No you cannot vent the bathroom exhaust fan into the soffit vents.
Bath fan vents to attic.
Venting through a roof vent or exhausting them in the attic could cause moisture problems and rot.
I would by lying if i told you that it will cause problems it may be totally fine.
In all cases the ducting needs to conduct the exchaust to the building exterior and needs to terminate in an animal proof vent cover.
The lowdown on venting your bath fan into an attic is that it can be done but it should terminate on the outside.
The truth about attic bathroom venting.
Bathroom ventilation fan duct routing routing a bath vent duct down out or up through an attic or roof out.
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.
This setup requires an in line centrifugal fan mounted in the attic drawing air simultaneously from both bathrooms see photo.
Bathroom exhaust fans perform an important function by removing excess moisture from your home.
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.
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.
A grille in each bathroom attaches to ducts which then fasten to a y connector at the fan.
Vent your bath and kitchen exhaust fans through the roof through a special roof hood.
But while you can t have two fans with one vent you can make one fan and one vent serve two bathrooms.