Underfloor heating defective or too sluggish?

Hi, we feel that our underfloor heating is not working properly.

We have a new building, moved in this year, KFW 55.
With [Luft-Wasser-Wärmepumpe].

When we moved in at the beginning of March this year, the floor was always nicely cozy warm. So, the underfloor heating was noticeable.
Now you hardly notice it anymore.
Of course, the floor is not ice cold but also not as warm as at the beginning.
Temperatures in the rooms around 21 degrees.

Our current problem.
We were on vacation from 12.12. to today, 21.12.
I set the heat pump to holiday mode from 13.12. to 20.12. with a reduction to I believe -4 degrees.
Now we came home this evening and it is ice cold inside.
Down here 18 degrees and upstairs in the children's rooms only 15 degrees.

Is the underfloor heating that slow? I thought it only takes a few hours to heat up?
For us, it has now been over 24 hours since it has been running normally again.
Why is it still so cold?

Strange, 12 hours are more than enough for us.

What is the outside temperature right now? There are outside temperatures at which the heater doesn’t turn on. It’s too warm for it to get going. Especially in autumn, so this weather is enough for itself. For us, it feels cold. I have a little dial on the gas heater, I turn it up three clicks, and then it starts running, don’t ask me if that’s the temperature or the heating curve.

Basically: It is normal with a reasonably sized heat pump that it takes a long time to reheat a house. For me, more than a day. And a noticeably warm floor would be a sign of an inefficiently running heat pump.

I suspect the heating system does not recognize that there is a significantly higher heating demand because it regulates the flow temperature depending on the outdoor temperature and it is currently quite warm. Accordingly, reheating takes a long time. If the heat pump is not already running at its limit, you can temporarily increase the flow temperature manually to make it go faster.

I set the heat pump to vacation mode from 13.12. to 20.12. with a reduction to, I believe, -4 degrees.

Stop the nonsense. You have a heat pump. If you lower the temperature for the vacation, then do it like this:

13.12. - 18.12. if you return on 21.12.

especially when temperatures are like now, around +10 degrees

At the current temperatures, you actually have a problem getting the house warm again. Lowering the temperature in [kfw 55 houses] and air-to-water heat pumps should be avoided. Additionally, the floor in such a house should only warm up at -20°C, otherwise something is wrong..