Bathroom exhaust fan replacement

Why bath fans matter

Showers put a lot of moisture into a small room. A working fan pulls it out before it settles on walls, ceilings and mirrors. When the fan is weak or noisy, people stop running it, and peeling paint, mildew spots and swollen door frames follow.

Signs a fan needs replacing

• The mirror stays fogged long after a shower.
• The fan rattles, hums or grinds.
• Holding a tissue to the grille, it barely moves.
• Paint peels on the ceiling near the shower.
• The fan does not run at all.

Replacement options

Many fan makers offer replacement motor and grille kits that fit their older housings, which avoids cutting the ceiling. Other upgrades use a new housing sized to fit the existing opening. Quieter fans have lower sone ratings, and higher airflow ratings move more air.

Fans with a humidity sensor or timer switch keep running until the air is dry. Fan-light combinations replace a separate light.

Duct and exhaust

A fan is only as good as its duct. Crushed, disconnected or long flexible ducts cut airflow. Fans should exhaust to the outside, not into the attic.

We check the duct connection at the fan and as far as we can reach. If the duct needs rerouting through the attic to a new roof or wall cap, we tell you first; roof penetrations are not work we take on.

Scope

See the full list of electrical work we take on.

Sizing a bath fan

Fan airflow is rated in cubic feet per minute. A common rule of thumb for small bathrooms is roughly one CFM per square foot of floor area, with more for larger rooms, high ceilings or a separate shower and tub. Long or bent duct runs reduce real airflow, so a fan rated a bit above the minimum helps.

Sones measure noise; lower is quieter. A quiet fan gets used, which matters more than a strong one that stays off.

Controls that keep fans running

Most moisture problems come from turning the fan off too soon. A countdown timer switch lets you set the fan to run after you leave. A humidity-sensing fan or switch turns on when moisture rises and off when it drops.

A fan-light combination wired to separate switches lets the fan run without the light. All of these install in the existing switch box when there is room and the right wires.

Mildew and paint after fan replacement

Once the fan works, clean mildew spots with a bathroom cleaner and let the area dry. Peeling ceiling paint can be scraped, primed with a mildew-resistant primer and repainted. If the drywall is soft or stained through, a patch may be needed. We can handle the patch and paint after the fan is replaced.

What to send

A photo of the grille, a photo with the grille removed showing the housing and any label, and a photo of the switch. If you can see the duct in the attic, a photo helps too.

More questions

Can a bath fan be too strong? Very large fans in small, tight bathrooms can pull air from other parts of the house. Sizing to the room avoids that.

Should the fan run during the shower? Yes, and for a while after.

Older fans in valley homes

Many bathrooms in midcentury tract homes have small fans in the ceiling that were never strong, ducted with thin flexible pipe that has sagged or pulled loose in the attic over the decades. Some vent through a wall cap that is clogged with lint or bird nests. A new fan in a housing like that underperforms, so we look at the whole path.

Clearing a wall cap, reconnecting a loose duct at the fan collar and sealing it with foil tape are part of a good replacement. Rigid or semi-rigid duct with fewer bends moves more air than a long sagging flex run. If the attic is too tight to reach the duct safely, we note it and work from the bathroom side.

What a visit looks like

We turn off the breaker, take down the grille, and unplug or disconnect the motor. If a motor kit fits the housing, we install it and test. If the housing must change, we cut the old one free, fit the new housing to the joists in the same opening, connect the duct with a new collar and foil tape, and wire it to the existing cable.

Then we install the grille, run the fan and check airflow with a tissue test. We clean up insulation and dust that falls during the work.

More questions

Can you add a light to my fan? A fan-light combination unit can replace a fan-only unit when the opening and wiring allow.

Grille cleaning between visits

Pop the grille down every few months and wash it in warm soapy water. Lint and hair packed into the louvers choke airflow long before the motor wears out, and a clean grille often quiets a rattle on its own.

Photo checklist