How to choose the type of VMC for a bathroom and can we put the evacuation to the attic?
There are point ventilation systems that consist of installing independent electric extractors. The most common are the centrifugal extractors which have a propeller motor. Choose the airflow depending on the size of your bathroom. You can install it on a window, either at the top of the wall if it looks directly on the outside, or connect it to a pipe that would cross the attic and go out on the roof. Remember to create an air inlet in the nearest room for the system to be effective.
Any VMC or exhaust system must open on the roof and not in the attic, even lost... This is the norm and especially logic, because we must not reject the stale air... in the house, even if they are attics!
This may interest you