It is because of this that many builders tend to advise against this method.
Install bathroom vent into attic.
Drill a reference hole draw a mark on the bathroom ceiling where you d like to install the vent fan.
Remove your old exhaust fan.
Remove the grill cover.
Dangers of wet bath exhaust vent air re entering the attic.
Now where the discharge point is is going to be up to you.
This involves running ductwork from the fan usually though an attic and out through the roof.
Use a circuit tester to ensure that the power is turned off.
Bathroom exhaust fans perform an important function by removing excess moisture from your home.
Both bathrooms are vented by a single in line fan that has one exhaust vent running through the roof.
Bathroom exhaust fans are not required by most codes.
In lieu a window 3 feet square or more capable of being opened at least halfway will suffice.
You should never exhaust the bathroom fan directly into the attic.
Each fan vents separately out the roof.
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.
That will take it from the bath exhaust fan to a discharge point.
A lot of options.
For optimum performance locate it between.
In order to accomplish this the roof has to have a hole cut in it.
The attic bathroom will need electricity to supply at least two 20 amp gfci outlets and one switch controlled ceiling light.
Either way the vent will have to go directly to the outside and installed with a vent hood cover.
Do not spill bath vent air into the building attic or roof cavity where it will condense on and damage building insulation roof sheathing possibly framing and where it will certainly encourage mold growth.
Turn off the breaker box.
So what you want to do is you want to install a duct a vent duct and you can use flex duct for this.
Use an extra long 3 8 inch diameter spade bit to bore a reference hole through the ceiling and into the attic.
You might have to remove a few screws to get it out.
Install bathroom electrical circuits.
These are easy to use and can be purchased at most home improvement stores.
Measure the vent fan.
No you cannot vent your bathroom exhaust fan into the attic.
Depending on the location of the bathroom it may be easy to vent the exhaust fan through the roof.
One in line centrifugal fan can be mounted in the attic to exhaust the moisture from two bathrooms.
See details at bathroom vent codes.