Passive house and a too powerful heat pump? Boštjan faced a challenge during the construction of his house in choosing a heat pump that would efficiently heat the passive house while being appropriately sized for the 140 square meter home. Family Štravs also had limitations in terms of available space for the indoor unit of the heat pump in the boiler room. With this in mind, they faced the challenge of finding a suitable heat pump that would meet their needs and spatial limitations.



Object size: 140 m2

Construction of the object: 2022

Object type: passive house

Heating method: floor heating

Heat pump type: VERSI-O

Heat source: air/water

Management: controllers KT-1 and KT-2A, Cloud.KRONOTERM



When creating his home, Boštjan was determined about three things: he wanted floor heating, a ventilation system, and the smallest possible air/water heat pump – both in terms of size and power. The problem he faced when purchasing a heat pump was that all the ones that met his requirements were too big and powerful. For his house, which is built to passive standards and measures 140 square meters, a heat pump with a power output of 3.5 to 5 kW would suffice. He also knew that the space in the boiler room he had designated for the internal unit was limited. There was no heat pump on the market that met his standards.


At the time Boštjan started building, we at KRONOTERM launched a new, smallest heat pump VERSI, which was an ideal solution for his wishes and needs. This, along with the long tradition of the local company KRONOTERM, were Boštjan’s main reasons for purchasing our heat pump. He jokingly adds: “My wife had no say in the selection of the machinery, but I can confirm that she is extremely satisfied with the choice of the heat pump, as she is always comfortably warm now.”


The VERSI-O heat pump was one of the first VERSI heat pumps installed in Slovenia, installed in December 2021. Although Boštjan did some of the work on the house himself, he left most of it to professionals, including the installation of the heat pump, which he quickly used to heat the concrete floors – screeds. He says the heating temperature reached as high as 50 degrees Celsius at the time.



He was pleasantly surprised by the low noise level from the beginning


Boštjan is extremely satisfied with the modern design of the VERSI heat pump, which can change the color of the external unit’s housing in six shades. He chose the ANTHRACITE color, which best suits their house’s style. The VERSI-O heat pump has a smaller external unit and is incredibly quiet, almost inaudible. He says that visitors often ask him if the heat pump is even working. External units from other providers often disturb people, mainly because of the noise they produce, but the VERSI heat pump is so quiet that he jokes he doesn’t even expect calls from dissatisfied neighbors or passers-by. He is also satisfied because the internal unit takes up only 60×60 cm in his space-restricted boiler room, which is only 2 square meters in size. “You don’t need weather protection, sound insulation, you can choose the color of the housing, and the savings are high – all of these are reasons why the investment in a heat pump quickly pays off,” says Boštjan.



“I’m from the industry, and if it works, it works.” – managing the heat pump


The operation of the heat pump is completely automated, so Boštjan doesn’t intervene much in its operation. At the beginning, he paid more attention to the energy consumption of the heat pump, which he still occasionally monitors through the CLOUD.KRONOTERM application. He finds the application very useful even during longer absences, where he can set a higher temperature in the house when the family is returning home, thus returning to a warm home.


“The intelligence built into the heating system constantly adjusts the operation of the heat pump to achieve the desired indoor temperature.”


He wanted two heating circuits in his house so he could set the temperature by floors, so KRONOTERM’s installers installed the KT-1 and KT-2A room controllers in both floors. Because Boštjan is more technically knowledgeable, he highlighted the awareness that a smart curve is installed in the heating system, but he has not dealt with it since its startup. He occasionally checks the curve’s operation in the Cloud.KRONOTERM application, where he can see how the room temperature constantly adapts despite all external changes.


Heat pump + solar power plant = minimal costs


In combination with the heat pump, they also installed a solar power plant in the house. The main motivation for this investment was to cover all electricity and heating costs and, in the future, also the car. Because they produced 6 MW surplus last year, this year’s investment for the Štravs family is an electric car, which they will use to utilize the surplus energy for driving. He says that this way, they are dependent on the grid, but not completely, and this is an ideal combination for him.


Due to the combination with the photovoltaic system, they have not yet felt the actual heating costs. The VERSI heat pump used 1300 kWh for heating and hot water in just over 6 months, which cost the Štravs family about 130 EUR in 2023, or just over 20 EUR per month. Boštjan says that the costs are in line with his estimates before construction, which he is certainly very satisfied with. As a project designer, he was aware of the savings with the heat pump and knew that heating with it was cheaper than with other heating sources. In addition to savings, he also recognizes other benefits of this type of heating system: ecological advantages and consequently less global warming, efficiency, and high COP.


Collaboration with KRONOTERM


Boštjan was convinced by the following features at KRONOTERM: professional assistance and advice, quick and correct answers, always available service, and availability of spare parts. He also emphasized the flexibility that comes from the fact that both production and development are under the same roof. He is satisfied with his decision to choose KRONOTERM and would gladly recommend it to his acquaintances and friends.



With the first annual check-up, he also joined the extended warranty system, as he believes that it is crucial for the heat pump’s lifespan to be as long as possible.


If you need information about the heat pump, or personal advice, please contact us here.