In all cases the ducting needs to conduct the exchaust to the building exterior and needs to terminate in an animal proof vent cover.
Bath fan vents to attic.
But while you can t have two fans with one vent you can make one fan and one vent serve two bathrooms.
A grille in each bathroom attaches to ducts which then fasten to a y connector at the fan.
This setup requires an in line centrifugal fan mounted in the attic drawing air simultaneously from both bathrooms see photo.
When venting a bathroom exhaust fan make sure to vent the air to the outside rather than into your attic where it can cause mold and mildew to form.
The lowdown on venting your bath fan into an attic is that it can be done but it should terminate on the outside.
Options for venting a bathroom exhaust fan include best to worst.
This article describes routing bath exhaust fan duct upwards through an attic or roof space or downwards through a floor or crawl space.
If you vent the bathroom exhaust fan to close to the soffit vents which are vented plates under your homes outer edge and roof your home the air can be sucked right back into the attic from the soffit.
I would by lying if i told you that it will cause problems it may be totally fine.
Bathroom exhaust fans perform an important function by removing excess moisture from your home.
No you cannot vent the bathroom exhaust fan into the soffit vents.
In fact i have seen numerous houses that haven t yet had signs of mold with the bath fan venting incorrectly.
Can you vent a bathroom exhaust fan into the soffit vents.
Bathroom ventilation fan duct routing routing a bath vent duct down out or up through an attic or roof out.
The truth about attic bathroom venting.