A housing association in Helsinki switched to renewable energy

Property manager Petri Kukkonen: “This is the set with which savings are made.”

The apartment building housing association located in Helsinki’s Lehtisaari switched from district heating to a hybrid system that utilizes renewable energy. The innovative system combining geothermal heat, heat recovery and solar electricity brings significant savings and self-sufficiency to As Oy Lehtisaari Salpa. The equipment was supplied by Gebwell and the contract was executed by Tom Allen Senera.

As Oy Lehtisaari Salpa’s six apartment buildings were built in Helsinki’s Lehtisaari in the 1960s.


The biggest savings with a hybrid system

The energy renovation of the housing association of six apartment buildings was proposed by property manager Petri Kukkonen. The goal of the renovation was to save on heating costs and to get rid of district heating, the price of which was rising.

During the project, Paavo Viitamäki was the chairman of the board of the housing company. “We wanted to heat more efficiently with advanced geothermal technology and utilize the waste heat of the exhaust air,” he says.

The calculations showed that the best savings would be brought by a hybrid system, where geothermal heat and exhaust air heat recovery are supplemented by a solar power plant. “The euro flashes in their mind, and this is the whole with which savings are made,” says Petri Kukkonen. According to preliminary estimates, two-thirds of the heating costs can be eliminated with the new system.

The building company’s wishes were taken into account in the offer

The building company tendered two contractors, of which Tom Allen Senera’s bid won. Based on the contractor’s suggestion, Gebwell heat pumps and hot water heaters were chosen for the new system. “We trusted that the equipment proposed by the contractor was good, and the fact that the manufacturer was domestic was a clear plus,” says Viitamäki.

Gebwell’s geothermal heat pumps and accumulators were installed in an old, renovated technical space.

Eight Gebwell geothermal heat pumps were installed in the utility room.

Energy efficiency with building automation

The parts of the hybrid system work together under the control of the building automation application. When the solar power plant produces more electricity than the property’s total consumption, the automation directs the surplus electricity to heating the hot domestic water.

The heat is collected from the exhaust air by heat recovery units on the roofs of the apartment buildings and directed back to the heat pumps. Waste heat can be stored in warm weather in energy wells drilled into the ground. “It’s not a bad idea to pump the heat underground,” says Paavo Viitamäki.

Based on metrics that monitor energy consumption and yield, the automation guides the utilization of excess solar electricity.

Self-sufficiency from renewable energy

The system has worked as expected since the start-up. “There is enough heat, and the difference to the previous system is not noticeable,” says Paavo Viitamäki. According to Viitamäki, the advantage of the system is also energy self-sufficiency.

Petri Kukkonen and Paavo Viitamäki are satisfied with the contract and can recommend a similar system with equipment to others.

As Oy Lehtisaari’s Salpa hybrid system

  • A housing association of six apartment buildings
  • 168 apartments
  • Years of construction: 1967–1968
  • Installed heat pumps: 8 Gebwell Taurus 110 EVI
  • 36 energy wells, depth 300 m each
  • Heating costs with district heating: approx. 305,400 e/year
  • Heating costs with geothermal, exhaust air heat recovery and solar electricity: approx. 82,710 e/year
  • Savings in heating costs approx. 222,690 e/year (73%)