Controlled consumption

The headquarters of the Deutsche Bank in Frankfurt has undergone a complete transformation, cutting its energy requirements in half and CO₂ emissions by almost 90 per cent. Amanda Allen talks to Wilfried Kramb of lighting designers a•g Licht about this unique office space

The twin towers of the Deutsche Bank headquarters in Frankfurt act as a landmark for the financial centre of the city. Standing 155m high and referred to as ‘debit’ and ‘credit’, the towers have undergone a radical renovation since 2007, and in the process have squared the company’s account with the environment.

The ‘green’ elements of the building are numerous and in recognition of the approach taken during its renovation, and the consequent reductions in the consumption of CO₂ and energy, the building achieved LEED Platinum certification by the US Green Building Council, as well as DGNB Gold by the German Sustainable Building Council.

The dual objectives of high-end design and absolute efficiency presented the crux of the design challenge for the lighting designers. “The brief was a combination of guaranteed function and energy efficiency,” says Wilfried Kramb of a•g Licht.

Public space

The entire ground floor area of the building is accessible to the public and contains a new branch of the bank, a business centre and a public forum for the bank’s brand. In this area, the focus is very much on a 16m-diameter spectacular sphere enhanced with accentuated light. Made using untreated steel bands and floating in the air space of the foyer, the sphere is pierced by two backlit bridges that connect the two towers.

The bridges are backlit using a double row of T5 fluorescent battens. The use of both artificial and natural light in this area was key, according to Kramb. “The spotlighting of the sphere was very important. It’s being spotlighted from the top using narrow-beam metal halide spotlights with black cross louvers, creating a highlight on the sphere which shows it as an individual element and we used a neutral white light to create a warmer colour in the area.”

The second element at play in the foyer is what the designers call the ‘honeycomb façade’. The façade is made of glass, with an integrated aluminium honeycomb structure and backlit with daylight white LEDs within a custom made profile system. “The façade was developed by the architects in cooperation with us,” explains Kramb, “They wanted to create a screen-like structure that would give the lobby a uniform look. It veils the activity behind but you still have a sense of what is going on in each area.”

Official business

Of course office lighting is not just about elaborate, public-facing areas. Over 90 per cent of the Deutsche Bank building comprises of open-plan work areas and cellular offices separated by glass partitions. In these areas a•g Licht worked to achieve the most energy efficient model which meant they could incorporate more elaborate lighting solutions in the remaining 10 per cent of the building. “This ultra efficient approach to such a large proportion of the building allowed us to incorporate additional lighting solutions in the remaining areas of the building, including backlit handrails in the foyer and more bespoke solutions for the conference rooms,” says Kramb.

For the office space a special sword-shaped luminaire was purpose-designed by a•g Licht. With the design in mind a•g Licht and the Deutsche Bank challenged different manufacturers to produce what they wanted, with Zumtobel emerging victorious. “Our design offered a high output of light in comparison with the energy consumed and, essentially for us, when the luminaire is lit you can’t see it, all you see is the light itself,” says Kramb.

The luminaires are fixed to the ceiling compartments making them more favourable than a conventional solution. “One of the overall objectives of the building was to have a higher ceiling level than they had before. If we had gone for a pendent light we would have, at least psychologically, lowered the ceiling,” says Kramb.

The luminaire uses a T5 35W or 28W fluorescent lamp and has a light output ratio of 84 per cent. The light is mainly directed downwards, but some of it is also directed upwards to illuminate the ceiling.

Needs must

While efficiency was achieved to a certain degree through the development of the sword-shaped luminaires, an integral part of the savings made came from the lighting control systems. Overall lux levels in the office are at 300 and task lighting allows for each individual work space to be increased to 500 lux where necessary. In archive areas lux levels drop to 200-250 and drop further again to 100-150 in the walkways.

The building incorporates light systems that can be controlled individually in certain areas and presence detectors mean that light is only used in areas of activity. “This not only applies in meeting rooms but is also effective in open office spaces within the building. If a group of people are working in a small section of a large area, only that section will be illuminated, which can be very effective at holiday times,” says Kramb.

The light systems are also linked to the amount of daylight in the building so the lowest possible energy is used in relation to the daylight available. “If daylight is present and providing the 300 lux, then no fixtures will be switched on.

As soon as the levels of natural light fall below 300 lux, the lights will come on to make up the shortfall,” says Kramb.

Conference call

Such parsimony in the rest of the building allowed the lighting designers to be more elaborate with their designs in the conference and meeting rooms. In the meeting rooms, ceiling sails were integrated with Zumtobel Slotlight II LED light lines and1.2W LEDs with a 3000k colour temperature were used. “To have a different quality here we also added some halogen downlighting, to add some warmth to the area. Conference areas need a different atmosphere from the standard office and for video conferencing we could achieve the highest colour rendition with the halogen. Because only the minimum energy was used in the majority of the building we still didn’t exceed with our watts per square metre in the main areas of the building,” says Kramb.

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