even when not used? that makes 0 sense.
The opposite does apply, as you say, it is fully on when we don't want it on, to that degree.
The first thing is to change the windows to double glazed, then insulate the apartment block.
I had double glazes windows put into flats a few years ago and there were no thermostats, i.e. you could not regulate the temperature.
So in the midst of winter, about minus 15, I would have to open the windows because it was too hot!, the mind boggles.
The almighty administration has since put regulating thermostats on each rad, this is now common practice and should have been done with this gentleman's apartment, built in 2000.
There is a field covered in snow outside the front of my block, where you could clearly see where the hot water was coming from because it was not well insulated and melted the snow in a line.
It is wise to have a back up heating system, solar or a fire place.
Electric heating is obviously quite expensive, so solar can pay off in the long run.
Or a gas combi-boiler, if you have gas.