During the first years of operation, the building was monitored closely. This allowed energy consumption and factors affecting it to be observed precisely and attention was also drawn to incorrect settings and difficulties with control technology. At first, e.g. the ventilation devices ran with high supply air temperatures, unnoticed by staff. Prompt evaluation of the measurement data discovered the increased energy consumption. The annual coefficient of performance of the heat pump was approx. 3.1 in 2003. Regulation via reference rooms led to uneven temperature distribution and unnecessary pump running times due to unexpected staff absences or larger numbers of people working in the reference rooms.

At the end of 2004, the system was switched over to demand-oriented control. At the same time, the supply temperature was lowered. Now, the pump is turned on and off depending on ΔT between supply and return temperature. The energy requirement control system was developed especially for this building was difficult to adjust, especially in the beginning. The best time periods for measuring had to be determined empirically. Today, the control system is mature and there is a relatively large time period when no heating or cooling is demanded, i.e. when the heat pump is switched off. The supply temperatures were also reduced further. The annual coefficient of performance thus improved to 4.3 (2007).

The decision concerning the ventilation to only let in low amount of fresh air has proved to be practicable . Measurements showed that the CO2 concentration remains considerably below the maximum amount recommended for the workplace. Even with very low or high outside temperatures, longer window ventilation also had little effect on thermal comfort. The ventilation system’s heat exchanger reaches an efficiency of up to 75%. Since the air ducts are not insulated and run partly within the CCTC ceiling, the supply air also adopts the temperature of the room or ceiling. Therefore the additional temperature control function of the supply air with the borehole heat exchangers was shut down. Specific electricity consumption for the ventilation constantly rose for all floors but by different amounts. On the one hand, due to high numbers of staff present at the same time and frequent occupancy in some offices the amounts of air required are larger than expected. On the other hand, the ventilation is often adjusted “by hand” and not changed back later.
Despite there being solely internal shading without any solar protection glass, according to statements of the users, the interior climate was satisfactory even in the extremely hot summer of 2003. Effective cooling by the CCTC no doubt contributed to this. Measurements in south-facing offices established that there were up to 214 hours with air temperatures above 26°C during working hours in 2006.

Electricity consumption for lighting (without table lights) was close to the planned value of 10 kWh/m² p.a. Dark floors, less transparent interior walls, workplaces located away from the windows or shade from neighbouring buildings constituted the reason for the increased consumption in individual office units. Initially in 2005, daylight control was only used on the 2nd floor and extended to the whole building in 2006.