Drilling 53 boreholes, each approximately 250 metres deep, beneath the foundation slab of Skanska’s Nowy Rynek C office building in Poznań presented a significant engineering challenge. The extensive ground-source heat pump installation is a key part of the developer’s strategy to reduce the building’s reliance on conventional energy sources.
Located in central Poznań, Nowy Rynek is a mixed-use development by Skanska Commercial Development Europe, combining office buildings with publicly accessible urban space. At Nowy Rynek C, ground-source heat pumps will work alongside air-to-water heat pumps and rooftop photovoltaic panels to meet the building’s full heating demand in winter and cooling needs in summer, eliminating the need for a connection to the district heating network. This approach goes beyond the supplementary role heat pumps typically play in office buildings of this scale.
The system’s design was informed by detailed geological analyses, Thermal Response Tests (TRT) and energy modelling using EED (Earth Energy Designer). These assessments helped determine the optimal number, depth and spacing of the boreholes, taking into account ground conditions and the building’s projected energy demand. The modelling also assessed long-term changes in ground temperature, helping to minimise the risk of excessive cooling or heating of the ground over the system’s lifetime.
Ground-source heat pumps take advantage of the relatively stable temperatures below the surface, which typically remain around 8–12°C throughout the year. By balancing heat extraction in winter with heat rejection in summer, the system is designed to support efficient, long-term operation.
“In Poland, investors rarely opt for ground-source heat pumps in buildings on the scale of Nowy Rynek C. This is often due to concerns about the complexity of the engineering process, the high cost of drilling and a lack of early-stage planning. We should be looking for new ways to design buildings and plan how they operate, including making bolder use of innovative technologies that enable low-emission heating and cooling,” says Przemysław Kubaś, Project Manager at Skanska Central Europe.
Independence takes centre stage
At the next stage of construction, the ground-source heat pump system at Nowy Rynek C will be complemented by air-source heat pumps located on the roof. Their operation will be supported by an on-site rooftop photovoltaic installation with a capacity of more than 350 kWp.
In addition, being independent of the district heating network gives the owner the option of powering the entire building exclusively with energy from renewable sources, backed by Guarantees of Origin. Energy-saving solutions and the building’s full electrification will result in a building with the lowest possible operational carbon footprint. The projected EP primary energy indicator for Nowy Rynek C is 44.32 kWh/(m²·year), approximately 62% below the maximum value calculated for the reference building under WT2021 regulations, which is 117 kWh/(m²·year) (Source: data from the building’s energy performance certificate dated 22 April 2026).
“From the outset, we designed Nowy Rynek C as a building for the future: one that can adapt to changing market conditions and regulatory requirements. Commercial buildings completed today need to be ready for the environmental and energy challenges of the coming decades. Replacing the district heating network with an innovative combination of ground-source and air-source heat pumps and a photovoltaic installation will allow the building to operate independently of external heat supplies, improve its energy efficiency and reduce operating costs over the long term. This is a deliberate investment decision that not only responds to future environmental and regulatory requirements, but also strengthens the property’s long-term competitiveness and helps maintain its value throughout its lifecycle,” says Konrad Ziejewski, Project Director at Skanska Commercial Development Europe.
