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ENERGIE AG / LINZ, AUSTRIA



CLIENT: Energie AG

SITE: One (small) city block near the train station and across the street from the Volksgarten, at the edge of the industrial part of the city

PROGRAM: New corporate headquarters for Austrian energy utility: offices, support areas, call center, conference/seminar area, auditorium, sales area, structured parking

SIZE: 18,000 sq. m (180,000 sq. ft.)

COST: ATS 356 million ($33 million)

COMPLETION: Summer 2005 (competition)

NOTES: Cast-in-place concrete construction throughout on mat footing; active/passive solar louver system and building geometry

PROJECT TEXT: All life and energy comes from the sun. An energy company should celebrate this fact: with the sun as its spokesman, every beautiful day becomes an advertisement for Energie AG.

As a tower, the new Energie AG headquarters can maximize its effects as a sign for itself and gateway for the city. Of all possible building typologies, the tower has the most personality, and it is appropriate for Energie AG’s tower to seem energetic. This tower expresses its energetic personality by “turning” or “twisting” its form in response to environmental stimuli and urban responsibility: one of its faces is rotated toward the sun and the other toward the center of Linz; most of the overt design effects follow from this simple gesture.

This urban-scaled architectural “branding” gesture also maximizes building-scaled energy performance. A tower provides the greatest surface area for absorbing energy from the sun and dispensing views and fresh air for the employees. By heliotropically turning a broad face to the sun the building increases the magnitude and efficiency of beneficial energy exchange across its depth. Signaling its technological nature, the sun-worshiping south facade wears intelligent shades that tune the incident energy, separating the light and heat and sending both where they are needed in the interior. In contrast, the north facade overlooking the park and central Linz is rendered as a pixilated image of the sky, with the scattered pattern of windows creating a dappled sunlight effect on the interior. Despite the apparent free-form arrangement of this fenestration it is designed to ensure that each potential office space receives a maximum amount of natural light, views, and ventilation.

The building is large but is still a good neighbor. The plinth at the base eases the bulk of the tower into the urban fabric. No holes are left, no windswept empty plazas, and no colonizing of surrounding open space. This plinth provides a private outdoor area for the employees, a quiet winter-garden sheltered from the north wind by the tower and from the hustle and bustle of the street by its elevation above it all, and a natural breakout area for the event spaces, without intruding onto the surrounding public spaces or redirecting traffic.

Inside, the tower is all elegant business; like a flower it is organically organized into an internal core/stem that conducts energy vertically—human and physical—and perimeter/petals that absorb and expend that energy horizontally. With sliding glass partitions along the corridors and dramatic three-level atria in the core, the flexible privacy of the cellular office layout on each floor is complemented by a larger connective transparency. The corridors to the north and south are not isolated from each other, and every floor feels like it is part of a larger whole.

The basic structure is cast-in-place reinforced concrete, laid out in an eight-meter equilateral triangular column grid with monolithic central cores; however, the “twisting” of the tower introduces three zones of special consideration: 1) inward-sloping concrete columns integral with the general building frame along the south facade carry the overhung gravity loads gradually inward, minimizing the vertical and lateral structural impact of the lean to the south; 2) a dramatic cantilever of the southeast corner of the structure over Kaertnerstrasse is supported on two-story triangulated (vertically) frames/struts at that side with the load being reduced by the location of the external steel fire stair at that location and the elimination of interior space and office loading; and 3) a long-span condition on the sloping Coulinstrasse facade providing larger interior volumes for the event space and customer area is achieved with steel trusses integrated geometrically into the general grid of the cast-in-place structure.

The building skin is envisioned as a natural energy interface, absorbing and deflecting ambient energy as appropriate to achieve the greatest efficiency. To enhance its abilities in this regard, the building turns to face the sun, spreading a broad surface to its beneficial radiation. Recognizing the seasonal variation in the nature and quantity of insolation, the skin of operable insulated lites is supplemented on the south facade by a system of sunshade louvers. The louvers block the sun during the summer from striking the facade, providing a cooling effect, while allowing it to penetrate in the winter. In both seasons the upper louvers on each floor act as light shelves, bouncing the incident daylight deeper into the interior displacing the need for energy-guzzling artificial light. The lower louvers on each floor are skinned with photovoltaic cells to absorb sunlight, converting it to electricity, and to prevent glare. Water-circulating piping/tubes could be embedded in the louvers as well, enhancing the exchange of heat across the building directly and evening out the temperature differential throughout, from hot zones to cold in the winter and visa versa in the summer, depending on the direction of flow. The north facade in contrast is smooth, shedding wind and weather, and the amount of glazing is artfully diminished without sacrificing light and air to the offices.

The original structural materials and building systems are exposed where appropriate, to emphasize the natural organic performance of the building; this includes cast-in-place concrete columns and cores, mechanical air handling ducts and equipment, and steel ramps, stairs, and guardrails. The upper tower floors holding the offices feature raised computer-floor throughout, while the ceilings are finished with gypsum board “clouds,” suspended beneath a flexible track system that carries lighting, ductwork, and sprinklers. This track system, in combination with a flexible partition system, allows the offices to be reconfigured as future needs require. Complementing the robust functional elements are highly refined sliding glass door and wood veneer partition system, dividing the offices and corridors, and decorative feature panels of wood and stainless steel that dress up the public areas and meeting rooms.

The tower form lends itself to a natural vertical division between the more public spaces toward the base and the private office areas above. Only one level of subterranean parking is proposed, using the basement space already excavated for the existing building (as well as the sub-basement), which reduces the hydrologic difficulties and excavation expense; parking is also distributed on three levels in a plinth above ground. The upper level of this plinth serves as the main meeting area for the company and its guests and division between public and private zones of the building. The Speisesaal and event spaces are located on this level, arranged so that the sheltered outdoor areas of the plinth can be used for daily dining and for special events. Above this level, the next three levels (between the plinth and the typical tower floors) have expanded floor plates due to the rotation of the tower; these levels thus host the larger aggregated program areas, such as server room, training spaces, and call center. These spaces also provide a buffer between the public spaces below and the offices above. The bulk of the tower is made up of eleven repetitive floor plates, with flexible cellular office space arranged around the perimeter. These levels are linked vertically in groups of three by open atria in the central core area, promoting larger workgroup affiliations. The uppermost level serves as the executive area, with access to the roof and helipad.