“Yet, the perception of the architecture of the fifties [and sixties] is ambivalent, and the time interval for an objective assessment too short. Dealing with the structures of this time, spans between demolition and heritage conservation” That is how Helmut Lackner describes the architecture of the post war era and the problems between urgent need for modernisation and possible preservation of outstanding buildings of this time.(1)
Exactly this decision - renovation or demolition – had to be made by the Energie Steiermark, (built in 1961) whose headquarters in a premium location of Graz, were in urgent need of modernisation, particularly because the elongated plate construction with its nine storeys in no way represented the contemporary requirements of an energy-efficient building. The optimism of the post war modern architecture was not yet familiar with the problems of energy shocks or the decreasing energy resources. The lightweight construction of this period brought innovative technological solutions for prefabricated buildings, as well as utilization and form questions to the fore. Thermal insulation and modern building technology such as fire safety within the buildings were not available, since at the time no fire zones were prescribed. The existing building equipment was obsolete or defect and the interior atmosphere unpleasant.
Energy-efficient modernization of the 50’s and 60’s architecture
A previous scientific study by Andreas Ampenberger at the Department of Buildings and Energy, Technical University of Graz, was made of the headquarters of Energie Steiermark, for the purpose of developing optimal energy modernization proposals BEEP (Building Energy and Environmental Performance Tool). The initial situation was open to all possibilities – from modernisation and extension to demolition and new construction. A survey amongst the staff within the energy company showed a wish for a "moderate rehabilitation", where existing problems would be solved while energy consuming solutions -such as a complete new build- were rejected. Eventually, the board of management created guidelines that emanated towards a goal of an extension of 50%, the construction of an underground parking garage and the eventual energy consumption to reach the required level of a low-energy building. Ampenberger could thereby identify the benefits of a lengthwise extension as opposed to an annexe-like extension.(2)
Due to the plot area, a one sided annexe extension would have only allowed a height of five storeys, it would have partially decreased the solar energy gain and in addition; the existing garden area would have been considerably reduced.
The wish of the company however, was an enlarged park area and a possibility for green space above the underground parking area.
Architectural competition and project implementation
The tendered architectural competition requested the previously mentioned conditions, the incorporation of a 10th Floor for conference and seminar rooms and an energy exhibition space on the ground floor.
The aim of this extension was to unite the company positions which had previously been spread out at four different locations of the city, and to merge them with the corporate headquarters, which would thereby contribute to a significant save in terms of infrastructure. All 620 employees of the Group should operate in the same building.
Not least was the requirement to create a corporate identity for the company through the architectural design, to make a self-conscious positioning in the urban environment possible. Even the old building from the early 1960’s, monumentally symbolised the beginning of a “high rise –fashion” (Roland Rainer) and expressed economic upheaval which architecturally towered over the local area.
The selected design fulfils the tender requirements, not only in technical terms with a sophisticated energy system, especially the interior and facade design will contribute to convey the company headquarters as a cityscape formative.
Through the extension of the existing building, to the removal of everything but the reinforced concrete frame on both short sides, there were many safety-related synergies, such as significant improvements in escape routes. The extension of the existing building also offered the possibility of a new overall design of the facade, which has a sophisticated LED system which at night has high recognition value. Through its clear rhythm, the sixties architecture offered many benefits -both technical and aesthetic to the modernisation of the façade.
The aim, with the choice of energy-technical system for the 15,500 sqm extension of the office building, was a combination of overall reduction of energy demand and the use of renewable energy.
It was assumed that the energy consumption required for cooling the 1,500 workstations and the several technical devices would be considerably higher than the energy required for heating.
In total, 556sqm of photovoltaic’s covering the surface of roofs and facades could be accommodated, which produce an annual average of 70.000kWh energy. In addition to this, geothermal energy is used.
All toilet facilities are operated through rainwater harvesting which gives a water-saving of 1.8 million litres per year.
The water heating for domestic hot water is provided through a solar power system which in combination with the new well-insulated walls (18cm mineral wool) makes the building reach energy efficiency class A (22.8 kWh/m2a).
For the façade, a zoning of the surface was created: glazed areas with folding shutters for shade, that work with specially shaped elements in the skylight area for adjusted daylight use. Through this, a light deflection occurs due to reflection, which lets the daylight deep into the rooms. The artificial work space illumination is provided by floor lamps which are automatically adjusted depending on daylight. This alone contributes to an energy saving of about 45%. A further energy efficiency improvement lies in heat recovery, to ensure that the required energy is minimised.
