Awarded with a DGNB platinum certificate, the organic goods trading company Alnatura has a new headquarters in Darmstadt dubbed the "Alnatura Arbeitswelt" (Alnatura employment world) and is raising the bar in the field of sustainable construction. In addition to reusable and previously recycled building materials, environmental friendliness was the main factor in selecting building equipment. The result? Some of the technologies used to ventilate the building naturally year-round are from D+H. The building design does away with climate control and ventilation systems that require a great deal of resources and maintenance. The fire protection strategy for the building also included very stringent safety requirements. D+H served as the SHEV specialist company (smoke and heat exhaust ventilation) throughout the construction project. It provided planning support and an intelligent SHEV controller: the CPS-M digital smoke vent control panel. This panel makes it possible for all components to interact, ensuring preventive fire protection.
The Alnatura Arbeitswelt has a total area of 13,500 square metres, making it the largest European building to feature an outer façade made of clay. The Stuttgart-based architectural firm "haascookzemmrich Studio 2050" put a great deal of thought into the sustainability of the building. And it shows – in several aspects. For example, the project was the first in the world to feature geothermic wall heating. This heating system is located in what are called "rammed earth walls," which are composed of a mixture of gravel, crushed rock, foamed waste glass, clay and the crushed rubble from an old military barracks. The heating coils that these walls are equipped with allow them to serve as a method of heating and as excellent heat accumulators.
The fire protection strategy stipulates a combination of a sprinkler system as well as machine-based and natural smoke extraction
In addition to sustainability, a great deal of value was placed on the safety of the employees working inside the building. "The fire protection strategy for the Alnatura Arbeitswelt is very complex and detailed," says Markus Krause, Property Consultant at D+H Deutschland GmbH. "Just the topics of smoke exhaust and the alarm and control matrix themselves take up nine DIN A4 pages." Krause supported the architects by providing technical SHEV expertise while the tenders were being prepared for the drive and control technology. He also assisted Ingenieurbüro Werner Schwarz GmbH throughout the planning process for the electrical technology as a technical contact partner. The fire protection strategy for the building specified a fundamental combination of natural smoke extraction solutions, sprinkler systems and machine-based smoke extraction. To ensure that the thermal sensors of the sprinkler system did not become ineffective or trip too late, all ventilation openings in the roof area had to close in case of fire. This means that it was established very early on in the planning process that the SHEV and ventilation functions of the roof area window drives had to be technically separate from each other. The fire scenario would ideally start with the activation of the sprinkler system along with the machine-based smoke extraction while smoke levels in the staircase escape routes are simultaneously kept low.
Markus Krause has worked in close collaboration with IB Schwarz and the Stuttgart-based architects to come up with a solution. The resulting call for tenders was won by the D+H partner company "Hübler Sicherheit und Service GmbH." This company served as the specialist company assisting the project heads in implementation. Additional requirements from the fire protection strategy stipulated that the four stairwells in the Alnatura Arbeitswelt be divided into separate fire compartments with their own smoke vent lines. The side-hung windows located there were equipped with the D+H chain drives from the KA Series for supply air. In addition, CDC Series chain drives were installed in the façade of the atrium. For the heavy skylight windows in the atrium roof, the technical planners opted for powerful chain drives from the CDP Series, which are being used exclusively for ventilation purposes here. In addition, pneumatic SHEV solutions were installed in the roof. Like the sprinkler system, they respond to thermal sensors.
Complex fire scenario ensuring safety
Now, as soon as any fire arises in the Alnatura Arbeitswelt, this is what happens: The smoke detectors divided by specific sectors in the building detect the smoke and send a command over the fire alarm system to the CPS-M digital smoke extraction controller located in the central technology room. This controller then executes multiple commands in sequence based on the fire protection strategy. First, the ventilation function of the window drives in the atrium roof is overridden and the windows close in order to reach the trigger temperature of 68 degrees Celsius for the sprinkler system as quickly as possible. The next step is to retract the inner shades located in front of the SHEV flaps – even in the event of a power cut – so that the required smoke-vent areas are not impeded. At the same time, the fire alarm system initiates mechanical smoke extraction in one or more sectors.
The CPS-M SHEV controller starts by opening the supply air openings in the façades of the affected sector. Then, as soon as the OPEN signal is received from the supply air windows, the controller starts the smoke extraction ventilators. According to Markus Krause, it is generally very important that this sequence be adhered to. The reason is because the mechanical smoke extraction systems can create an air flow of up to 40,000 m³ per hour, causing an enormously high negative pressure. "Without sufficient and controlled backflow from outside, the negative pressure inside the building could become strong enough to prevent outward-opening escape doors from being opened." To ensure that the smoke levels in the connected escape routes of the Alnatura Arbeitswelt are kept low, the SHEV openings in the stairwells are opened in case of fire to allow for natural smoke and heat exhaust ventilation. If all these measures fail to prevent a temperature of 141 degrees Celsius inside the building and there is a risk of the mullion and transom construction deforming, pressure cartridges are used for automatic emergency tripping of the pneumatic SHEV systems. According to the fire protection strategy, the CPS-M also offers the option for the fire brigade to use an external control panel to trigger the atrium SHEV system manually at an earlier Point in time.
CPS-M: Compact SHEV controller with a broad spectrum of functions
The CPS-M smart smoke vent control panel from D+H is ideally suited for highly complex structures as well as for the three-story Alnatura Arbeitswelt. This is because it features a modular design and the virtually unlimited power capacity that such a design offers. It vastly increases building safety standards thanks to intelligent networking and is extremely cost-efficient and flexible due to reduced cable routing and its compact design. Thanks to a new module, the "AM230," the CPS-M now features both the 24-volt output as well as a 230-volt output. As a result, it was possible for the CPS-M to actuate both the 24 V drives in the façade and the powerful 230 V drives in the roof. The 230 volt output in the new Alnatura headquarters provided the architects with a great deal of additional advantages. "The high voltage allowed us to greatly reduce the cable cross-sections. That saves raw material," says Sinan Tiryaki, Project Manager Architect from haascookzemmrich Studio 2050. "In addition, this made it possible for us to give the copper cables sufficient covering. Not even the sophisticated roof design gave us problems in terms of structural engineering."
The CPS-M, which is connected to the building management system, handles both the SHEV functions and the natural ventilation commands. The ventilation strategy used here is multi-layered in much the same way as the fire protection strategy. In a pine forest located to the west of the building, there are two intake towers drawing in fresh air and directing it into the building through a ground duct. The air flow is propelled by the thermal updraft in the atrium, which is created due to the openings in the atrium skylight windows. Due to the fact that the soil pre-conditions the air (by warming it in the winter and cooling it in the summer), the additional heating and cooling requirements of the Alnatura campus are very low. As a result, the ventilation strategy fits into the overall environmental concept of the building, which also features advanced smoke extraction solutions that make it extremely safe. "These challenging projects are incredibly fun," says Mato Miskic, Technical Director from Hübler Sicherheit und Service GmbH. "It was specifically the close exchange of design ideas, among all the relevant trades and throughout the project, that led to these tremendous smoke extraction and ventilation results." In recognition of its sustainable architecture and high-performance building equipment, the Alnatura Arbeitswelt was presented with the DGNB Platinum Certificate (German Sustainable Building Council).