Is the attic always colder than the ground floor?

Quickly checked. The insulation used is a BAUDER PIR FA 160mm. Then there is something about a PU rigid foam wedge of 80x80 on top.

The insulation can be found quickly. How do I calculate the U-value here? And what should I make of this now? 16cm thickness was used instead of 20, because the roof construction would have otherwise become too large. We were assured that it has better insulation (WLZ).

: higher leakage and lower temperature may be true. But please not 4 degrees difference with the same thermostat setting in all rooms. THAT cannot be, not in a new Kfw70 house, sorry. Nobody can make me believe that. Otherwise, everyone would have the problem. Our neighbors strangely do not...

Well, I also have a KfW70 house and exactly the same values... it is cooler upstairs than downstairs... it is simply more than logical as many have already written here in the thread...

Just a made-up example:

You have a 10 sqm external wall area on the ground floor, which is covered by an intermediate ceiling that does not have any heat losses because it is within the heated envelope.

On the upper floor, you have the same 10 sqm external wall area plus additionally a roof of another 10 sqm through which there are heat losses, as it is directly exposed to the outside world.

Which floor do you think the heating has to work harder to compensate for the heat losses?

You can find the U-value of your roof in the house documents... everything should be stated there...

The higher heat losses in the attic can be compensated by

a) higher flow rate
b) more closely laid heating circuits

If that is not enough, the flow temperature must be increased, but then the heating circuits on the ground floor and upper floor must be throttled in flow.

How high is the flow rate compared to the other floors? If the flow rate is adequate there and possibly already above the other circuits, then there is no air in the system either, your heating engineer is right about that.

Ok, maybe it was a bit unclear so far, so once again:

[*]- The supply temperature was increased from 33 to 43 -> effect on room temperature of 0.2 degrees!
[*]The flow rate on the ground floor and basement was throttled, on the upper floor increased by 0.5L/m -> after 20 hours no result regarding room temperature. It remains exactly the same as before the increase (21.2).
[*]All room thermostats on the attic floor are fully turned up, it can’t go any higher!
[*]Nevertheless, we do not get beyond 21.2 degrees.
[*]Hydraulic balancing was done, but was manually changed again yesterday as described (throttling ground floor + basement, increasing flow on attic floor)
[*]Pipe spacing is 10cm
[*]Flow rate in all rooms on the attic floor at 2L/m
[*]Flow rate in the rooms on the ground floor/basement somewhere around 1L or below.
[*]Room temperatures ground floor and basement at setting 3 on the room thermostat = 22.5 degrees
[*]Room temperatures attic floor at setting 6 = 20.9-21.2 degrees
[*]Thermal imaging camera shows 24.4 degrees floor temperature, 21.1 degrees wall temperature.

Summary: I understand that heat escapes through the attic floor. That it can therefore be cooler than on the ground floor and basement is accepted. But it is not explainable why despite all measures we never get above 21.2 degrees room temperature, DESPITE increasing the flow and the supply temperature. Nothing changes at all! And that is not logical to me! There is no temperature change despite these measures.

How can this be explained? Even if the roof were poorly insulated... if I pump more energy into a room, there must also be more energy remaining somewhere in the room. So a change should be noticeable. But with us, it’s zero point zero...

Have you ever closed all the doors for a few hours, turned off [Kontrollierte-Wohnraumlüftung], and then checked whether the rooms become differently warm? If one room/several rooms differ significantly, you might be able to look for the fault accordingly there.

Turn off the AT control on the heater and just try heating through with a constant flow temperature, e.g. 30 degrees... do the rooms get warmer?