Bathroom fan vent code requirements include no venting to attic areas to help reduce mold or structural problems.
Bathroom exaust into attic.
Your attic is not a temperature controlled environment is never the same temperature as your living space and generally closer to the temperature outside.
Dumping bathroom exhaust into an attic or under roof space invites costly mold contamination frost under the roof in freezing climates moisture damage to roof sheathing possibly even plywood delamination or rot roof failures and shorter roof shingle life.
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.
It may also violate a shingle warranty.
You should never exhaust the bathroom fan directly into the attic.
So can you vent a bathroom exhaust fan into the attic.