Sustainable heating: TDT AG incorporates a Hoval heat pump cascade into its refurbishment project

TDT AG relies on renewable energy – with heat from a heat pump cascade and green electricity from its own photovoltaic system, keeping its company building at a pleasant temperature even with radiators installed.

TDT AG is committed to sustainability – something it demonstrates through the large wildflower meadow it has planted and bird boxes it has set up with the aim of establishing biodiversity. Now, it is also committing itself to this aim with its heating system at the company’s Essenbach site. Constructed in 1991, the building has been heated exclusively with renewable energy from air and solar sources since October 2024. Setting this up came with the challenges of the large area of 1610 m² of office space and the 5700 m³ of enclosed space, featuring numerous glass fronts, plus the many different requirements that the office and production areas had. The solution came in the form of two Hoval Belaria pro (24) air/water heat pumps in a cascade, together with the existing UltraGas (50) system from 2011, which is only used as an emergency supply source.

Before the refurbishment work started, the modern, four-storey building had been heated with a gas-fired combined heat and power unit that also provided an emergency power supply. “The combined heat and power unit was getting on in years and would have had to be replaced. Given our commitment to sustainability, we thought the logical next step would be switching to a regenerative heating system”, says Hubert Mirlach. A ground source heat pump was planned at first, but the quantity of groundwater available from the land was not enough. After a brief trip back to the drawing board, two Hoval Belaria pro (24) air/water heat pumps were chosen instead.

Extensive refurbishment work in and around the company building took place even before the new heating system began operation in October 2024. To improve efficiency, the large glass fronts were converted from double to triple glazing and additional insulation was installed behind the radiators, numbering around 100 and distributed throughout the building. These were also replaced

– Franz Ramsauer from installation firm Olzinger GmbH. Finally, a stable foundation was installed in order to provide the outer units of the heat pumps with a secure location despite the presence of a slope.

It was not just the refurbishment work that required a comprehensive approach – the heating solution itself did too. The two heat pumps are configured as a cascade and run alternately week by week. They only work at the same time if they need to, which reduces wear and makes operation more reliable. If unexpected faults occur or if a lot of heat is required, the existing gas boiler – also from Hoval – is ready to spring into action too. So far, however, it has never had to. The electricity for the heat pumps comes from the 34 kW photovoltaic installation, which works in tandem with a storage tank that was installed around a year before the heating refurbishment work took place. “With the PV installation and storage tank, we’ve always had enough energy available – even on rainy days. In the summer months, it works so well that we don’t need to buy any additional electricity at all and can even use the supply for our servers instead of our heating”, says Hubert Mirlach.

The entire system is rounded off by sophisticated building services engineering networked with a KNX bus, which is used to manage temperature, shading and ventilation throughout the building. This ensures the temperature is kept at an ideal level at all times in line with individual needs – fully automatically, with virtually no manual intervention required. Additionally, the improved insulation compensates for the increased inertia in the new low-temperature heating system.

The project work ran just as seamlessly as the equipment. Alongside the quality of the products, Hoval’s service team proved especially impressive:

– Hubert Mirlach, expressing his satisfaction with the project. Franz Ramsauer adds: “Hoval’s support and coordination were simply top-notch throughout the entire project. Everything was so well planned and prepared that all the different trades involved were able to work together seamlessly and the whole thing was completed by a single deadline”. Another factor in the project’s success was the work that took place with an energy consultant, who was responsible for calculating the heating requirements and the radiator configuration.