Raiffeisenbank im Rheintal
STARTING POINT
The basic fabric of the building of the Raiffeisenbank Im Rheintal (previously known as Raiffeisenbank Dornbirn) is made up of three different building phases. The original building, which dates from 1956, was extended in 2 stages: along Stadtstrasse (1973) and along Viehmarktstraße (1990). The building as a whole consists of two parts, the main volume, which faces north-south, stands parallel to Stadtstrasse, while the smaller ancillary building on Viehmarktstraße runs from east to west.
With the construction of the Stadtgarage (an underground garage) in 2008 the bank was given the opportunity to create a direct connection to this new garage. This signalled the start of major rebuilding works on and in the entire building. The building works in the basement were carried out parallel to the construction of the Stadtgarage. They were followed by the recently completed building phase which included an comprehensive thermal retrofit of the building, the adaptation and conversion of the 4th floor from apartments into offices, the addition of a further floor, and the redesign of the facade. Additionally in the storeys used by the bank (1st and 2nd floors) changes were made to the office layout and the fittings. In the course of this work the building services, security and electrical systems were renovated. All the energy demands for heating and cooling the building are now met by the use of geothermal energy.
THERMAL RETROFIT
Resulting from the fact that it was built in several phases the building no longer satisfied the building regulation requirements with regard to thermal insulation. In addition providing the amount of energy needed to cool the building resulted in high running costs.
One of the client’s main concerns was to optimise the entire building in energy terms. Consequently the goal set was to bring the existing building, in terms of energy consumption, up to level of a modern low energy building. While the building was still being used the envelope of the part on Stadtstrasse was completely insulated (with 22 cm of thermal insulation) and all the existing windows were replaced by triple-glazed timber and aluminium windows. Together these measures upgraded the entire building to energy class A.
ADDITION OF A STOREY
The newly created roof top level, which is used by the bank for meetings, further training courses and events, has a capacity of around 110 persons. When necessary the large open space can be divided by means of a mobile partition wall into a foyer and a separate meeting or events room. The service rooms are compactly organised around the circulation core.Areas of floor to ceiling glazing offer a panoramic view across the centre of Dornbirn and the surroundings. The new storey is shifted back in relation to the line of the east and north facades to create room for a generously sized roof terrace. This additional floor is timber-built with spans of up to 10.7 metres. It rests on a grid of reinforced concrete beams that distribute the additional loads and direct them into the existing building.
FACADE
A changeable external skin – both the source of shade and a design element – is placed over the existing facade. It consists of vertical swivelling shutters of natural anodised aluminium which when opened, at alternating distances of 40 and 80 cm apart, lend the building a new rhythm. The building gets a new vertical expression. The shutters on each floor are of a different height, giving the six-storey building a new scale. If the shutters on the south and east facades are closed the perception of the building is changed completely. The emphatically vertical articulation of the facade, which is accompanied by an impression of depth, changes and the building acquires a flat appearance, the shutters forming a closed, protective skin.
From outside this skin seems opaque. From inside the perforations in the metal allow an unhindered view outside. The close spacing of the perforations allows light to enter while reducing solar gains on the facade.The shutters are operated automatically in accordance with the weather conditions. The users can, however, intervene manually in order to close or open the shutters when and if they wish. It is not only the mechanical movement of the shutters that alters the way in which the building is perceived: the restrained basic colour of the anodised aluminium building envelope can change as a result of the changing light conditions at different times of the day and in different kinds of weather. The redesign of the facade stands for two terms: innovation and identity. In this project it proved possible to harmonise, in an innovative way, the function of providing shade with design criteria. The “new” headquarters of the Raiffeisenbank Im Rheintal presents itself as an unmistakeable urban element in the centre of Dornbirn.
FACTS
Number of swivelling shutters: 623, combined in 40 control modules that automatically track the position of the sun
Facade metal: 3 mm natural colour anodised aluminium with grid perforation 3-6 mm, light transmission ca. 23% Facade construction period: January to October 2010
Total construction time: September 2009 to November 2010
Deep drilling: 28 geothermal probes, each ca. 120 metres
Heating energy requirement [before refurbishment]: ca. 70 kWh/m2a (this represents about 7 litres of heating oil per m2 of heated usable floor area)
Heating energy requirement [after refurbishment]: 20 kWh/m2a (this represents about 2 litres of heating oil per m2 heated usable floor area)
Cooling energy requirement [after refurbishment]: 25 kWh/m2a (ca. 1/25th of this energy is required to supply the heat pump)
