How is the construction boom? Still there?

So a house from the 2000s with ~140sqm I would estimate at around 12000kwh/a at 21 degrees RT and a well-adjusted heating system.

Yes, that fits well. These are my observations/experiences. Although it has nothing to do with the topic... as a comparison for the usual construction methods in other countries: a house from the 2000s with the country's typical ~300sqm at 24 degrees RT in the Krasnodar region (Southern Russia, climate similar to northern Germany) consumes 10000kwh/per winter month.

Whereas with the Russians, behavior certainly also plays a role. An acquaintance of mine constantly left the windows tilted open in winter and always washed the dishes under running water. That is customary in [Novosibirsk]...

While with the Russians, behavior certainly plays a role as well. An acquaintance of mine permanently tilted her windows in winter and always washes dishes under running water. This is common in Novosibirsk...

Does she do that in Novosibirsk or here? I assume that here in Germany the costs involved limit such behavior; unless, cliché, cliché, ;-) she is incredibly wealthy. But then she probably wouldn’t wash dishes and ventilate herself. ;-) And, regarding the building boom, does she plan to build or does she already live in her own home?

Does she do that in Novosibirsk or here? I assume that the costs involved here in Germany act as a limiting factor; unless, cliché, cliché, ;-) she is incredibly rich. But then she probably wouldn’t wash the dishes and air out herself. ;-) And, topic building boom, does she plan to build or does she already live in her own home?

She lives in an apartment block and only knows that the electricity (current) comes from the socket and the water is hot from the basement. :D

Lives in a rented apartment and that's why she is here. Behavior is not so easy to change either, maybe something will change about that this winter ;)

except, cliché, cliché, ;-) she is incredibly rich. But then she probably wouldn't do the dishes and ventilate herself. ;-)

No, if you have always done it that way, habits are hard to break. It is a long-term process. But the bill helps immensely. If it has to be paid by oneself.

That is common in Novosibirsk...

Yes, from childhood on. You simply don't know it any other way. Exactly like the huge houses (if you managed to get out of the panel building or were never inside) and at least 24-25 degrees everywhere. Because below that everything is just too cold.