Insulating garage roof, correct sequence of execution

So it is more important to provide ventilation than to insulate.

In a room like this for sure - I also find that very difficult. Above all, everyone advises you something different... whether my advice is good or not, I can't tell you either.

In my opinion, proper ventilation is important in the garage. From my experience (I have an existing building), there are ventilation slots in the doors and ideally even an exhaust grille on the opposite wall to allow for a slight "draft." A wet car in the garage brings a lot of water with it, and if you drive into the garage in winter with snow on the roof, you shouldn't be surprised if there are eventually damp spots.
I also have a cellar staircase in the garage, and when there is high humidity (like in recent days), condensate runs down the wall down there because the walls are rather cold down there and probably are not insulated against the floor beneath the garage. The wall is clad with facing bricks, so the water runs down and sometimes there literally is a puddle on the tiles in front of the cellar door. It’s not pleasant, but unfortunately there’s hardly any way to change it without tearing down half the garage. Fortunately, this only happens a few days a year, so you just have to mop it up then. At least I haven’t had any mold problems there so far.

For our brick garage with a concrete flat roof, the following structure was built on the roof (from bottom to top):

[*]Concrete ceiling
[*]Bitumen membranes
[*]Insulation
[*]EPDM membrane (or whatever it is called)
[*]Gravel

For ventilation, the garage has a window that is usually left permanently in a tilted-open position.
Otherwise, you should probably also leave the garage door open from time to time for ventilation.

We are also getting a massive garage with a concrete ceiling, and here too the question arises whether to insulate or not. The garage is unheated and is outside the thermal envelope and has no direct door to the house. Furthermore, I want to maximize the height (car lift), the insulation would give me 10cm of space back. The architect says insulation is absolutely necessary, but I don't see it that way – opinions differ here as well. I believe that insulation actually promotes a wet roof, especially in summer, when warm air meets a cool, insulated ceiling. In winter, the garage should also be rather cool, since salt and heat promote rust. Ventilation will of course be provided through the garage door, window, and ventilation slots. If that is not enough, a duct fan can also be installed. Are there situations where insulation actually prevents condensation with sufficient ventilation?

Hello, if I understood correctly, then the garage is what a garage is supposed to be -> a box in which cars stand. Insulating an unheated room makes no sense anyway. The cold will surely quickly or very quickly penetrate the garage through the garage door and open garage door. What purpose is the insulation supposed to serve then? Insulation does not prevent a room from cooling down; it can only slow it down. So I wonder what you ultimately want to achieve with the insulation? In my opinion, it only costs money and serves no purpose. I would personally maybe install a fan in a garage at most. But even that I would only retrofit if necessary. I think you can build enough hidden gaps in a garage to provide enough ventilation, if you even need that at all. That means to me that, especially a detached garage, should be as cheap and functional as possible. A bit of paint on the outside and done.