The award-winning PLATINUM Wiesbaden is a flagship project for sustainable building standards, user comfort and future-oriented architecture. Kiefer Klimatechnik was responsible for the planning and installation of the complex ventilation and air-conditioning system. In addition, Kiefer's INDUL linear diffusers ensure excellent thermal comfort and outstanding indoor air quality. Their performance was verified by our HVAC experts in Kiefer's own airflow laboratory by means of extensive airflow simulations and room airflow measurements.
 

Designed by Neumann Architekten (Frankfurt) and developed by OFB Projektentwicklung, the timber-hybrid office building demonstrates how sustainable and energy-efficient construction can be successfully realized today. Compared with a conventionally constructed office building, the headquarters of Hessen Agentur GmbH reduces annual CO₂ emissions by approximately 1,160 tonnes.
Together with an innovative building energy concept, the building generates more renewable energy over the course of a year than it consumes during operation. This is achieved by approximately 1,300 m² of photovoltaic panels installed on the roof and façade, generating around 150 MWh of electricity per year, as well as an underground 400 m³ ice storage system with a storage capacity of 32,275 kWh for heating and cooling.
For its outstanding sustainability concept, PLATINUM Wiesbaden received the DGNB Platinum Certificate, the highest award of the German Sustainable Building Council.
 

Kiefer Klimatechnik, based in Stuttgart, was responsible for the planning and installation of the complete ventilation and air-conditioning system. The system consists of two central air handling units (AHUs) installed in the basement and on the fifth floor, supplying different areas of the building. The basement unit exclusively serves the lower floor, while the second AHU provides ventilation and air conditioning for all office and sanitary areas above ground.
Outside air is drawn in through the façade, efficiently treated and conditioned in the AHU. Integrated heat recovery combined with adiabatic cooling (evaporative cooling) ensures sustainable and energy-efficient temperature control. The conditioned supply air is then introduced into the offices and meeting rooms via INDUL linear diffusers, providing draught-free air distribution and excellent thermal comfort.

With a total volume flow rate of approximately 16,300 m³/h, PLATINUM Wiesbaden relies on an intelligent variable air volume (VAV) system. Integrated indoor air quality sensors continuously monitor room conditions and automatically adjust the supply air volume according to demand. In the office areas, air exchange rates range from 1.0 to 1.8 h⁻¹. When conference rooms are fully occupied, the system immediately increases the air exchange rate to 6.0 h⁻¹, while reducing the supply air volume in less frequently occupied office areas to maximise energy efficiency.
 

Extract air from the office areas is transferred into the corridors via INDUSILENT transfer grilles, where it is extracted centrally. These highly effective acoustic components provide excellent sound absorption while reliably preventing speech transmission between adjacent rooms—creating ideal conditions for concentrated work and a pleasant, discreet working environment.

The client and consulting engineers had equally high expectations for the indoor climate concept. Through the close cooperation between Kiefer's component and product development teams, these requirements were not only fulfilled but exceeded with the installation of INDUL linear diffusers. Daniel Nack, Head of Development at Kiefer Klimatechnik, explains: "The objective was to verify in advance whether, and to what extent, the slot diffuser would meet the thermal comfort requirements particularly during summer operation—under these special installation conditions." The diffusers were installed in the ceiling area adjacent to the façade glazing. This resulted in an asymmetrical free jet characteristic towards the occupied space, influencing both the room airflow pattern and the resulting thermal comfort. At the same time, the surface and radiant temperatures of the surrounding building envelope had to be considered during the design phase.

One of the key characteristics of the INDUL linear diffuser is its exceptionally high induction. Fine individual air jets rapidly mix supply air with ambient air, quickly reducing both temperature differentials and air velocities before the airflow reaches the occupied zone. This ensures draught-free air distribution and excellent thermal comfort. The slim diffuser profiles also integrate almost invisibly into the modern ceiling architecture.

In Kiefer's in-house room airflow laboratory at the Development Centre, room airflow measurements, acoustic measurements and optimisations can be carried out quickly and efficiently under realistic operating conditions. For this project, Kiefer's engineers investigated the INDUL linear diffuser by means of extensive room airflow measurements to evaluate its free jet characteristics and the resulting room airflow pattern. In addition, the three-dimensional airflow was visualised using white smoke tracer.
The local thermal comfort was also assessed in accordance with DIN EN ISO 7730 under both full-load cooling and reduced operating conditions. The evaluation was based on a seated person (1.2 met = 58.2 W/m²), wearing typical summer clothing (0.5 clo = 0.080 m²K/W), with a relative humidity of approximately 50%.
To reproduce the real installation conditions, a representative section of an open-plan office from PLATINUM Wiesbaden was recreated in the laboratory, including simulated occupant and equipment heat loads. An 800 mm INDUL linear diffuser with an asymmetrical free jet characteristic was installed and adjusted to the specified operating parameters.

During the subsequent test series, a dedicated measuring system recorded all parameters required to evaluate thermal comfort at 20 measuring points located at head (standing and seated), knee and foot level. These included local air velocity, local air temperature and the calculated draught rate. Measurements were carried out under both full-load cooling with a volume flow rate of 45 m³/h and reduced operation with 25 m³/h, each with a temperature differential between supply air and room air of ΔT = –6 K.

The results confirmed that the INDUL linear diffuser achieved a uniform and optimised room airflow pattern, regardless of the selected volume flow rate. Owing to its high induction, temperature differentials and air velocities were effectively reduced before the supply air entered the occupied zone. The supply air was distributed evenly throughout the room, both horizontally and vertically, ensuring draught-free air distribution without causing local discomfort such as draught sensation or cold feet.
The room airflow measurements demonstrated that Thermal Comfort Category A in accordance with DIN EN 16798-1 was achieved in all assessment criteria.

These convincing results also impressed the client and consulting engineers, leading to the installation of approximately 350 linear metres of INDUL linear diffusers throughout the building's five office floors. More than three years after completion, user feedback remains consistently positive. As Folke Mühlhölzer, Chairman of the Management Board of Hessen Agentur, explains:
“The ventilation system fully meets our expectations for excellent indoor air quality. It operates virtually silently, there are no draughts, and we even have the impression that less dust and pollen enter the building.”