New administration building SWBB headquarters, Böblingen (BW)

Initial situation

The area surrounding the building site is heterogeneous, characterized by residential buildings of varying density (including 16-story high-rises) and scattered commercial buildings to the north and west, as well as public buildings such as schools, kindergartens, and sports facilities to the east. To the south lie wooded areas, and further south is the SWBB operations center with its combined heat and power plant and water supply.

Urban planning concept

The building mass of the planned new building is based in size on the existing administration building and is proposed as a spatial boundary by means of perimeter development to the north of the existing administration building.

Urban structure / building structure

The eastern edge of the planned new building aligns with the edge of the existing administration building. With its four-story facade facing Ernst-Reuter-Straße, the building creates a visually calm and uncluttered conclusion to the site. To utilize the existing, staggered parking deck on the ground floor, the main entrance of the new building was recessed and simultaneously covered. This allows for clear and familiar access while requiring virtually no modifications to the existing parking deck and underground garage (thus ensuring cost-effectiveness). The upper floor cantilevers freely in this area, lending the main entrance a prestigious appearance. The planned new building stands completely freestanding (soundproofed). Two accessible parking spaces are provided under the canopy. The building features a sloping facade facing west, both to maximize natural light and to respect the natural character of the adjacent buildings. Furthermore, it gives the building facade, which is more visible from Ernst-Reuter-Straße (the main entrance), a futuristic and impressive appearance. Here, both on the "green balconies" of the individual floors and "under the trees," are the outdoor areas for employee relaxation.

Development

Due to its use, the area cannot generally be kept car-free. However, with regard to the planned new building, the clear objective was to consolidate all car traffic and make sensible use of existing access roads. Access to the facility is primarily via Ernst-Reuter-Straße, as well as on foot or by bicycle via a forest path leading up to the Diezenhalde residential area. Access within the company premises has not been changed. The main entrance of the planned new building is located directly opposite the main entrance of the existing administration building. Directly next to the main entrance are now two disabled parking spaces, as well as the existing customer and employee parking spaces. Parking spaces (cars and bicycles) located in the basement/underground level can be accessed via Ernst-Reuter-Straße (north). The existing storage area for tall goods will be reorganized accordingly; a suitable space should be found in the southwestern part of the depot.

Building

The building has five stories. All floors are organized as a double-loaded corridor. On the ground floor, in addition to the main entrance, there is a foyer, offices, and two meeting rooms, each accommodating 20 people or 40 people when combined. The meeting rooms face the public street, symbolizing accessibility and transparency. Restrooms (including an accessible toilet) and a kitchenette are also located in a block, vertically stacked within the building. The upper floors contain offices with ancillary facilities, as well as break and quiet areas. A distinctive feature of the building is its spacious work areas, which offer both opportunities for interaction and quiet zones. All of these areas are connected to green spaces. On the ground floor, the outdoor area is complemented by a landscaped staircase that provides access to the garden (seating "under the trees"). This staircase also serves as a secondary escape route. The south-facing offices feature floor-to-ceiling glazing (post and beam) with closed window sashes/panels, intended, among other things, to emphasize the visual connection between the existing building and the planned new construction. North-facing offices also have above-average glazing; the window elements (framed windows) have projections and recesses, which, together with the building's defining metal facade, creates a varied and dynamic appearance (play of light and shadow).

Office type:
Cell offices (single and multi-person offices with a focus on multi-person offices).

Grid structure/expansion:
The facade or axis grid was chosen to be 1.40 m.

Green roofs:
Extensive green roof, substrate layer > 10 cm

Photovoltaic system:
Photovoltaic system (approx. 150 m²), electricity generated is fed into the grid.

Barrier-free construction:
The planned building is designed to be barrier-free according to DIN 18040-1.

Statics

Support system:
The planned new building is designed as a solid construction. The building is braced by the stairwell and elevator core. The upper floors will be constructed using a reinforced concrete frame, ensuring greater transparency on these floors. All load-bearing walls are planned as reinforced concrete. Wall thicknesses range from 20 to 30 cm, and column diameters from 30 to 45 cm. Floor slabs are generally designed as flat slabs with a thickness of 35 cm. Ceiling beams will be incorporated as required by structural analysis.

