Fennia Office Building, Helsinki


fennia 800

Project Information:

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


The aim of the study was to use radiant ceiling heating/cooling panels in a renovation project with relative high window and envelope construction U-values. The ceiling panels were integrated to the Sensus-system, which is developed by Are - one of the largest HVAC (Heating, Ventilation and Cooling) contractors in Finland. The system suitability and possible energy savings were explored to calculate effective results.
In the Sensus-system the internal heat gains from the water based cooling panel network are used in AHU (Air Handling Unit) 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 attain 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 comparisons between the traditional system and Sensus.

Read 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 additional costs of a 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


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 (Variable Air Volume) control to attain optimal energy usage
  • Using night setback with variable heating setpoints and effective morning warmup



Proper dimensioning of the required indoor climate conditions were fulfilled with the studied heating/cooling panel system. Because of the high heating needs, at some locations of the building with high windows, water radiators were used instead/additionally with the panels. The 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 provided:

  • 25% computational heating energy savings in simulated office (only) spaces calculated without the DHW (Domestic Hot Water) usage
  • Regarding the same simulated spaces - 35% computational energy savings in district cooling energy

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