Bedroom too warm - despite the heating being off

Window open, earplugs in, and sleep mask on?

It is simply the case that the temperatures inside the house equalize. The houses are top insulated, so the surrounding rooms help heat the bedroom. Otherwise, you would eventually have the AT in the bedroom. I am probably different here than most. Even in summer, I need something cozy, and at 20 degrees in the bedroom I feel totally comfortable with a normal blanket. It could actually be thicker. I mean the blanket. Not me :)

But you can still easily get a 2 to 3 degree difference in a KFW house. You just have to find a compromise, turn the other rooms down slightly.

So it works for us as well. The bedroom is just under 18°C. Other rooms on the same floor are 21°C and the bathroom is 22°C. The bedroom is completely turned off. The bedroom door is closed during the day, open at night. In a KfW40 timber frame house.

now I became interested, measured this morning,
AT -2.8 degrees
bedroom window open, 16.6 degrees
bathroom 23.4 degrees
living room and hallway 22.8 degrees,
heating costs approx. 3000 kwh electricity per year

But you can also easily get a 2 to 3 degree difference in a KFW house. You just have to find a compromise, turning the other rooms down slightly.

Yes, OK. I wasn't assuming that. Then of course it is possible.

It could still be that the heating loops of the other rooms run through the bedroom? Where is the HKV located? Unfortunately, that is sometimes done wrong as well. That would be extremely bad m

Good hint, thanks. That is actually the case. The "supply line" for the distributor on the upper floor runs straight through the bedroom. But it's under the insulation for the screed and, from a floor plan perspective, it wouldn't have been possible any other way. I have to measure whether it is warmer on the floor there than elsewhere in the bedroom. That would at least be a small explanation:

The discoloration of the sight glasses, do you have a towel radiator in the heating circuit?

No, we don’t. There will surely be an electric towel radiator in the bathroom, but only next winter ;)

I will play around a bit with the temperatures of the other rooms on the upper floor, maybe that will help a little. The bathroom is also directly adjacent to the bedroom, and of course the temperature there is the highest...

Thanks anyway for all the answers so far. Great!!!