Active and Passive Air-Water Heat Pump: Difference in Cooling

I still don't quite understand why you are so hung up on the passive/active distinction. It basically means whether the compressor is running (active) or not (passive). But not whether cooling is possible or not.

Is it only about cooling? As I said, that also works with an air-water heat pump but only actively and not passively. Therefore higher electricity consumption. With photovoltaics, however, this is not so relevant.

With a brine-water heat pump, it works passively, i.e., without a compressor, because the ground is cold enough even in summer, unlike the outside air medium, which can be very warm in summer.

But yes, it sounds like the refrigerator principle. But a refrigerator is also active.

We would like to manage to get the temperature under 27°C in our bedroom on the upper floor in the future; if possible, between 23°C and 25°C would be a dream.

That is a concrete goal. How you can achieve it is not only a question of heat pump technology but also of the house concept, the location of the bedroom, the behavior of the residents, and so on. Give your construction partner as precise specifications as possible in this result-oriented manner, and they should then propose how to achieve it. Something like this: "We do not like heat and wish, for our quality of life (which means this is a prioritized point), a maximum bedroom temperature of 24 degrees. To achieve this, we do not want to have to pay attention to when and where which window or door is open out of convenience. Regarding the location of the bedroom, it is important to us that it does not become a 'basement room cave.' We are willing to invest a bit more in the acquisition of the solution if it results in lower energy consumption."

I still don’t quite understand why you keep harping on the passive/active distinction. It basically means whether the compressor is running (active) or not (passive). But it doesn’t mean whether cooling is possible or not.

I’m trying to express myself more precisely, or rather to use a more appropriate, descriptive example.

There is a refrigerator that can bring the temperature down to 0° and below. Then there is a cooler box that is also electrically powered but can only manage to lower the temperature by maybe 20° compared to the ambient air.

I understand the active air-water heat pump in this example as the refrigerator and the passive air-water heat pump as the electric cooler box.

So my hope is to achieve a noticeably cooler effect with the active air-water heat pump and underfloor cooling than with the passive variant.

Is that correct? If so, can such a system prioritized by me also reduce the temperature on hot summer nights, even when it doesn’t cool sufficiently outside?


I really like your words, but unfortunately, in the real world (at least from what you often read), you more often encounter people (salespeople, consultants, etc.) who promise you everything and exploit the customers’ inexperience, as long as they make a sale. Whether it actually turns out that way afterward is another matter, and the salesperson or consultant doesn’t want to hear anything about it. That’s why I try, as far as possible in advance, to inform myself and, above all, to actually understand. But yes, basically I also agree that this should be left to the professionals or should be left to them...

Again: there is no passive air-water heat pump (as far as I know). It also doesn't make any sense. How am I supposed to passively cool a house with 30 degree warm outside air?

The example with the coolers is also strange. There are the simple ones with Peltier elements and those with compressors, but here too: both active!

And an active air-water heat pump doesn't really cool better than a passive brine-water heat pump. Both can at most circulate water only a few degrees cooler through the floor because otherwise condensation occurs and then mold follows.

So the problem with cooling via the floor is not due to differences like: active, passive, air-water heat pump, brine-water heat pump, etc. but condensation! Here lies the big advantage of a "real" air conditioner, which by design removes moisture.

unfortunately, in the real world (at least from what one keeps reading) you more often come across people (sellers, consultants, etc.) who promise you everything and exploit the customer's inexperience, as long as they make a sale

That is exactly the reason why I always recommend not choosing the price as the first criterion for selecting a construction partner. Always invest in the people and in securing the results – and of course keep an eye on the costs at the same time. Of course, every bit of expertise on the subject helps you – as long as you are aware of the level of abstraction at which you are branching out, that is very helpful. But as soon as you start drawing false or incomplete conclusions from your knowledge, you will move into a self-constructed state of uncertainty. Therefore, it is so important to always keep the actual goal, which you can apparently clearly formulate in contrast to many builders, in mind. Ultimately, it does not matter to you which technology meets your requirements, as long as these are fully formulated.

With an air-to-water heat pump in cooling mode, you get a cold floor. Room air can probably also be cooled a bit this way, but you probably won't get more than a few degrees. If heat in the bedroom really is such a central problem for you, just install an air conditioner. It doesn't cost much for one room and you can cool down to 24°C even when it's 38°C outside if you feel like it.