Heat pump instead of oil: climate-friendly heating for a 1960s tower block

The eight-storey complex, built in 1966, with 32 residential units in a high-rise development near Düsseldorf has a particularly striking appearance thanks to its original slate cladding - but at first glance it may not seem like the “ideal property” for modernization with heat pumps. After all, when it comes to the topic of heat pumps in refurbishments, people still have ideas about supposed prerequisites such as “façade insulation” and “underfloor heating”. The high-rise apartment building in Hilden meets neither of these requirements: the 32 residential units are equipped with radiators and façade insulation was out of the question due to the slate cladding, which is worth preserving.

Nevertheless, the 60-year-old tower block with 2,300 m² of living space was converted to a regenerative heat pump heating system - with great success. "The system has been in operation since last fall. It runs reliably and everything works," emphasizes heating engineer Per Christensen, who implemented the heating renovation. He had no concerns beforehand, because it all depends on the right planning in advance. “The tenants were informed and involved when the maximum flow temperature was lowered from 75 °C to 55 °C.”  This meant that the radiators, which were oversized during construction, could all remain in the apartments.  There were no doubts about feasibility beforehand. He realized the project together with his partner Dimplex, the market and technology leader for heat pumps with a higher output. Thanks to decades of experience in the field of heat pumps, especially with an output of 20 kW and above, Dimplex planned an individual system solution on site that would ensure a reliable heat supply even under the demanding conditions.

Individual system solution saves energy and costs

Three Dimplex System C LA 60S-TU heat pumps were used, which can be installed flexibly and are specially designed for large projects, such as apartment blocks or office buildings. Dimplex sales representative Christian Hammacher, an expert in heat pump systems in accordance with VDI 4645, supervised the project and explains why this heat pump model was chosen given the local conditions: "The LA 60S-TU can cover a building heat requirement of up to 60 kW and provide flow temperatures of up to 60 °C. The heat pump can also be used for heating, with a COP of up to 60 kW. A COP of up to 4.9 is achieved for heating - and therefore also high seasonal performance factors. The output control increases the efficiency with low heat demand - the operating costs are correspondingly low as a result." Hot water was already being heated decentrally and electrically before the conversion: electronic instantaneous water heaters in each apartment supply hot water directly to the kitchen and bathroom without having to travel long distances.

In order to ensure a smooth changeover, the flow temperature of the existing heat supply in the Hilden tower block had already been reduced over several phases during cold periods. It was possible to maintain the same level of comfort for the residents, so that nothing stood in the way of replacing the old oil heating system with a modern heat pump. As the Dimplex LA 60S-TU naturally meets all legal requirements, the modernization was eligible for a maximum subsidy of 45 percent from BAFA.

Quiet operation convinces residents

The residents' initial concerns about possible noise development were also quickly dispelled. This is because the speed-controlled fans and the sound-optimized compressor room of the LA 60S-TU ensure quiet operation. The correct installation location also plays a role, which was carefully selected in consultation with the local plumbing and heating contractor. The three large air heat pumps are positioned at some distance from the side of the building so that the residents of the 32 apartments are not disturbed by noise. Janitor Uli Schillings draws an all-round positive conclusion: “Since the system has been up and running, you can't hear a thing!”

Throughout the entire project, Dimplex worked closely with the responsible specialist tradesman, Per Christensen Heizungsbau, who coordinated the work on site. Several meetings with the tradesmen on site, support during all stages of construction and expert commissioning and system adjustment by the Dimplex customer service team ensured an optimum result. The intelligent Dimplex master control system, suitable for up to 14 heat pumps in a cascade, allows the system to be controlled as required. And even after commissioning, the system continues to be supported - as part of a service and warranty package of up to twelve years by the regional Dimplex Service on site and remotely at any time. This is because the heat pumps are integrated online via an NWPM touch card, meaning that the system can also be controlled via the Dimplex app and monitored or accessed remotely via the Internet.

Climate-neutral heating - with an existing heat pump

With the new Building Energy Act (GEG), the mandatory switch to renewable energies for heating has been enshrined in law. Consequently, the conversion of existing buildings to renewable heating systems will be a key issue for homeowners in the coming years. The modernization project in Hilden impressively demonstrates that a heat pump can be an efficient, climate-friendly and reliable solution - even for existing buildings with a high heating requirement, without insulation and underfloor heating. After the first heating period, the residents' verdict is consistently positive - or as janitor Uli Schillings sums it up succinctly: “We had no problems at all.”

Video about the project at: https://youtu.be/OSqouJO17jw?feature=shared