Noticeable cooling effect in air-to-water heat pump

We were promised a cooling of 6-8 degrees.

Yes, maybe on day 1… but the sun shines for several days in a row more often… then it's over and the heat comes.

Now I will probably have to get a mobile air conditioner for the really hot days.

Don't do that. Buy a proper fixed unit. Install it at the highest point and enjoy the pleasant temperatures.

The mobiles are bad already just because they are so loud that you can't run them at night ….

Yes, maybe on day 1… but the sun shines for several days in a row more often… then it’s over and the warmth comes.

Don’t do that. Buy yourself a proper solid system. Install it at the highest point and enjoy the pleasant temperatures.

What does the highest point mean?

Upper floor / ceiling, preferably airspace/stairwell

Yes, maybe on day 1… but the sun often shines for several days in a row… then it's over and the heat comes.

Don't do that. Buy yourself a proper fixed system. Install it at the highest point and enjoy the comfortable temperatures.

Regarding point 1: We were told something different here as well. We already used thicker insulation between the attic and the upper floor, although it was said here too that it’s not necessarily needed. Probably nonsense again.

Regarding point 2: In the upper floor, due to the sloping roof directly at the window, we don’t really have space for a fixed system. You have to position it close to the window, right? Do I then need multiple outdoor units for several rooms?

The insulation obviously helps, but in both directions, meaning it keeps the heat outside. But, and this is a big but, the insulation is also there to keep the heat that is already inside the house in. So eventually you end up with a sauna without countermeasures.

No, you do not have to install the system near the windows. It is more important that the air can move freely. Ideally in all directions. That is why open floor plans are ideal.

Exactly how the system is set up must ultimately be clarified in detail. It is also a question of cost. Of course, it is possible to have one indoor/outdoor unit per room, but also multisplit systems where you have one outdoor unit that serves several indoor units.