Why Your AC Runs But Your Home Still Feels Humid

I have seen this in Florida homes for years. The air conditioner is running, the thermostat says you are at the set temperature, yet the place feels damp and clammy. That is not how cooling should feel. Below is a straightforward guide to why humidity lingers and what you can do about it, written in plain language so you can make the right call for your home.

Quick Checks You Can Do Today

• Set the thermostat fan to Auto, not On.
• Close and latch doors and windows.
• Check that your air filter is clean and correctly sized.
• Make sure supply and return vents are open and unblocked.
• Look for a slow or clogged drain line at the indoor unit.
• Turn off any smart thermostat “circulate” fan features for now.

How Air Conditioners Remove Moisture

Your system cools the air and it also dries it. Cooling is the sensible load. Moisture removal is the latent load. Warm indoor air passes over a cold evaporator coil. Water in the air condenses on that coil, then drains away. For this to work well, the coil needs the right temperature and the system needs enough run time. When either is off, the house can hit the right temperature but still feel humid.

Why 45 To 55 Percent Humidity Is The Sweet Spot

Most families in our climate feel best between 45 and 55 percent relative humidity. Above 60 percent you start to feel sticky, dust mites thrive, and mold risk goes up. Below 40 percent can feel dry on the skin and sinuses, which is rare here but possible in winter if heating runs a lot.

The Most Common Florida Causes Of A Sticky House

Oversized Equipment That Short Cycles
A system that is too large cools the house fast and shuts off. Short cycles mean very little moisture removal. You get a cold but damp home.

What fixes it:

• Fine tune airflow and controls if the oversize is mild.
• Add a whole home dehumidifier to carry the latent load.
• Replace with a right sized system. Two stage or variable speed equipment runs longer at lower output, which pulls more moisture each cycle.

Airflow That Is Too High Or Too Low

Moisture removal depends on the right airflow across the coil. Too much airflow and the coil is not cold enough to condense water. Too little airflow and the coil can freeze or underperform.

What fixes it:

• Use the correct filter size and MERV.
• Clean the indoor coil and blower wheel.
• Set the blower to the proper speed and verify static pressure.
• Open closed registers and repair crushed or undersized ducts.

Fan Set To On Instead Of Auto

When the compressor stops, a fan that keeps running can re-evaporate water sitting on the coil and send it back into the home.

What fixes it:

• Use Auto for the fan.
• If your system supports it, enable dehumidification that slows the fan during cooling to wring more moisture out.

Low Refrigerant Charge Or Metering Problems

If charge is off or a TXV is not metering correctly, the coil can be too cold or not cold enough. Either way, moisture removal suffers and you may see icing.

What fixes it:

• Have a licensed tech measure superheat and subcooling.
• Find and repair leaks, set the correct charge, or replace a faulty TXV.

Dirty Coils And Clogged Drains

A dirty coil cannot transfer heat and moisture well. A clogged drain line can trip safety switches and stop cooling, which lets humidity bounce back.

What fixes it:

• Clean the coil and pan with the right solutions.
• Vacuum and flush the drain.
• Add an access tee and a float switch for future protection.
• Consider UV lights to keep coil surfaces cleaner between visits.

Outdoor Air Sneaking In

Leaks at doors, windows, recessed lights, attic hatches, and on return ducts pull humid outdoor air into the system.

What fixes it:

• Seal return leaks first, especially in hot attics and garages.
• Add weatherstripping and door sweeps.
• Seal or replace leaky recessed lights with sealed trims.
• Vent bathrooms and kitchens to the outdoors and run the fans long enough.

Thermostat Placement And Settings

A thermostat near a supply vent, a sunny window, or a lamp will misread the room and force short cycles. Some smart settings that run the fan on a schedule can make humidity worse here.

What fixes it:

• Relocate the thermostat to an interior wall away from supply air and sunlight.
• Disable aggressive circulate modes.
• Use supported dehumidify features that coordinate fan and compressor.

Equipment Age And Design

Older single stage systems have a harder time controlling humidity in coastal heat. Newer variable speed equipment slows down to extend run time and keep the coil at a better temperature for moisture removal.

What fixes it:

• If your unit is near the end of its life, plan a right sized, variable speed system with proper duct design and controls.

Florida Fixes That Make A Noticeable Difference

Right Sizing And Longer Run Times

Bigger is not better in our climate. The goal is steady, even cooling with longer cycles. That is how you dry the air and keep comfort steady from room to room.

Coil Cleaning, Drain Maintenance, And Static Pressure

A clean coil, a clear drain, and healthy duct pressure give you the coil temperatures and airflow that moisture removal needs.

Duct Sealing And Return Upgrades

Return leaks are a major source of humidity. We test and seal those first. We also add or resize returns when needed to reduce static pressure and improve airflow at the coil.

Whole Home Dehumidifiers

If you like the thermostat set higher, or humidity climbs during mild weather when the AC barely runs, a whole home dehumidifier tied into the return is a smart solution. It keeps humidity steady without overcooling the house.

Attic Insulation And Ventilation

A cooler, drier attic helps keep the whole system stable. Insulation and proper attic ventilation reduce heat and moisture loads that push through ceiling openings.

How We Diagnose Humidity Problems

Interview And Walkthrough

We listen to when and where the home feels damp, look for sweating vents, check around the air handler, and review thermostat history.

Measure What Matters

We record indoor and outdoor conditions, humidity, temperature split at the supply and return, static pressure, blower speed, and coil condition. If needed, we test ducts for leakage.

Right Size And Right Design

We run a load calculation and review duct sizes, return placement, and total airflow. The goal is the right equipment with the right ductwork so the system can control both temperature and moisture.

Controls That Work For Florida

We confirm the thermostat supports proper dehumidification logic and program it to favor moisture removal without overcooling.

Clear Options And Pricing

You get a plain language plan with quick fixes, cost effective repairs, and replacement options when it makes sense. We explain the expected impact on comfort, energy use, and warranty coverage.

Maintenance Habits That Keep Humidity Down:

• Check filters monthly and change as needed.
• Clean the condensate line each spring.
• Schedule seasonal tune ups to verify charge, airflow, and safety controls.
• Keep supply and return vents clear of furniture and rugs.
• Use bath and kitchen exhaust fans during and after use.
• Consider a small digital hygrometer so you can track indoor humidity.

When Repair Makes Sense And When Replacement Pays Off

If the system is sized well and in good shape, settings, cleaning, duct sealing, and airflow adjustments usually solve the problem. If the system is oversized, aging, or has a pattern of coil and compressor issues, replacement with a variable speed heat pump can deliver better humidity control and lower bills. We size and design the system for your home, discuss financing options, and back the work with strong parts and labor warranties.

FAQ

What humidity level should I target?

Aim for 45 to 55 percent relative humidity for comfort and health.

Will a higher SEER2 unit solve humidity?

Efficiency helps with energy use. Humidity control improves most with right sizing, variable speed, proper airflow, and smart dehumidification controls.

Can a smart thermostat fix humidity by itself?

Only if the equipment supports dehumidify features that coordinate fan and compressor. A basic circulate setting can make humidity worse.

When does a whole home dehumidifier make sense?

When you prefer higher indoor temperatures, during mild weather when the AC rarely runs, or in homes with high indoor moisture loads.

If your AC is running and the house still feels sticky, we can help. Call Florida Air, Inc. for fast after hours emergency service, free in home estimates on new systems, and a 30 day warranty on service repairs. Ask about maintenance plans and our 10 year parts warranty on new installations. Your comfort is our business, and we are your hometown team for hometown service.