institute, the Raiffeisen tower commissioned in 2012 consumes 21 kWh / meter of total area / year, which corresponds to the A ++ energy class. However, such indicators, including the PassivHaus certificate obtained in the summer of 2013, are unlikely to be massively implemented for new construction both in Austria and abroad. Vasko + Partner engineers faced many problems during the implementation of their project, and not the least of them - insufficiently high quality construction. So, when the contractors reported on the readiness of the building envelope, during the tests it turned out that there are meter-long gaps in it, and in fact its maximum possible tightness is the basis of the entire PassivHaus concept. Of course, these and other shortcomings were then successfully eliminated, but it is still clear: RHW.2 is overcoming an important milestone, but the final victory of the PassivHaus standard in office construction is still ahead.
