Air-to-air vs. air-to-water heat pump KFW55 house - cooling function important

Hello everyone,
we are currently deciding between several prefabricated house providers and a major difference is the heating system offered. Some providers install standard air-to-air heat pumps (cooling available at extra cost), others air-to-water heat pumps with underfloor heating and ventilation system (air conditioning can be purchased additionally). Geothermal or groundwater as a heat source are probably not an option for the currently targeted plot. It is a KFW 55 house, initially without photovoltaic for cost reasons, but it should be retrofitted later.

We have already read quite a bit on the subject, but in the end we are laypeople and have difficulty deciding about the heating. It is also important to know that we are very sensitive to heat and therefore want to consider active cooling from the outset. In case of doubt, we would only need to heat/cool individual rooms.

The following advantages and disadvantages are known to us so far:

Heat pump	Advantages	Disadvantages
Air-to-air with cooling function	[*]Heating and cooling in one system [*]Relatively inexpensive to purchase	[*]Noise level, still to be checked (is the noise level different from a ventilation system?) [*]Different temperature control in different rooms more difficult than with underfloor heating
Air-to-water with underfloor heating + air conditioning	[*]Easier to switch to other heat sources [*]Air conditioning works very well with photovoltaic (exactly when there is a lot of sun, you want to cool) [*]Warm feet in winter	[*]More expensive to purchase, especially including air conditioning (exact cost difference is not clear to us yet) [*]Air conditioning without photovoltaic = high energy costs
Air-to-water with underfloor heating with cooling function	[*]Easier to switch to other heat sources	[*]Only a few degrees of cooling possible [*]Cold feet in summer (very important disadvantage for health reasons)

In principle, this results in 43 variants we are currently considering (we were advised against the underfloor heating with cooling function for the reasons mentioned):

[*]Install air-to-air heat pump with cooling function
[*]Install air-to-water with underfloor heating, retrofit air conditioning when photovoltaic is installed and live with the heat until then
[*]Install air-to-water with underfloor heating and air conditioning, live with high cooling costs until photovoltaic is installed

Which variant would you prefer or do you see another one? Do you have an idea which variant would be preferable due to running costs? Since we unfortunately have to watch costs due to a probably rather expensive plot, air-to-air sounds like the better solution to us at the moment.

We would appreciate your assessments.

Assessment: In the end, exactly two sensible solutions remain. Air-water heat pump + air conditioning or exclusively air conditioning.

Why? Air-air heat pump is nonsense in KfW 55. It saves investment at the beginning (cool sales argument), but air-air heat pumps should be installed in houses between KfW 40 and passive house for consumption reasons. Therefore, no further argumentation is needed regarding the (ineffective) cooling option. You wouldn't be happy if a) the cooling is poor and b) you save a five-figure amount at the beginning but have double or even higher heating costs continuously. Not to mention a completely different heating technology with different heat (which for me is a deal-breaker).

If I had to decide: split air conditioning for heating and cooling. Cost-effective, efficient, and bearable in ongoing maintenance.

P.S. Costs are not only measured monetarily. The lack of quality of life is also a cost you have to factor in. Apart from that, it is total nonsense to wait with the installation of an air conditioner. The costs that will arise later for you are significantly higher than for immediate installation. You do not have to turn it on if a few euros per year are too expensive for you (although I do not consider the operation of an air conditioner for a few weeks a year at maybe electricity costs of around €25 per month to be too expensive).

What health reasons speak against a [Fußbodenkühlung]?

From my point of view, Air-to-Air can also be described as follows. You have a heat pump that generates heat, warms the air, and releases it into the room through ventilation outlets. Similar to a car. If the heat generation is not sufficient due to cold outside temperature, you additionally have a "hairdryer" in each outlet that provides the extra heat still needed. You have to decide for yourself whether you like this and whether the savings are worth it. In other words, this clearly explains why it is cheaper. But it is just an exaggerated layman's opinion from the regulars' table. Oh, and Google Proxon.

What health reasons speak against underfloor cooling?

I think the expectations for the cooling are clearly higher than what it will actually deliver. In the office, I often walk barefoot (IT people are allowed to do that!) and on the carpet it feels cool but not cold. Uncooled tiles are worse. If you are sensitive to heat, I would definitely put some thought into shading. Don’t forget about the light when shading; with proper planning, you can shade the sunny sides well and let light in on the other side.

I’ve already written this in some other threads, just briefly: I have cooling through the regular underfloor heating, controlled by the photovoltaic system. It works perfectly and NO, no one has complained about cold feet. The heat just disappears. That it’s sufficient for me is certainly due to a) the very well-insulated house and b) the location at 550m in the foothills of the Alps – in Cologne on the Rhine it probably wouldn’t be enough. A real air conditioning unit simply has significantly more power and also dehumidifies.

Never again a house without cooling. At this location I would gladly use pure underfloor heating cooling again; at hotter/more humid locations I would immediately install a proper air conditioner. Control is nowadays easily possible via Home Assistant, so it can be set to only turn on when the photovoltaic system is producing power – and that without the time delay of the underfloor heating.