Founding:
Shallow foundations with local reinforcements under the columns and walls. Precise design will be determined during further planning in consultation with the geologist.

Building materials:
All structural components are constructed of reinforced concrete. Concrete grade C25/30 is specified for ceilings, beams, and walls; columns and precast elements are made of higher grade concrete.

Manufacturing process:
The planned new building is largely to be constructed using cast-in-place concrete. The stairwell core can be constructed from prefabricated reinforced concrete hollow walls with a cast-in-place concrete core, thus enabling economical construction and accelerating the construction time.

Building physics:

Reinforced concrete walls (exposed concrete where visible) with MF insulation, d= 30 cm.

North facade:
Aluminum framed windows, e.g. Schüco/AWS 90.SI+ (passive house certified)

South facade:
Aluminum post and beam facade, e.g. Schüco/FWS 50.SI (passive house certified)

Metal facade:
Aluminium composite panel, e.g. Alucobond A2 600 Sunrise Silver Metallic, suspended and ventilated

Energy concept

The aim is to achieve an energy-saving and climate-friendly combination of ecological and economic sustainability in construction. This is to be achieved, among other things, through:

– Avoidance of transport of building materials and components
– Durability of building materials and components (e.g., MF insulation instead of EPS insulation)
– CO2 accounting (e.g., consulting during the preliminary/construction phase by service providers)
– CO2-neutral concept
– Passive House (with certification); DGNB certification (Platinum, at least Gold)
– Energy monitoring and operational optimization

Active systems:
– Heating via district heating (primary energy factor of fp, FW= 0.00; SWBB)
– Photovoltaics (PV) for generating primary energy (electricity) for a net-positive energy house
– Concrete core activation (cooling/heating)
– Ventilation system for replacing stale office air by supplying pre-tempered fresh air with heat recovery (HRV)
– Mechanical ventilation for hygienic minimum air exchange with heat recovery

Passive elements:
– High levels of daylight through floor-to-ceiling windows (south and west facing)
– Natural ventilation of the stairwell (chimney effect)
– Storage mass (exposed concrete ceilings mostly without suspended ceilings)
– Sun protection (outside blinds, inside glare protection)

Building shape and orientation:
– A/V ratio (compact design)
– Building materials
– Solar heat gains in winter vs. solar heat loads in summer

Electric

– Efficient artificial lighting (LED); workplaces using floor lamps
– Structured cabling below raised floor, LAN cabling, lightning protection
– EMA system, access authorization
– Automatic presence detector
– Control of daylight entry (switching lights on/off)

Fire protection

– Required stairwell
– Comprehensive fire alarm system (FAS)
– Two structurally separate escape routes, plus escape windows (emergency repatriation)
– Escape route widths and emergency exits according to legal requirements

open space

On the "green balconies," as well as under the trees bordering the western side, employees will be offered areas for relaxation during breaks or spontaneously. The property will be visually enclosed along Ernst-Reuter-Straße as much as possible by planned, densely growing hedges. Container plantings, for example, are conceivable for the balconies.

Efficiency and flexibility

Economy:
The proposed energy concept, utilizing alternative energy sources, intelligent heating and cooling systems, optimized glazing, and the building's excellent insulation standard, minimizes operating costs. The placement of the building services center and vertical risers is designed to minimize the length of building services pipe runs. The proposed thermally activated building system supports the building's economical operation. The 1.40 m facade and interior grid allows for the use of standardized components. The structural grid of the concrete frame was chosen based on economic considerations. The selected reinforced concrete frame construction, lightweight partition walls, and raised access floors facilitate easy reconfiguration of the office layouts and adaptation to changing usage requirements.

Flexibility:
The building's floor plan grid is designed to accommodate all possible office layouts and uses (combined offices, open-plan offices, group offices, cellular offices, and combinations thereof) with varying usable floor areas. Additionally, ceiling sections are structurally pre-configured to allow for the subsequent installation of internal vertical connections between two floor slabs. The stairwell, with its adjacent access vestibule on the ground floor, offers the possibility, with appropriate partitioning, of creating up to three separate office units with their own access on each floor.