A housing company in Vantaa, Finland achieved an exceptional coefficient of performance by combining ground source heating with heat recovery. Oilon supplied the ground source heat pump system for the project. 

The three apartment buildings operated by housing company Myyrinkoivun talot in Vantaa, Finland look just like normal apartment blocks from the late 70s. What you cannot see from the outside is that their best-in-class energy efficiency. The buildings utilize a ground source heating system with an exceptionally high coefficient of performance (COP). In normal operation, the COP is nearly 4.3; with auxiliary electric heating powered on, it is still as high as 4.

“COP measures the amount of heating provided by a ground source heating system per unit of electricity used. In this case, one kW of electricity used by the heat pump provides more than 4 kW of heating energy. A typical COP is around 3.5. This was the best COP we’ve ever achieved,” says Jarkko Hakonen, who works as a heating expert at Suomen Kiinteistölämpö Oy. 

“On top of the savings generated by transitioning to ground source heating, heat recovery will generate annual savings of EUR 9,000 for the housing company,” Hakonen estimates.

Recovering waste heat from exhaust air

What did it take to reach such high numbers? In October 2021, the housing company completed an extensive overhaul of the building’s HVAC and electrical system. As part of the project, the company transitioned from district heating to ground source heating and had an exhaust air heat recovery system installed. This system captures thermal energy from exhaust air, cooling it down from 21 °C to 5 °C. The recovered heat is channeled to the ground source heat pump’s circulation. 

“Exhaust air recovery systems are not very common; they are, of course, an additional expense, and not always worth the effort to install. Not all properties we renovate are suitable for heat recovery, but in this case, it was a smart option, and the system is quickly paying for itself,” Hakonen says. 

There are two major factors that influence a ground source heating system’s COP: the temperature of the brine supplied to the heat pump and the water temperature that the heat pump needs to produce. 

“In this project, the balance between these two factors was spot on: we could use heat recovery to raise the brine temperature, and, on the other hand, the building has excellent insulation, which means that the heating water doesn’t need to be that hot.” 

Oilon supplied all the equipment used in the Myyrinkoivu heating system. The delivery included three RE 96 heat pumps with a 96-kW capacity, two 1,600-liter DHW tanks, one 1,600-liter heating buffer with a DHW preheating coil as well as a 150-kW electric boiler. 

“Reaching such a high COP would be impossible without high-quality equipment. Oilon’s products are dependable, they have excellent operational reliability, and they require practically zero maintenance. And, from our standpoint, it’s of course easier to order all the equipment you need from one place,” Hakonen says.