Insulate the garage concrete ceiling or not?

I also think it makes little sense if an unheated garage is only insulated on the ceiling. We will probably skip the insulation, just lay a bitumen membrane on the roof after concreting and that's it. I will think about the air circulation.

That's right!!!

Our garage is being insulated. Additionally to the interior wall. Important is, as already written by others, good ventilation. is integrated into our ventilation concept. There is also Lan (for charging station) and Wifi Accesspoint. Either the full program or nothing at all. Otherwise you will create more problems for yourself. In most areas it does not get cold enough for you to have subzero temperatures in the uninsulated garage. Better to install a duct fan.