The comfortable atmosphere in the offices, which vary from individual offices to larger rooms can be adjusted individually by the employees, at a range of + / - 2 ° C.
Windows can be opened but this automatically causes entire heating/cooling system to shut down.
The pleasant atmosphere is interiorly highlighted by a sophisticated colour scheme in all of the floors and continued in the extended garden area with its more than 100 trees.
The implemented design transformed a high-rise building of the post war modernism in urgent need of redevelopment into an e-office with a unique model of its kind in terms of energy efficiency.
The fact that the design has an inherent part of the energy-related solutions was confirmed by the recognition award of the solar energy development association Bavaria (SeV) in 2011, that distinguished the submitted "" Energie Steiermark "project.
Use of the building: • Company headquarters of Energie Steiermark
Extension of former Steweag premises: • Old building constructed in 1961 • Very poor heat insulation, dilapidated windows, no fire protection (no fire cuts etc. - were not required at time of construction) • Obsolete and malfunctioning building services • Enlargement of the old building by 50% (old building 40x20m + extension 20x20m) • Complete gutting of the old building - leaving only the support structure of the steel skeleton • Removing costs of a total of 4 premises in the Graz area (less commuting, considerable reduction of infrastructure costs) • Total of 620 employees on the premises
Further construction measures: • Underground parking to the west with split-level construction, 3 underground levels in the eastern part next to the office building and 2 underground levels in the western part • Newly constructed underground parking with 246 places • Difficult construction involving underpinning of existing buildings and securing of high-rise buildings on the neighbouring plot • Theme of “parkland instead of parking“ - previously the western area of the courtyard was completely used for parking whilst there was a three-storey office building in the northern part, which was demolished • Park paths where laid immediately, with a 2m layer of soil above the parking garage in order to ensure the possibility of tree growth • Construction of a 10th floor for conference and seminar rooms • “E-Wunderwelt” (E-wonderworld) on the ground floor
Architectural concept: • Competition tender, winning project Giselbrecht+Partner • Good usage of construction site and extension of the existing building • A confident and unmistakeable profile within the image of the city of Graz • Façade concept with folding shutters, thus the façade will look different every day • LED-façade - presenting a profile to the city at night-time too with a scenario that relates to energy (extending the day with a rising sun, rain, waterfall, forest – those very energies from which all life springs) • Interior colour concept - unmistakeable colours for each storey, helping employees to identify with ‘their’ floor • Interior design ranging from single offices to group office solutions
Alternative energy, technical specialties: • High interior heat load due to large number of people, many devices (PCs, screens etc.) lead to a considerable demand for cooling, heating demand rather low (total heat output incl. ventilation 800kW; low cooling power since folding shutters serve as sun protection - total 650kW) • Photovoltaic 556m² installed in the façade, on the roof and in the canopy of the entrance, with a total output of 78kWp, annual output of approx 70,000kWh • Geothermal - energy via geothermal boreholes for heating and cooling, 1200m deep boreholes, delivers under-floor heating and pre-cooling of ground floor and 10th floor • Use of rainwater for toilets, saving 1,800,000 litres of drinking water/year of flushing. Storage of rain water is in three tanks on the 3rd basement floor of the new building with a capacity of 350m³, with toilet supply via the sprinkler system pipework • Solar plant with approx. 56m² delivers warm tap water for 1st floor, ground floor and assistance to under-floor heating on ground floor and 10th floor, annual solar yield is approx 21,500kWh • Façade - very well insulated façade, insulation thickness 18cm of rock wool (22.8kWh/m²a heating requirement = energy class A) • Shading system – folding shutters prevent sun’s rays from hitting the glass - heat input in the summer is reduced considerably • Redirection of light - specially shaped ceiling light, which reflects daylight to the ceiling thereby redirecting it deep into the offices • Workplace lighting by means of standing lamps - light intensity is automatically controlled by level of room light; on/off switch by means of sensor also automatic - no need for staff to switch light off. This saves around 45% percent of energy in comparison with conventional lighting • Heat recovery in ventilation - 12 ventilation centres with an overall fresh airflow of approx. 86,000m³/h for the entire E-office, are equipped with a cross-flow heat exchanger having a heat recovery of approx. 80%, thus reducing additional energy requirement to a minimum. Office ventilation was laid out for hygienic change of air at approx. 35m³/h per employee; employees have the facility to make minor adjustments to room temperature (+-2°C). • Window contacts - windows can be opened but, if a window is open, the air conditioning (heating/cooling) is automatically suspended in that room