More in Bathroom
Turn off your power at the breaker. Then, remove the existing light fixture.
From the attic, find a safe location, away from the joists and any wiring or pipes. Jab a screwdriver down through the ceiling to the center of your location. Do that in two spots about a 1' apart along the joist to have a reference point.
In the bathroom, use a level to draw a line connecting the two holes to mark the joist location (Image 1).
Mark the area to be cut out using the vent as a template (Image 2).
Score the lines with a utility knife to prevent the plaster from cracking, then cut out the opening with a reciprocating saw.
Up in the attic, set the fan housing in place and screw it to the joists.
Connect the supply wires to both the fan housing and the light. First the ground wires, then the white common wires and finally the black and red supply wires.
Plug the light into its outlet and connect the rest of the globe.
A double switch will run the fan and the light. Be sure to connect the red wire to the switch you want to control the fan. Attach the flexible duct to the vent and the housing adapter.
Attach the fixture. After a little ceiling repair, the installation is complete.