How to Install or Replace a Bathroom Exhaust Fan

Bathroom exhaust fans are the difference between moist walls and dry ones. A working fan pulls steam and humidity out of the room before it settles into paint, drywall, and insulation—where it breeds mold and rot. If your current fan is noisy, moves no air, or you're installing one for the first time, the job itself is manageable if you're comfortable working in the ceiling cavity and making one electrical connection. The key is planning your ductwork route before you cut any holes, because a fan that exhausts into the attic instead of outside is worse than no fan at all.

1. Kill the Power First. Locate the breaker that controls the existing bathroom light or exhaust fan circuit. Switch it to the off position. Use a non-contact voltage tester on the existing fan housing or wiring to confirm the power is actually off. Do not skip this step.
2. Pop Off the Grille. Climb into the ceiling (on a sturdy ladder or attic platform) and locate the exhaust fan housing. Most grilles are held by friction springs or clips that you push or pull outward to release. Pop the grille down and set it aside. Some fans have a trim ring (the part flush with the ceiling) that unscrews or unclips separately—remove it if present.
3. Free the Ductwork. Locate the flexible duct or metal pipe running from the fan housing toward the exterior wall or roof. If it's flex duct, loosen the hose clamp with a screwdriver and slide the duct off the fan outlet. If it's rigid pipe, you may need to unbolt it or separate it at a coupling. Set the duct aside but do not disturb it—you'll reuse it or measure it for a new run.
4. Disconnect the Wires. Open the junction box on top of the existing fan housing (if it has one) or trace the wiring to where it connects to the home's circuit. You'll typically see a black (hot), white (neutral), and bare copper (ground) wire twisted together with wire nuts or connected in a push-in connector. If you're replacing the fan and keeping the same circuit, take a photo of how they're connected. If the wiring is directly hardwired into a junction box, you may need to unbolt the box from the housing.
5. Lower the Old Unit. The fan housing is typically held to the ceiling joist or fan brace with four bolts or mounting brackets. Unbolt or unclip these fasteners and carefully lower the old housing through the ceiling opening. You may need to angle it to fit through the hole. Once it's free, set it aside for disposal.
6. Size the Opening Right. Look at the hole left by the old fan. If the new fan's housing dimensions are similar or smaller, the existing opening works fine. If the new fan is larger, you'll need to cut the drywall opening wider using a drywall saw or oscillating multi-tool. Measure the new housing mounting flange and mark the opening accordingly, then cut carefully to avoid damaging joists or hidden wiring.
7. Bolt It Down Flat. Hold the new fan housing up into the ceiling opening and position it so the mounting flange sits flat against the drywall and the housing is level. Align the mounting holes with the joist or ceiling supports, then bolt the housing down using the provided fasteners. Ensure it's seated firmly with no gaps between the flange and drywall.
8. Clamp and Route the Duct. Slide the flexible duct (or rigid pipe) back onto the new fan's outlet and secure it with a hose clamp, tightened with a screwdriver until snug but not deformed. If you're using new ductwork, measure the run to the exterior wall or roof, cut to length, and connect using a male/female coupling and clamps every 4 feet. Ensure the duct slopes slightly downward toward the exterior so condensation drains back out.
9. Test the Damper Swing. At the exterior end of the ductwork, check the damper (a flapper door) that prevents cold outside air from entering the house when the fan is off. Open it gently and verify it swings freely, then let it close naturally. If it's stuck or damaged, replace it with a new exterior damper hood. Make sure the damper opening is not blocked by screens, netting, or caulk.
10. Match and Twist Wires. With the power still off at the breaker, match the wires: black to black (hot), white to white (neutral), and bare copper to bare copper or green screw (ground). Twist each pair of like-colored wires together clockwise until you have a solid connection, then screw a wire nut onto each pair, turning clockwise until tight and the nut doesn't spin. Alternatively, use a push-in connector (press bare wire ends into the connector until they click and lock). Tuck the wire connections back into the junction box and verify nothing is pinched or strained.
11. Snap the Trim Ring Home. From below, slide the trim ring (if separate) up into the ceiling opening and position it flush with the drywall. Press or screw it in place per the fan's instructions. Then insert the fan grille from below, engaging the spring clips or fastening bolts until it's snug and level. The grille should sit flush with the ceiling with no gaps.
12. Power Up and Listen. Return to the breaker panel and switch the fan circuit back on. Go back to the bathroom and flip the light switch (or dedicated fan switch) to test the fan. You should hear the motor start and feel a slight pull of air from the room. Turn it on and let it run for a full minute to confirm steady operation. Check that the ductwork isn't visibly sucking in or bulging, which would indicate an airflow problem.