THE multi-floor In the Bow

Detailed planning

The ClimaLevel Multiboden will play an important role in creating maximum thermal comfort in Freiburg’s flagship project The Bow.

The planning process
With Multiboden, the screed mass is used thermally.
As with conventional underfloor heating, the screed is heated or cooled through plastic pipes.
The supply air to the offices flows through the hollow floor below the thermally active screed.
Which planning parameters must be observed?

Heat output
The basis is the heat load calculation.
Based on this, a design is made in accordance with EN 1264, analogous to a conventional underfloor heating system.
If we make the simplifying assumption that the system-integrated supply air supply is isothermal (supply air temperature = room air temperature), then it is completely sufficient if the floor is designed purely for the transmission heat requirement.
However, the system hydraulics with the mass flow of the heating or cooling water in The Bow project is determined by the desired cooling capacity.

Cooling capacity
Of course, conventional underfloor heating systems can also be used to cool buildings.
However, as the convective heat transfer between the floor and room air decreases rapidly when cooling, the specific cooling capacity of pure underfloor cooling is only 20 to 30 W/m2.
The ClimaLevel Multiboden increases the cooling capacity primarily through the type of supply air inflow.
The conditioned outside air flows draught-free into the room through floor air outlets and stimulates convective heat transfer.
The cooling capacity of the floor thus achieves Values of over 50 W^/m2.

System hydraulics
For optimum cooling performance, the ClimaLevel multi-floor in this project is set to tv = 16 °C and tr = 19 °C designed.
The spread is therefore only 3K.
The pumps and the pipe network must then be designed accordingly. To ensure stable system hydraulics, each manifold is equipped with a differential pressure regulator.

Supply air volume flows
The multi-floor is usually operated with 100 percent outside air.
The ventilation system is therefore dimensioned according to the personal outdoor air rate per room.
For The Bow, this is 40 m3/h person.
As the cooling capacity of the system only depends to a small extent on the supply air introduced and its temperature, this results in a very economical system design with significantly lower air volumes than with pure air cooling.

Air outlets
The supply air flows into the room via floor-integrated air outlets.
The stainless steel LLE diffusers used are a joint development between ClimaLevel Energiesysteme and Krantz Komponenten from Aachen.
The aim of the diffuser characteristics is to create turbulent mixed ventilation without draughts.
The LLE diffusers have a uniform slot width of 3 mm and 1 to 4 rows of slots.
The choice of diffusers depends on the determined volume flow and the room height.

Dehumidification of the supply air
If ambitious demands are placed on the cooling capacity of the system, the supply air must be dehumidified in the central air unit.
The required dehumidification capacity must be taken into account when dimensioning the cooling aggregate must be taken into account.

Floor structure
To accommodate the desired underfloor cabling in the floor, The Bow uses the multi-floor construction variant III.
The installation height including screed is 200 mm. The first level, which is laid on the unfinished floor, contains the underfloor cabling together with floor sockets to accommodate the electricians and floor sockets later on.
As the system is naturally not as flexible as a classic raised floor, routes and possible positioning of sockets must be coordinated in advance.