In Southwest Florida, your air conditioner does two jobs. It cools the house, and it pulls moisture out of the air. When a home sits empty for the summer, the second job matters most. Heat on its own rarely ruins anything, but months of damp indoor air can lead to musty smells, mildew on fabrics and cabinets, warped wood and mold. This guide covers how to set up, service and monitor your A/C so it keeps the house dry while you're away. For the bigger picture on mold, see our guide to mold and humidity in a closed-up Florida home.
Why the A/C is your main humidity control
As warm air passes over the cold coil inside your air handler, moisture condenses into water. That water drips into a drain pan and runs out through the condensate line. Every hour the system runs, it removes water from the house. If the A/C is turned off, or set so warm that it barely runs, that drying stops, and humid outdoor air slowly works its way in through doors, windows, the attic and the ductwork.
The opposite problem can happen too. A system that is too large for the house, or that runs in short bursts, may cool the air quickly without running long enough to remove much moisture. If your home feels cool but clammy, mention it to your A/C technician.
Settings to discuss with your A/C company
- Don't turn the A/C off when you leave for the season. This is the most common and most expensive mistake seasonal owners make.
- Pick a set temperature with your technician. The right setting depends on your equipment, insulation, shade and whether you have a dehumidifier. The goal is a setting warm enough to save energy but cool enough that the system runs regularly and keeps humidity down.
- Use a humidity setting if you have one. Many modern thermostats show indoor humidity, and some can run the A/C or a dehumidifier based on it. The U.S. EPA recommends keeping indoor humidity below 60% to limit mold growth. Ask your technician how your thermostat handles this.
- Leave the fan on "Auto," not "On," unless your technician tells you otherwise. With the fan running all the time, moisture on the coil can blow back into the house instead of draining away.
- Write the settings down and give them to whoever checks the house, so a well-meaning visitor doesn't change them.
Service the system before you leave
Schedule a maintenance visit with an A/C company a few weeks before you head north, so there's time to fix anything they find. A typical visit includes:
- Clearing the condensate drain line. In Florida, a clogged drain line is one of the most common causes of water damage in empty homes. Algae and sludge build up in the line, the pan overflows, and water soaks the ceiling, closet or floor around the air handler.
- Checking the float (safety) switch. Many systems have a switch that shuts the A/C off if the drain pan fills. That prevents a flood, but it also stops cooling and drying. Your technician should confirm it works, and your home watch provider should know what it means if the A/C is off.
- Cleaning or checking the coils, the drain pan and the outdoor unit, and confirming refrigerant and electrical parts are in good shape.
- Inspecting ductwork in the attic where it's accessible. Leaky or poorly insulated ducts can sweat and drip in a hot attic.
Ask whether a maintenance plan with regular visits makes sense for your home. Many SWFL A/C companies offer them, and the visits can be scheduled while you're away if someone can let the technician in.
Filters
- Install a fresh filter right before you leave, using the size and type your system calls for.
- Don't over-tighten airflow. A very restrictive filter can reduce airflow in some systems. Ask your technician which filter rating fits your equipment.
- Plan filter changes while you're away. If you're gone for many months, ask your home watch provider or A/C company to change the filter on a schedule. Leave spare filters in an easy-to-find spot.
Condensate line care between visits
Some technicians suggest adding a drain-line treatment or pouring a cleaning solution into the line's access port on a schedule. Others prefer to clear the line during service visits only. Ask what your technician recommends for your system, and don't pour anything into the line unless they've told you what's safe to use. Make sure your home watch provider knows where the drain line exits the house, so they can check that it's dripping when the A/C is running.
Is a dehumidifier worth it?
For some homes, the A/C alone keeps humidity in a good range. Others, especially homes with high ceilings, lots of glass, older equipment or a history of musty smells, benefit from added dehumidification. Options include:
- A whole-home dehumidifier installed with your duct system by an A/C company. It can remove moisture without overcooling the house.
- Portable dehumidifiers for a single room or closet. If you use one in an empty house, it needs a drain hose to a floor drain or sink. A bucket fills up and the unit stops.
Ask your A/C company for a written quote and an explanation of why it would help your specific house.
Alerts and monitoring
- A Wi-Fi thermostat or sensor can alert you to high temperature, high humidity or a loss of power. Share the alerts with your home watch provider, so someone local can respond.
- A water sensor near the air handler and under the drain pan can warn you about an overflow before it does much damage. Our guide to preventing water leaks in an empty home covers sensors and shut-off valves in more detail.
- Keep the internet and power on if you rely on smart devices. A power outage after a storm can leave the A/C off for days, so ask for a visit afterward to confirm it restarted.
What your home watch provider should check
A good home watch company will look at the A/C on every visit. Ask that their checklist includes:
- The thermostat reading matches your settings, including humidity if it's shown.
- The system is running and the air coming out of the vents is cool.
- No water in or around the air handler, the drain pan or the closet floor.
- The condensate line is dripping outside when the system runs.
- No musty smell when they first walk in, and no new stains on ceilings near the air handler or vents.
- The outdoor unit is clear of debris, vines and storm damage.
Ask for a written report with photos after each visit. Our guide on how to choose a home watch company lists more questions to ask.
Other ways to keep the house dry
- Leave interior doors, closet doors and cabinet doors open so air can move.
- Make sure towels, linens and clothes are completely dry before you close up.
- Keep bathroom and kitchen exhaust fans in working order and close windows tightly.
- Keep gutters and downspouts clear so water drains away from the house; see gutter companies.
- Have the roof checked after major storms by a roofer, since a small roof leak can feed humidity and mold.
If something goes wrong
If your home watch provider finds the A/C off, water around the air handler or a musty smell, have an A/C company out quickly to fix the cause and get the system running. Ask them to take photos. If there's water damage, call your insurance agent before anything is removed. If you see or smell mold over a larger area, a licensed mold assessor can test and recommend next steps. In Florida, mold assessment and remediation are licensed activities; you can check a license at myfloridalicense.com.
When you come back
Walk the house, check the air handler closet, swap the filter, and note anything that seemed off. Our opening your home guide and closing checklist cover the rest of the seasonal routine. Keep your A/C company, service dates, filter size and thermostat settings in the free My Florida Home app.
General information only. It is not legal, insurance or engineering advice. Check with your insurer, HOA and licensed professionals.
More guides: Snowbird Home Checklist for Southwest Florida · Hurricane Prep Checklist for SWFL Homeowners · How to Choose a Pool Cage & Lanai Screen Company · How to Choose a Pool Service in Southwest Florida · How to Choose a Hurricane Shutter Company in Southwest Florida · Mold and Humidity in a Closed-Up Florida Home: What Snowbirds Should Know · After a Hurricane: A Return Checklist for Seasonal Owners in Southwest Florida · How to Hire and Check a Contractor in Florida: A Guide for Seasonal Owners · Preventing Water Leaks in an Empty Florida Home · The Snowbird's Closing Checklist for a Southwest Florida Home · Hurricane Prep for Absentee Owners · How to Choose a Home Watch Company in Southwest Florida · Shipping Your Car South: A Snowbird's Guide · Opening Your Southwest Florida Home for the Season