Fennia office building, Helsinki

fennia 800Project facts

Type: Office, detailed studies
Consultant: EQUA
Client:Are Oy
Summary: Retrofit of office building with high U-values. Ceiling heating/cooling panels, integrated to Sensus-system, were carefully dimensioned and positioned, resulting in good comfort and 25-35 % energy savings compared to tradition system.


The aim of the study was use radiant ceiling heating/cooling panels in a renovation project with relative high window and envelope constructions U-values. The ceiling panels were integrated to Sensus-system, which is developed by Are (one of the biggest HVAC contractors in Finland). The system suitability and possible energy savings were explored for system decision making.
In the Sensus-system the internal heat gains from the water based cooling panel network are used in AHU supply air heating with simultaneous free cooling effect to zones.
The system is controlled with developed special automation system with several control circuits and valves.
The challenge was to get comfort summer and winter time indoor conditions with none replaced windows (U=2.0 W/m2K, g-value 0.62) and fair and reliable energy use comparison between traditional system and Sensus.
More information about Sensus system


Special attention and care with heating/cooling panel sizing, panel positions in spaces and optimal panel surface area in order to fulfil indoor climate requirements. Avoiding extra costs of studied system with precise component dimensions and careful load simulations against manufacturer design data.

fennia solution

Modeled office building floor and nearest surrounding buildings causing shading to windows

fennia plant

Plant general view. Pipe connections were done with PMTMUX-objects within special macro

The energy savings were achieved mainly by the following improvements compared to the traditional system:

  • Optimal free cooling with simultaneous heating to supply air from internal gains
  • Optimal night ventilation/free cooling/night cooling usage
  • CO2- and temperature based demand ventilation. In temperature based control the free cooling via cooling panels was used before the VAV control to get optimal energy use
  • Using night setback with variable heating setpoints and effective morning warmup


By proper dimensioning the required indoor climate conditions were fulfilled with the studied heating/cooling panel system. At some locations of the building with high windows water radiators were used instead/additionally with the panels, because of the high heating need. Water radiator network was already used/present because of secondary space use, so there was an existing network to connect the radiators.

Compared to traditional system Sensus system gave:

  • 25 % computational heating energy savings (in simulated office (only) spaces calculated without the DHW usage)
  • And concerning the same simulated spaces 35 % computational energy savings in district cooling energy

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