Cooling with heat pump via underfloor heating?

We find summer especially unbearable at high temperatures combined with high humidity. Whether brine-water heat pump or air-water heat pump, the humidity that ultimately causes the muggy and uncomfortable feeling is not reduced by them. Only an air conditioner can do that. Cooling via heat pump is nice, but not comparable to an air conditioning unit. ...

Unfortunately, the argument about the muggy air is very often omitted here, thanks for this hint. We also decided against cooling with the summer bypass of the air-water heat pump and are now additionally getting an air conditioner. I agree: on the one hand, the extreme temperatures are getting higher and, on the other, even at "only" 28 degrees there can be very unpleasant humidity. The summer bypass of the air-water heat pump doesn't help me at all in that regard.

We chose air conditioning and against the special cooling function of the air-water heat pump. I’ve heard from most sources that on really hot days, when you want to cool, lowering by 2-3°C achievable via air-water heat pump/floor pipes is not enough. It was important to us to have effective cooling especially on days above 35°C, and if it’s 37°C outside, I simply don’t want to have 34°C inside the house.

That was exactly our reason not to do it.

Eventually, the heat gets into every house—planning or not. And then you end up with the losing ticket, as not only is the cold outside, but the heat is held inside as well. Then only an air conditioner helps.

That’s how it is, and in the long run, I can’t imagine it being comfortable to always walk/sit on a cooled floor while it’s still muggy warm upstairs....

Thank you! You describe your experience starting from 28°. Do you also have experience with cooler starting temperatures (i.e. how far can you go down from e.g. 24°)?

Unfortunately, I cannot share any experience with lower temperatures since I do not see any cooling demand below 25 degrees. The limiting factor is the dew point. With my cooling system, you can cool the room down to about 4 degrees above the dew point; below that, the pipes (which must be significantly cooler than the target temperature) start to sweat. Specifically: the cooler it is outside, the stronger you can also cool inside.

[*]My conclusion based on a concrete example:
Summer day without active cooling: temperature in the attic at 28 degrees. When I activate the cooling, I get down to 24 degrees (less is difficult due to condensation on the pipes). For me, as a heat-sensitive person, this is exactly the difference to sleep comfortably in the attic. The PERCEIVED reduction in heat stress is significant!
The function is therefore excellent for preventing the interior rooms from heating up despite high outside temperatures.

Thanks for the report!

We are still waiting for the offer for the cooling function from our heating installer.
3-4 degrees already make a big difference in our current apartment as well. When the bedroom has warmed up during the day despite all measures and you open the windows wide in the evening, I notice that a 3-degree cooling can already be the difference between "barely bearable" and "suitable for sleeping."

In the end, it’s always a question of price. Air conditioning is clearly better.
But:
How many hot days a year do you have in which you personally can no longer tolerate it?
And is the approximately 4000 euro price difference worth it to you personally?

The limiting factor is the dew point.

That is exactly why the effect is even less the more humid the air is, therefore: An air conditioner is not only about cooling but also about dehumidifying. This should not be overlooked.

Exactly for that reason, the effect is all the less the more humid the air is, therefore: an air conditioner is not just about cooling but also about dehumidifying. That should not be overlooked.

Absolutely correct.

As I said, it is important to me to distinguish between opinions and real EXPERIENCES, since I have read the argument "humidity stays the same anyway" several times in this thread.
Concrete experience in my house:
- without cooling function: approx. 28 degrees at 60 percent relative humidity
- with air-to-water heat pump cooling function: approx. 24 degrees at 72 percent relative humidity
The latter feels (despite higher relative humidity) SIGNIFICANTLY more pleasant.

Experience in my parents' house:
With air conditioning it goes down to 24 degrees or less at 30 percent humidity. Clearly fresher, but in the long run (for some people) also more unpleasant due to very dry air, keyword "I get sick from air conditioning."

If both cost the same, I would choose the air conditioner. Cooling 200 sqm with air conditioning costs, however, in my case, five times as much as the heat pump cooling function.

So, my experiences with both (air conditioning + air-to-water heat pump cooling) are on the table. What is better individually is now up to everyone to decide.

In my opinion, the crucial answer is still missing here:

THERMAL CONVECTION

As is well known, cold air wants to go down and warm air rises.
No one would come up with the idea to install radiators on the ceiling.

Using cooling surfaces at the bottom therefore brings little benefit, because you want to cool down the warm room air above.
Instead, you only get cold feet and keep a hot head.
For this, you would have to operate at least a solid fan.

Therefore, the answer to the original question is:
yes, but it works more poorly than well.

The poor cooling efficiency could still be tolerated if this
cooling is only used a few days per year.

But this solution does not make you happy.