Air-to-air heat pump vs air-to-water heat pump vs ring trench collector - differences

We are currently facing the difficult question of which heating concept is right for us. We have to decide on one of the three options:

1.) Proxon (air heat pump)
2.) Air-to-water heat pump with underfloor heating and separate controlled residential ventilation
3.) Ground source heat pump with underfloor heating and separate controlled residential ventilation

Gas is not an option, as no gas lines will be installed in the new development area.

With option 1.), the low initial costs are certainly a major advantage compared to 2.) and 3.). However, we are mostly deterred by the predominantly negative experiences from various internet forums (mainly: heating power is insufficient, high running costs due to high electricity consumption).

Basically, we are more inclined towards 2.) or 3.). But here too, you frequently read about the enormous sluggishness of water-based surface heating systems. Can someone report anything about this? How should I imagine this?

Does this sluggishness, for example, mean that the house cools down significantly in a very short time during a temperature drop outside of 10 degrees, because the underfloor heating cannot keep up?

Or is sluggishness rather meant to describe that heating up a room (e.g., a bathroom from 23 to 25 degrees) takes several hours?

Asked differently: Can the underfloor heating maintain the bathroom constantly at 23 degrees and the other rooms at 21 degrees regardless of the outside temperature?

yes, it works if it is reasonably calculated and dimensioned using room-specific heating load calculation.

Then, for example, with your wishes (bathroom warmer than the rest), it may turn out that due to the small floor heating area in the bathroom, an additional wall area must be planned as wall heating, or the often used purely electric towel radiator would be necessary.

Or the standard heating renovator sets everything to 23°C and turns down the flow in the other rooms, which would not be optimal energetically and hydraulically...

In general, it takes a while for underfloor heating because the screed has to warm up first. And once it is warm, it stays warm for a while. Especially when you have a party with many people, because you don't want the first ones to freeze, so you heat as usual. Then many guests arrive, and their body heat adds extra warmth. A normal radiator is easy to turn on and off. With underfloor heating, that doesn’t make much sense, because by the time the screed cools down, the guests are already gone. This is just one example; with active ventilation you obviously have additional advantages. We (currently without ventilation) regularly do a quick burst of ventilation; fresh air is necessary anyway. Just to say, underfloor heating is slow to react. You can't just turn the heating on and off quickly. Depending on the thickness of the screed, it takes some time. Therefore, the temperature is basically kept constant. That works well for us; we have 21C everywhere, only the bathroom is a bit warmer. Since all new buildings are well insulated, a temperature drop doesn’t matter. Indoor temperature is not lost that quickly. Heating a room within 30 minutes won’t work (without additional heating).

Earlier in the topic, passive cooling was briefly mentioned. We are installing an air-to-water heat pump, which apparently can also cool - at least actively - if I follow some of the advertising slogans. Daikin Altherma 3 R is that. Daikin has good devices.

I did not choose it because of the cooling, but this is just a small side insight. A cooling function of the air-to-water heat pump - is such a thing useful? Does it ultimately just mean cooler floors in summer? (Underfloor heating installed)

I did not choose it because of the cooling, but that's just a small side insight. A cooling function of the air-to-water heat pump – is something like that any good? Does that simply mean cooler floors in summer in the end? (Underfloor heating installed)

Of course, it's not an air conditioner, but you can reduce the temperature by a few degrees.

However, honestly, I'm not a fan when it runs through an air-to-water heat pump, because that consumes quite a bit of electricity. In that case, it might be worth considering installing an air conditioner instead. In the case of a brine-to-water heat pump, where you can cool passively almost for free, I consider it a very sensible concept, both ecologically and economically, but in the case of an air-to-water heat pump... hmm, I'm undecided with a tendency towards not sensible...

and : Thank you for your answers! So, if I decide on underfloor heating, would I have to cover my additional heat demand in the bathrooms, for example, with an electric towel warmer and in the living area with a fireplace? How would that be with the Proxon? Is it similarly slow to respond? What kind of electricity consumption should I expect here? In various forums, you read extremely different consumption figures, sometimes between 3,000 and 4,000 kWh per year and sometimes around 7,000 kWh. Overall, I find the issue of consumption with the Proxon very unclear and in my opinion, it is a high risk—especially since we want to build a "55" only... Has anyone perhaps gathered personal experience with this?