Is an air conditioner necessary in a south-facing location?

People who appreciate nature and fresh air and the scent of garden, forest, and meadow better find other ways than to hide hermetically sealed buildings in summer and winter.

So we build air conditioners on top of that. Great energy saving.

Additionally, you will find the current floor plans with the marking of which rooms should possibly be equipped with an air conditioner as well as some pictures of the exterior view.

The first offer for equipping the four rooms with a multi-split air conditioner amounts to around €15,000 including materials and installation!

Why is the electricity consumption negligible?

People who appreciate nature and fresh air and the scent of garden, forest, and meadow better manage to do so differently than by hiding in hermetically sealed buildings in summer and winter.

Are there any experience values regarding cooling via controlled residential ventilation and underfloor heating? From what I have read, it seems that the cooling functions there are very limited and that actual cooling down in midsummer can only be achieved with an air conditioner.

That is - especially in new buildings - too expensive. Rough rule of thumb: €1000/kW cooling capacity. A new building should not need more than 5kW. If you operate the thing like your heating (turn on, summer, turn off), often just one indoor unit is enough to go from "I'm dying" to "this is bearable." Especially in combination with FH cooling.
If you want to keep it constantly at 20°, you have to spend a bit more. But not 15k.

I have two reference points: 140sqm old building, continuous cooling at 23-24°, 500kWh, so €150 per year.
135sqm new building, cooling on demand, 300 kWh, so €90 per year.
These are average values from the last two or three summers. And they were not exactly cold.
I consider that negligible.

Deliverer already said it right: one unit preferably high up. Or three in the southern rooms. Cooling on demand or permanently, both are possible and both are effective.

Another problem is humidity and not just the temperatures. If you want a comfortable indoor climate, you have to dehumidify.

15k is definitely way too expensive.

I also have an offer only for the devices without installation from the wholesaler. They offered three indoor units for the attic each with 2.3 KW as well as one unit 5.3 KW for the living room on the ground floor for a total of 10,000 €. But the complete installation is still missing.

I don't know if one unit in the gallery brings much, then the cold air falls through the open space in the gallery down to the basement and does not reach the rooms where it is needed?!?!

I can control the humidity with the already planned controlled residential ventilation, can't I?

For most people, air conditioning is desirable. People who appreciate nature, fresh air, and the scent of gardens, forests, and meadows are better off finding other solutions than retreating into hermetically sealed buildings in summer and winter.

It is real satire. We build energy-saving houses to need less heating in winter. These things become ever more airtight and highly insulated. Great, only a little energy consumption in winter! Now we find that in summer we can no longer get the heat out of the houses. So we install air conditioners. Wonderful energy saving. Of course, when it’s hot, you can power the air conditioner with photovoltaics — that is also a good piece of climate protection.

I find it absolutely legitimate when a builder considers comfortable temperatures in the house and regards an air conditioner as the only option.

Yes, the cost driver is the 5 indoor units. If you reduce that to just three, the costs are halved. (Of course, you can also install only 3 units for 15K... no big deal)

If you find the 15K okay then... go for it... I mean, it's fine. The house will of course be pleasantly cool with the 5 units. So what is the question? Whether it gets cool or whether you can save somewhere?

By the way, what is the wall structure? And what do you imagine under smarthome?

The air is dehumidified and falls downward. The warm air flows in and is also dehumidified and cooled, that is, from all rooms as long as the doors remain open. Until the set temperature is reached. Of course, this is faster and more effective with multiple indoor units.

No, controlled residential ventilation does not work like that. It only dehumidifies the air in winter since an equilibrium between inside and outside takes place here. In summer, when the air inside and outside has almost the same humidity value, nothing is dehumidified by the controlled residential ventilation.

The function of the controlled residential ventilation is almost a one-to-one transfer to the ventilation system in the car. In summer, you cannot cool with it because nothing is dehumidified, and in winter, however, it dehumidifies even if the air stream is set to cold. (Sure, this is only a very rough comparison).