Combine heat pumps with existing radiators?

Efficient heating of residential buildings with heat pumps: underfloor heating as the optimal solution. While the combination with heat pumps is uncomplicated in new buildings, radiators are often used in existing buildings. Nevertheless, according to Matthias Hartmann, CEO of Techem, the energy efficiency of existing buildings can be improved with heat pumps. The power reserve of the radiators plays a decisive role here. The standard outside temperature, measured over 20 years, influences efficiency. Optimally dimensioned radiators enable the use of heat pumps at a maximum heating medium temperature of 55°C, according to the results of Techem's consumption value study.

The metering service provider's consumption value study includes the analysis of over 130,000 residential buildings in Germany. The heating power reserve was determined in the context of the 70/50/20 design, with a flow temperature of 70°C, return temperature of 50°C and an indoor temperature of 20°C to be achieved. The results show that under these conditions, a power reserve of around 40% is sufficient to enable future heat pump applications with the associated lower system temperatures, based on the operating behavior of radiators.

Power reserve of 40% required:

In 50% of the existing buildings analyzed, the radiators are already generously dimensioned, according to Techem. If there is a power reserve of less than 40%, the radiators need to be replaced, although alternatives with the same width and height are available for common types such as steel radiators and panel radiators, which increase the nominal output by 40-50%. It may also be sufficient to replace radiators in selected rooms. The study concludes that retrofitting would be possible for most of the properties affected. Including the 50% of buildings with sufficiently dimensioned radiators, 90% of the housing stock could therefore be suitable for the use of heat pumps without major interventions.

The consumption value study shows that there is great potential for changing the heat source. Techem examined the situation in around 1.4 million apartments in apartment buildings. According to the latest data, more than half of the analyzed area was still heated with natural gas in 2022, while district heating increased slightly and was in second place at 38%. The use of heating oil fell significantly, from 16% in 2013 to 10% in 2022.

Although heat pumps are not yet widespread in existing buildings, they were already the primary source of heating energy in over half of newly built residential buildings in 2022, according to the Federal Statistical Office. Their share rose from 50.6% in 2021 to 57.0% in 2022.

Source: Immobilien Zeitung