Bathroom Exhaust Fans: Why They Matter in Georgia Humidity, and Replacing One

A bathroom in Georgia is already fighting the humidity outside. Add a hot shower and no working fan and the result is mildew on the ceiling, caulk that goes black every few months, paint that peels above the shower, and a mirror that stays fogged. The exhaust fan is what fixes all of that, and most of the fans in local houses are either builder-grade units that move almost no air, or fans that stopped working years ago and nobody noticed because they were never loud enough to hear.

How to tell yours is not working

• Hold a square of toilet paper up to the grille with the fan running. If it does not hold, the fan is not moving meaningful air.
• The mirror is still fogged ten minutes after a shower.
• Mildew on the ceiling or in the grout, especially in the corner above the shower.
• The fan is loud but nothing changes in the room. A worn motor spins and rattles without pulling air.
• Dust caked on the grille. It has been years since it was cleaned, and the airflow is choked.

Sizing

Fan capacity is rated in cubic feet per minute. The basic rule is one CFM per square foot of bathroom for a standard ceiling, with a minimum around 50. A large primary bath, a separate shower room, or a bathroom with a soaking tub wants more. A fan that is slightly oversized on a timer or a humidity sensor is better than one that is exactly sized and never runs long enough.

Where it must vent

Outside. Not into the attic. A fan that dumps warm, wet air into the attic soaks the insulation and the underside of the roof deck, and in our climate that becomes mould and rot in a couple of seasons. We find this in a surprising number of houses, usually because the original installer ran the duct up and left it. If your attic has a bathroom duct that ends in the open, that is a fix that matters more than the fan itself. Our attic insulation post explains what that moisture does up there.

Choosing a fan

• Noise rating. Measured in sones. Under 1.0 is quiet enough that people actually leave it running. Builder fans are often 3 or 4 sones, which is why they get switched off.
• Humidity sensing. The fan turns itself on when the room gets humid and off when it clears. The single best feature for a household that forgets the fan.
• Timer switch. A wall switch that runs the fan for 20 or 30 minutes after a shower and shuts off. Cheap and effective, and it works with any fan.
• Integrated light or heater. Useful, but a heater draws a lot of power and may need its own circuit.
• Duct size. Many good fans want a 4-inch or 6-inch duct. If the existing duct is 3-inch, plan to replace it or choose a fan that adapts.

What replacement involves

With attic access, the old housing comes out from above, the duct is checked or replaced, the new housing is mounted to the joist, and the wiring is connected in the fan's own box. From below only, the ceiling opening sometimes needs to be enlarged slightly for the new housing and a trim ring covers it. Adding a timer or humidity switch is a swap at the wall. Most replacements are a couple of hours, more if the duct has to be rerouted or a roof cap installed.

A new fan pairs well with a bathroom re-caulk, since the mildew that ruined the old caulk was the fan's fault. Our caulk post covers that side, and both fit into one handyman visit.

Questions we get

Can I just clean the old fan?

Cleaning the grille and the fan blade helps a fan that is choked with dust. It does not fix a fan that was never adequate or a motor that is worn out.

Does a window count as ventilation?

Code in many places allows an operable window instead of a fan. In practice, in a Georgia summer, nobody opens the window and the room stays wet. Install the fan.

Can the fan go on the same switch as the light?

It can, and it is how most builder bathrooms are wired. A separate timer switch is better because it lets the fan run after you have turned the light off and left.

Get the bathroom drying properly

Wright Way Services replaces bath fans and fixes the ducts they connect to across Newnan, Peachtree City, Sharpsburg, Senoia, Tyrone and Fayetteville. Call (770) 301-4638 or request service.