In Lahti, even small renovations reduce emissions and improve energy efficiency

News 2022-08-04 at 10:01
Lehtioja service center © Lahden Talot Oy.

In the last year, renovations have been carried out in Lahti to improve energy efficiency and reduce emissions. This is a project of the City of Lahti and Lahden Talot Oy, where seven residential properties are renovated.

At the beginning of the project, seven future renovation sites were selected, which have already previously accurately measured energy consumption. In this case, the effects of the measures taken on emissions, energy consumption and costs can be calculated after the completion of the renovations.

Data on the renovations will be collected for about a year, after which material will be compiled from the calculations for Lahden Talot and for distribution to other property owners. “During the autumn of 2021, we completed six renovations, and we have started to prepare the material for distribution,” says Project Manager Pauli Piekkari from the City of Lahti. “The material to be produced shall be in an easily understandable form, such as short informational videos.”

Based on the shared material, Lahden Talot and other property owners can utilise the results in their own renovations, which multiplies the positive effects.

New and different measures are being tried out with renovations

Thanks to specific individual measures, it is possible to measure the real impact of these measures. “It is easy to make calculations for even larger renovations, but it is usually difficult to measure the impact of an individual measure afterwards,” Piekkari says.

Three of the renovations focus on heating control, one on the air heat water pump, one on water saving, one on the replacement of air conditioning exhaust fans and one on the recovery of wastewater heat.

“We get to try out interesting and less frequently used measures in the project,” Piekkari comments. For example, wastewater heat recovery is not yet widely used in residential buildings. However, in other types of sites, such as swimming pools, the heat loss of wastewater is already being harnessed.

Wastewater heat recovery addresses heat loss

The renovation, which enables the recovery of wastewater heat, was carried out about a year ago and was the largest in financial terms. However, the renovation has significant benefits, as the heat loss of wastewater is typically high, especially in residential apartment buildings.

The renovation was carried out in an assisted living building consisting of 190 apartments. The assisted living building was chosen because the consumption of water in such a property is high, which also emphasises the heat loss of wastewater.

The wastewater heat recovery system was built as part of the geothermal system in the property, which means that by connecting the heat exchanger as part of the system, the existing system will be able to pump heat from wastewater.

After the renovation, the temperature of the geothermal heat collection circuit is higher and the geothermal heating pumps therefore operate with better efficiency, consume less electricity and thus also produce less emissions. If the wastewater heat recovery system were to be included already at the planning stage of the geothermal system, some fewer heat wells could be implemented, which would affect the space requirements and costs of the wells during the construction phase.

The system is dimensioned so that at least half of the heat loss of the wastewater is recovered. According to the calculations, the heat energy collected is predicted to be 90 megawatt hours and carbon dioxide emissions to be reduced by 11.2 tonnes per year.

“The Canemure project supports the long-term environmental work of Lahden Talot to reduce carbon dioxide emissions. The project allowed us to pilot various solutions that support energy saving. We hope that the project and its results will also help other sites/municipalities where measures to reduce carbon dioxide emissions are planned,” says Environment Manager Elina Rantanen from the Lahden Talot.

Learn more

Further information

  • environmental coordinator Jenni Rahkonen, City of Lahti,, tel. +358 44 4826646
  • environment manager Elina Rantanen, Lahden Talot,, tel. +358 (0)3 851 570

  • Print page