Snowbird AC settings for a Cape Coral home

Why an empty house still needs AC

About 18% of homes in Cape Coral's ZIP codes are vacant at any given time, mostly seasonal homes, and 25% across the area we cover. That is a lot of houses sitting closed through the most humid months of the year.

Heat is not really the problem in an empty house. Moisture is. The AC is the only thing pulling water out of the indoor air, and our average dew point in July and August is around 75F. Turn the system off for the summer and the humidity inside climbs toward what it is outside. The EPA says to keep indoor relative humidity below 60 percent, ideally 30 to 50, to limit mold. A closed Cape Coral house with the AC off will not stay there.

LCEC puts it plainly: many unoccupied homes need a small amount of air conditioning every day throughout the summer for humidity control.

The three settings LCEC describes

Setting	What it does	When it fits
Timer, about two hours a day	Runs the AC on a schedule every day	Most mildew protection, per LCEC
Humidistat at 65 percent	Runs the AC only when indoor humidity goes above 65 percent	Least power, per LCEC
Thermostat at 83F	Runs when the house gets warm	Short or infrequent trips only

The reason 83F is not enough for a long absence: a thermostat responds to temperature, not moisture. On a mild, wet day the house can sit below 83F and still be damp, and the AC never runs. Over a long summer that is how you come back to a musty closet and spots on the ceiling.

A lot of newer smart thermostats have a dehumidify setting or can take a humidity sensor. Ask the technician whether your system can control on humidity before you buy extra hardware. If you have a whole-home dehumidifier, the settings above still apply to the AC, but ask how the two should work together.

Before you leave

1. Check the drain line. A clogged condensate line is the most common way an empty house gets water damage from the AC. Pour a cup of white vinegar or water down the cleanout if you have one and confirm it drains outside. If the float switch has tripped before, get the line cleared before you go. See our drain line guide.
2. Put in a new filter. A clogged filter over six months reduces airflow and can freeze the coil.
3. Set the thermostat or timer and write it down. Leave a note on the thermostat so the house checker does not change it.
4. Leave interior doors and closet doors open. so air reaches the whole house.
5. Consider a maintenance visit in spring. rather than leaving with an unknown system. Our maintenance page covers what a visit should include.

Have someone check the house

A setting is only useful if the system actually runs. Capacitors fail, breakers trip after summer storms, and drain lines clog in July whether or not anyone is home. Arrange for a neighbor, a property manager or a house watch service to walk through on a schedule. Ask them to:

• Confirm the air handler runs and the house does not smell musty.
• Look at the floor around the air handler and the ceiling near it for water.
• Check that the thermostat screen is on and still at your setting.
• Check the breaker panel after a storm or power outage.

A cheap humidity and temperature sensor that reports to your phone is a good backup. It will tell you the house is getting damp long before anyone smells it.

If you come back to a musty house

Don't start by booking a duct cleaning. Find out why the moisture got in first: AC off, drain clog, a leak, or a system that short cycles. If there is visible mold on surfaces or in the air handler, the EPA advice on mold applies, and our humidity and mold smell page covers what to check.

Summer here runs long. Recently the first 90F day has come around March 28 and the last around November 10, so "summer settings" covers most of the year. More numbers are on our heat and humidity data page.