As the other person stated, the hotend has two fans. One for part cooling and one to cool the extruder itself. The latter is usually controlled by the printer with no way for you to change it (apart from maybe rebuilding your own firmware) so you will be good to go running at 0%. The issue with this is that some part designs need the plastic to be cooled quickly for things like bridging, which is where you’ll run into issues having the part cooling fan turned off. That probably won’t be an issue when printing a box though.