The most expensive mistake in Florida seasonal home ownership costs nothing to make. You turn the air conditioning off on your way to the airport, because why pay to cool an empty house.
Here is what happens next.
Why an empty house needs the AC running
With the system off, an unoccupied Florida house climbs past 90 degrees through the summer. Humidity climbs right behind it, and unlike temperature, humidity does not go back down when the sun sets.
Those are close to ideal conditions for mold. It can establish in weeks, not months. Remediation on a house that has spent a summer above 70 percent relative humidity runs into figures that dwarf a season of running the air conditioner at 80 degrees.
Heat is not really the problem. Humidity is. And the air conditioner is your only humidity control.
The settings
Temperature: 78 to 82 degrees. Treat 82 as the ceiling rather than the target. You are not keeping the house comfortable, you are keeping the system cycling often enough to pull moisture out of the air.
Humidity: under 60 percent. That is the number that actually matters.
Humidistat: set to 58 percent. This one needs explaining, because the mismatch looks like an error. Humidistat sensors commonly drift, and can read as much as 10 percentage points away from actual. Setting 58 when your target is “under 60” is the margin that protects you when the sensor is optimistic.
If your system runs on temperature alone with no humidity control, that is worth fixing before you leave. A humidistat lets the system run on moisture rather than temperature, which is exactly what an empty house needs.
Before you leave
Fit a fresh filter. A filter that starts the summer half-loaded finishes it fully blocked, and restricted airflow through a whole cooling season is how evaporator coils freeze.
Clear and treat the condensate drain line. This is the big one. In Florida humidity the drain line grows biological gunk, and a blocked line either shuts the system down on the float switch or backs up into the air handler and through your ceiling. Of the three things that fail in an empty house, this is the one that does structural damage.
Clear the outdoor unit. Cut back vegetation, move anything stacked against it, and give it room to breathe. Storm season will add debris on its own without you starting from a deficit.
Replace the thermostat batteries. A dead thermostat is a system that is not running, and you will not know.
Install a smart thermostat. This is the single best investment for a seasonal home. It lets you see indoor temperature and humidity from wherever you are and alerts you when conditions drift. That turns a catastrophic discovery in November into a phone call in July.
What actually fails while you are away
In our experience it is nearly always one of three things, in this order:
- The condensate drain line backs up. Either the float switch shuts the system down and the house sits at 95 degrees for months, or it overflows and you come back to water damage.
- The filter clogs. Airflow drops, the coil ices, and efficiency falls off a cliff.
- Storm debris or overgrowth blocks the condenser. The system runs hot, works harder, and can trip out entirely.
All three are cheap to prevent and unpleasant to discover from a doorway with your luggage still in the car.
Coming back
Book a startup visit before you arrive rather than after. Filter, drain line, condenser, refrigerant charge, and a general check, done a few days ahead, means the house is cool and dry when you open the door.
It also means that if something did go wrong in July, you find out about it with time to fix it, instead of on the first hot afternoon of your stay.
If you would rather not think about it
That is what a seasonal home programme is for. A departure visit that sets the system up properly, an optional mid-season check, and a startup visit before you return.
It is a small amount of money against the cost of a house that spent five months at 85 percent humidity.