Florida Humidity and Mold: Keeping Indoor Humidity Under Control
You can't do anything about the air outside a Sarasota home. From June through September, the dew point regularly sits in the 70s, and the rainy season brings a storm most afternoons. What you can control is how much of that moisture stays inside. Mold needs moisture to grow, so indoor humidity is the most important prevention lever you have.
The Numbers That Matter
- Indoor relative humidity: the EPA recommends keeping it below 60%, ideally between 30% and 50%. In Florida, 45 to 55% is a realistic year-round target for many homes.
- Dew point:the temperature at which air condenses. When it's high outdoors, any cold surface (a duct, a vent, a window) becomes a place for water to form.
- 24 to 48 hours: roughly how long wet porous material can take to start growing mold, per the EPA. Fast drying matters.
A digital hygrometer costs little and is the simplest way to know where your home stands. Put one in a bedroom and one in the room that feels most humid, and watch them for a couple of weeks.
Your AC Is Your Dehumidifier
In most Florida homes, the air conditioner does nearly all the moisture removal. A few things affect how well it does it:
- Run time. A system pulls the most moisture during long cycles. Oversized units cool the house fast and shut off, leaving the air cool but damp.
- Fan setting.Leaving the fan on "on" instead of "auto" can blow moisture off the wet coil back into the house between cycles. "Auto" is usually better for humidity.
- Maintenance. A clean coil, a clear drain, and a fresh filter all help. See AC mold in Florida homes.
- Humidity controls. Some thermostats can run the system longer to dry the air. Ask your HVAC company if yours can.
Room by Room
| Room | Main moisture source | Habit that helps |
|---|---|---|
| Bathroom | Showers | Run the exhaust fan during and 20 to 30 minutes after; make sure it vents outdoors, not into the attic |
| Kitchen | Cooking, dishwasher | Use a range hood that vents outside; check under the sink regularly |
| Laundry | Dryer, washer hoses | Confirm the dryer vents outdoors; replace rubber washer hoses with braided ones |
| Closets | Stagnant air on exterior walls | Leave doors cracked; don't pack items against exterior walls |
| Lanai and sliders | Humid air when doors are open | Keep sliders closed while the AC runs |
| Garage | Air handler overflow, wet storage | Check the floor around the unit; store items off the slab |
Leaving the House Empty
This is the single biggest mistake in Sarasota County's seasonal communities. Turning the AC off for the summer, or setting it very high, lets indoor humidity climb to outdoor levels. Within weeks, closets, mattresses, upholstery, and cabinet interiors can grow mold.
- Keep the AC on at a moderate setting, or use a humidity control setting if your thermostat has one.
- Consider a dehumidifier that drains to a plumbing drain, set around 50%.
- Have the condensate line flushed and the float switch checked before you leave.
- Shut off the main water valve if the house will sit for weeks.
- Open interior doors, closets, and cabinet doors.
- Arrange for someone to check the house, including the hygrometer reading, every couple of weeks.
Venice and Englewood have a lot of seasonal homes. See the Venice and Englewood pages for local patterns.
When Humidity Isn't the Whole Story
If your hygrometer stays in range and you still find growth, or the musty smell won't leave, there's probably a leak somewhere: the roof, a window, plumbing, or the AC drain. That calls for an inspection with moisture readings, not a better dehumidifier.
