ᐅ Decommissioning and sealing roller shutter boxes

Hello,

we will most likely install external roller shutters and deactivate our current boxes, which are currently equipped with manual mechanisms.

Do you have any good approaches or ideas on how to best seal and close the deactivated and emptied boxes? I want to avoid creating any thermal bridges or similar issues.

Thanks in advance

Insulation foam?

Good grief!! ;-)