In a Miami home the air is humid before anyone takes a shower. Add a hot shower, a small room and a closed door, and the moisture has nowhere to go. A bathroom exhaust fan is what moves it out. When the fan is loud, weak, rattling, or has simply stopped, mirrors stay fogged, paint peels, grout darkens and mildew comes back no matter how often you clean. Replacing the fan is usually a modest job, but getting it right depends on things you cannot see from below: where the duct goes, what circuit the fan is on, and whether the new fan suits the location.
Why exhaust fans matter here
Bathroom exhaust fans keep relative humidity down, which discourages condensation and mold, and the U.S. Department of Energy's Building America Solution Center recommends running them for about an hour after a shower, with a timer for intermittent use (DOE Building America Solution Center). In South Florida, where outdoor air is humid most of the year and the AC is working hard to dry the indoor air, moving shower moisture straight outside takes load off the system and protects the drywall and cabinets.
Signs the fan needs replacing
- It runs but the mirror still fogs and the room stays steamy.
- A tissue held to the grille is not pulled toward it.
- It rattles, grinds or hums louder than it used to.
- It does not start, or starts only some of the time.
- The grille and housing are rusty, or there are stains on the ceiling around it.
- It smells hot or the switch is warm. Turn it off and see burning smells and buzzing.
Venting: outside, not into the attic
Exhaust air has to leave the house. The Florida Building Code, Residential, states that air removed by mechanical exhaust shall not be exhausted into an attic, soffit or ridge vent, and the Building Officials Association of Florida has interpreted that a duct ending beside a vented soffit does not meet it (BOAF interpretation, Florida Building Code). DOE guidance says the same thing: duct the fan to the outside, not into the attic or crawlspace, and reroute or replace a fan that exhausts into the attic (DOE BASC).
Older homes sometimes have fans that blow into the attic, or a duct that fell off its roof or wall cap years ago. In a hot Miami attic, that warm, wet air condenses on the roof deck and insulation. When we replace a fan, we check where the duct actually goes. Ductwork, roof caps and wall penetrations can involve other trades; we will tell you if the route needs one.
Fans over a shower or tub
A fan installed directly over a shower or tub has to be one its maker lists for that location, and many makers require it to be on a GFCI-protected circuit. Broan-NuTone, for example, lists one of its common models as UL listed for use over bathtubs or showers when connected to a GFCI circuit (Broan-NuTone). The fan's installation instructions decide this, and the electrical code (NFPA 70) requires listed equipment to be installed according to its instructions. If your bathroom outlets already trip, our guide to bathroom outlets that stop working explains how bathroom GFCIs are usually wired, and GFCI and AFCI requirements in Florida covers the rest.
Combination units with a light need the same care: the light part must suit a damp or wet location if it sits in the shower zone.
Noise, airflow and humidity sensing
- Sones. Fan noise is rated in sones; lower is quieter. DOE's Solution Center points to ENERGY STAR guidance of 3 sones or less for fans run intermittently and 1 sone or less for fans run continuously (DOE BASC). A quiet fan is one people actually leave running.
- Airflow. Fans are rated in cubic feet per minute (CFM). Size depends on the room and the duct run; a long or kinked duct delivers far less than the label says.
- Efficiency. ENERGY STAR rated ventilation fans must meet efficiency and maximum sound levels, and ENERGY STAR says they use about 48 percent less energy than standard models.
- Humidity sensing. Some fans turn themselves on when humidity rises and off when it falls. In a Miami bathroom that is often the most useful upgrade, because nobody has to remember the switch. A timer switch is the simpler alternative.
- Controls. A separate switch for the fan and the light, a timer, or a humidity control can mean a new wall device, and sometimes an extra conductor.
What the replacement visit involves
For a like-for-like swap, we isolate the circuit, remove the old fan and grille, and check the housing opening, the wiring and the duct connection. We check whether the circuit has the protection the new fan's instructions call for. Then we fit the new housing, connect the duct securely, wire the fan and its control, and test the airflow and the switch.
Some jobs grow. A larger or quieter fan may need a bigger opening or a different duct size. A fan with no duct to the outside needs one. A bathroom that never had a fan, or a remodel that adds lights, heaters and a fan together, is planning work; our bathroom remodeling electrical page covers that. Concrete condo ceilings limit where a fan and duct can go, and building rules apply; see condo electrical repairs.
What to tell us when you call
- Whether there is an existing fan, and whether it has a light or heater.
- Whether the fan is over the shower or tub.
- Whether there is attic access above, and if you know where the duct ends.
- Whether you want a quieter fan, humidity sensing or a timer.
- A photo of the fan grille and the label inside it, if you can see one.
Questions people ask
Can I just replace the motor?
Some fans sell replacement motors or upgrade kits that fit the existing housing. That works when the housing and duct are in good shape and the kit matches the housing.
My fan vents into the attic. Is that a problem?
Yes. The Florida residential code does not allow it, and in a hot, humid attic that moisture condenses. Have it ducted to the outside.
Do I need a bathroom fan if I have a window?
Ventilation requirements for bathrooms depend on the code in effect when the home was built or remodeled. In practice, in Miami humidity, a window rarely clears shower moisture as well as a fan.
Can a ceiling fan go in a bathroom instead?
A paddle ceiling fan moves air around a room; it does not remove moisture. Bathrooms need exhaust. For paddle fans elsewhere, see ceiling fan installation.
Need it looked at?
KRW Electric (EC13012832) troubleshoots and repairs bathroom exhaust fans and ceiling fans in Pinecrest, Coconut Grove, South Miami and Miami Beach, with same-day service when scheduling permits. Call (305) 359-7312 and tell us what you are seeing. We will ask a few questions, tell you whether it sounds urgent, and give you the earliest time we have. Our before you call checklist covers what to have ready, and what happens on a repair visit explains the rest.
Reviewed by Kyle White, KRW Electric Company LLC — licensed electrical contractor EC13012832.
