The planned repurposing of the computing centre of Neckermann Versand AG, built in the 70's as a concrete-skeleton building with natural stone facade, tiltable metal windows and a central air conditioning system, raised the question of technically and economically optimal air conditioning. With old buildings, it's not unusual to have energy savings considerations, which tend away from central air conditioning systems towards decentralized ventilation systems. Architects, too, increasingly favor decentralized air conditioning and/or air conditioning designs in which the whole system is integrated inconspicuously into the window frames or double flooring.
Conventionally air-conditioned office buildings from the 70's and 80's often truly act as energy centrifuges and force reorganization-minded owners to look for economical alternatives. A systems comparison with dynamic building simulations showed substantial advantages for an exhaust air facade with axially situated air conditioning devices. Finally, the decisive factor in choice of a system was the owner's requirement to reorganize the building floor-by-floor without interrupting ongoing business.

Consistent with the task, construction in the Neckermann building commenced with decentralized undersill ventilation from the company Fassaden-System-Lueftung (FSL): Beginning on the upper floors, two floors at a time were reorganized, and then the departments under them moved up into the finished floors. External air intakes and internal air circulation devices were alternated. Via an opening on the facade and a filter, the external air intakes suck in fresh air, then warm it or cool it according to weather and need. The exhaust air is then directed from the ceiling over the whole window surface downward into the equipment, passing through a heat recovery device before it is ejected to the outside.
The relatively warm exhaust air current improves the insulation of the building and gives part of its energy to the incoming external air in the heat recovery unit. Air currents are similar in the air conditioning units, except that the external air part and the heat recovery unit are omitted. Flow rates are regulated automatically by air quality sensors in the offices. Ambient temperature regulation can be locked with priority function. Furthermore, the whole system can be used for cooling of building zones by "pre-cooling" the building with pure outside air outside working hours – mainly at night.