Experience with reversible operation of the heat pump

Hello,
we are currently in the final stages of planning our single-family house new build (1.5 floors, slab foundation, KfW40 standard, photovoltaic 7 kWp).
Especially this year with its extreme summer, one naturally wonders whether it makes sense to equip the heating system, consisting of underfloor heating with air-to-water heat pump, with reversible operation. Apart from the fact that I do not yet know the additional cost for this function, which will certainly contribute to the decision-making, I am interested in your experiences. It is clear that the "cold" underfloor heating/cooling cannot replace an air conditioning system. However, I assume that, hopefully, an air conditioner is not necessary in a modern single-family house...

- For those who can switch their underfloor heating to cooling mode in summer: Would you choose it again, or was the installation pure waste of money? What did the function cost you (additional price compared to a normal heat pump/underfloor heating) and what would the function be worth to you at most?

- For those who cannot use their heat pump/underfloor heating for cooling: Do you regret the decision—especially now in this hot summer—not to have included this function? In other words: Would you buy such a function from the start today? Especially considering that, according to climate and weather experts, long hot summer periods like this year are expected to become more frequent in the future, even though it certainly will not be the case every year (see 2017, a year without a "real" summer in our area).

Thank you for your opinions, both as answers to the survey and preferably in more detail as text.

I cannot provide experience, as we are currently still in the planning phase ourselves. But one point to consider: the cooling function of an air-to-water heat pump negatively affects the overall balance and may mean that the KfW40 standard is no longer met (if that is important to you), or it must be compensated for. More photovoltaic area, for example.

We were at a model home exhibition yesterday, and some had underfloor heating-cooling. Basically: yes, it was cooler there than in the other houses. But if you sit there for a longer time, you actually get cold feet, even though your head is still sweating. The cold air layer simply didn’t rise but stayed on the floor. I imagine that would be uncomfortable in the long run; normally, you want it the other way around. During the sock test^^ I had ice-cold feet within a very short time, which for me is the surest way to catch a cold.

We have installed and activated cooling via brine. Currently 21 degrees on the ground floor, 23.5 on the upper floor, and 28 in the attic. You need to know that we also have underfloor heating in the attic, which is probably responsible for the cooler temperature on the upper floor. The floor is cold, but it bothers us less than the heat. We are currently wondering whether the air conditioning was necessary, as it has not been in operation yet. We would do it again for the small additional cost.

We installed and activated cooling via brine. Currently 21 degrees on the ground floor, 23.5 upstairs, and 28 in the attic. You should also know that we have underfloor heating in the attic, which probably causes the cooler temperature upstairs. The floor is cold, but bothers less than the heat. We are currently wondering whether the air conditioning was necessary, as it has not been used so far. We would do it again for the small additional cost.

What was additionally necessary to get a cooling function via the brine heat pump? How high was your additional cost?

What else was necessary to get a cooling function via the brine heat pump? How high was your surcharge?

The surcharge was €1250 gross including installation by our heating contractor. At Vaillant, this is a Natural Cooling module that is installed separately on the wall, costing around €900 at the lowest on Google, then without installation.