KRONOTERM's heat pump VERSI-I is unique as it doesn't have an external unit. We've been developing it for three years, and it has also gained recognition in the Netherlands. Currently, the heat pump is operational with 35 satisfied individuals (article/data from 2022). Heiko Haasjes is one of them. "This is the future," he exclaims.


Jacco Langebeeke, a business partner of KRONOTERM from the Netherlands, vividly remembers the moment when he sat at the kitchen table with a concerned neighbor. Just a few weeks earlier, the neighbor had installed an outdoor unit of an air/water heat pump on his canopy. Unfortunately, the noise created by the pump disturbed him when trying to fall asleep.

“Neighbors enjoy low electricity bills, and I’m dealing with this annoying noisy device,” he disappointingly complained. This moment inspired Jacco Langebeeke with an idea: “What if we didn’t need an outdoor unit anymore?”


Langebeeke believes that more and more people are interested in transitioning from gas to a more economical form of heating. However, he sees two challenges with heat pumps. Geothermal heat pumps require rearranging the entire yard, while air/water heat pumps need an outdoor unit, which is not always practical. He stated, “I started by improving the sustainability of homes with geothermal heat pumps, but the installation required the arrival of drilling trucks, turning the yard into a muddy disaster. Moreover, after installation, the outdoor unit looked like some kind of machinery, which was not attractive to anyone. Then I switched to air/water heat pumps, but investors still needed an outdoor unit. Because the Netherlands is densely populated, it is not always possible to place it everywhere.”


Jacco Langebeeke thought excitedly: the solution would be an air/water heat pump without an outdoor unit. Despite having a good idea, he didn’t receive a response from Dutch developers. “Until four years ago, when I came across KRONOTERM at the ISH fair in Frankfurt. I shared my idea and was invited for a discussion. In Slovenia, 50 percent of houses have a heat pump, while others still heat with oil-fired stoves. Installing an outdoor unit on historic buildings is not allowed, and you also have to ask all neighbors for permission. That’s why KRONOTERM was open to alternative solutions.”


At KRONOTERM, we have developed the VERSI-I heat pump without an outdoor unit, which is versatile as it provides heating, cooling, and hot sanitary water. Additionally, it is equipped with the latest technology, ensuring high operational efficiency and excellent performance. Currently, 35 individuals, mainly professionals, are using VERSI-I in the Netherlands. Langebeeke says, “Everyone is thrilled and trusts the concept of the VERSI-I heat pump. I only hear enthusiastic feedback.”


One of the owners of VERSI-I in the Netherlands is Heiko Haasjes from Doorn. He had a desire to make his house more sustainable. “We were already thinking about it when we moved,” says Haasjes. “We actively searched for a house that wasn’t too old and found a twin built in 2003. At that time, we formulated a ten-year plan because thinking long term is crucial for sustainable living. First, we improved the house’s insulation, installed underfloor heating, and ensured ventilation. Although we had a heat pump on the list, it wasn’t a top priority. Everything changed when the war broke out in Ukraine, and it became clear that gas prices would rise dramatically.”


“With the heat pump, I was surprised by how quiet it is. It operates quietly and hums steadily, similar to a refrigerator. When you close the bedroom door, you don’t hear it.”


They already had a specific optimal insulation level for their home and a need for heat. “At that time, we were already successfully managing gas consumption, but I still wanted to take a step further and completely give it up. When I learned about Jacco Langebeeke from the company Zorgeloos Gasloos, I connected with him. He offered me something new – the VERSI-I heat pump. I was particularly attracted by the fact that it doesn’t require an outdoor unit on the roof, which often causes noise and is not aesthetically pleasing. Even though VERSI-I was a new product on the market, I received positive recommendations from several installers. They also emphasized the use of high-quality components in the heat pump, which gave me a lot of confidence in the product.”



The heat pump has been operating at Haasjes’ home since early November 2022. “What really surprised us is how quietly the heat pump operates. The sound is unobtrusive, similar to the hum of a refrigerator. When we close the bedroom door, we don’t hear anything anymore. Moreover, it always provides us with pleasant warmth. It works just as we expected,” says Haasjes. The heat pump was installed in the location where the central heating boiler was previously placed, and heat recovery was added. Instead of an outdoor unit, two large pipes are connected to the heat pump. One pipe draws in air through the facade, while the other pipe expels air through the roof.


The use of the heat pump can be fully controlled through the application. “Most issues can be resolved remotely, which means that maintenance is practically unnecessary. This has many advantages because you don’t have to enter into expensive maintenance contracts, and a technician only needs to come if a malfunction really occurs.”


Haasjes is so enthusiastic about VERSI-I that he freely promotes it as its ambassador.


“This is an excellent solution for those who want to switch to heating without gas. In fact, I think this is the future.”


Like Haasjes, Jacco Langebeeke is also confident in the success of VERSI-I. He is currently collaborating with major contractors and looking for installers who would like to sell VERSI-I in the Netherlands. “I truly see VERSI-I as my child. I believe that without innovation, it will be challenging to take steps toward a sustainable world.”




If you also wish to transition to a green way of heating, we are available at or at the phone number 080 23 22.

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