... We are planning a new building and are now facing the question of whether we should choose built-in or mounted roller blinds. ....
Some say that the mounted ones contribute more to the insulation of the house than the built-in ones. Others say that this is nonsense and that mounted roller blinds are rather used for renovations.
Has anyone of you had experience and can give us advice?
Be careful!
You are mixing up the terms there. Make sure you don’t end up buying exactly the opposite of what you actually want.
A
mounted roller shutter box sits above the window frame, is usually as thick as the wall thickness, and can be plastered on the outside.
Depending on where the opening lid is (in case of repair or replacement work), the inside of the box can also be treated (wallpapered, plastered, etc.) depending on the manufacturer.
This roller shutter box is insulated and easy to install (often already pre-assembled at the factory when ordered together with the windows).
However, this is one of the more expensive options to buy roller shutters.
In contrast, the
attached roller shutter box (or surface-mounted roller shutter) is located on the outside of the window frame and is usually visible.
Example photo:

Here, the service lid (maintenance lid) is on the outside.
In the drawing, the box is round. Square boxes are cheaper.
The advantage of this variant is that it is cheaper and can also be retrofitted relatively easily.
However, it is very rare in new buildings.
An intermediate solution (with a good price/performance ratio) is a
mounted roller shutter box with plaster carrier plate.
Here, the lid can be plastered on the outside and thus disappears into the wall.
It either works with lintel offset (window is mounted further inside) or if the full thermal insulation is thick enough, the windows can also be mounted "normally" and then finished flush with the full thermal insulation.
It should be noted that the box becomes larger the higher the window units are (logically, the more roller shutter slats need to fit inside).
Especially for new buildings, I consider this variant interesting because the price plays a significant role.