By Chad Wiswall, Owner & Lead HVAC Technician, Alabama HVAC License #92244
If you walk into your house in July, set the thermostat to 72, and still feel sticky, your air conditioner is doing only half its job. In Central Alabama, controlling temperature is the easy part. Controlling moisture is what separates a comfortable home from a clammy one, and most of the calls I get in July and August are not really cooling problems. They are humidity problems wearing a cooling problem mask. This guide is part of our complete guide to HVAC in Central Alabama.
The Alabama humidity reality
Montgomery, Prattville, Wetumpka, Pike Road, Auburn, and the rest of the River Region sit in what the Department of Energy calls a "mixed-humid" climate zone. Outdoor dew points in July and August routinely hit 73 to 78 degrees Fahrenheit, and on the worst afternoons we push past 80. For context, indoor comfort generally starts breaking down once relative humidity climbs above 55 percent, and most HVAC engineers target 45 to 50 percent indoor RH as the sweet spot. The Environmental Protection Agency recommends keeping indoor humidity between 30 and 50 percent to limit mold growth and dust mites.
That gap (an 80-degree dew point outside, a 50 percent RH target inside) is what your HVAC system fights every summer day in Alabama. And a standard, oversized, single-stage AC unit is the wrong tool for the job.
Why a standard AC removes less moisture than you think
An air conditioner cools your house by passing warm indoor air across a cold evaporator coil. When that air hits the cold surface, water vapor condenses out (the same way water beads on a cold glass of tea) and drains away. That dehumidification only happens while the coil is cold and the blower is running.
The problem is that an oversized AC cools the air to setpoint very quickly, then shuts off. Short, hard run cycles mean the coil never gets cold enough for long enough to wring real moisture out of the air. You hit 72 on the thermostat, the compressor shuts off, and the relative humidity in the house is still sitting at 60 to 65 percent. That is exactly what feels "sticky" or "muggy" even though the thermostat says 72.
This is the single most common humidity complaint I get in Alabama: "the temperature feels right, but the house feels gross." Nine times out of ten, the system is oversized, short-cycling, and removing nowhere near enough latent load.
Sensible heat vs latent heat (and why this matters)
HVAC engineers split cooling load into two pieces:
- Sensible load is the heat you can feel and a thermometer can read. Dropping a 78-degree room to 72 is removing sensible heat.
- Latent load is the heat tied up in water vapor. Pulling moisture out of the air takes energy too, but the thermometer does not see it.
In Phoenix, sensible load dominates and latent load is a footnote. In Alabama, latent load can be 30 to 50 percent of your total cooling load on a humid August afternoon. An AC system sized purely on square footage ignores this and ends up oversized for sensible load (so it short-cycles) while completely undersized for latent load (so the house stays clammy).
This is why the Manual J load calculation the ACCA (Air Conditioning Contractors of America) requires is supposed to break out sensible and latent loads separately. When someone tells me they "just sized it by square footage and a rule of thumb," I know we are about to talk about humidity.
Three signs your humidity is out of control
You do not need a hygrometer to spot the symptoms (though every Alabama homeowner should own one, they are 12 dollars on Amazon and I will reference one in the FAQ below).
Sign 1: You crank the thermostat down lower and lower and still feel sticky. You used to be comfortable at 74. Now you are at 70 and still uncomfortable. That is a humidity complaint, not a temperature complaint. Lowering setpoint forces longer runtimes, which removes more moisture, which is why it sometimes "works." But you are paying a 30 percent power bill premium to compensate for a humidity problem.
Sign 2: Condensation on windows, doors, or in closets. When indoor RH climbs above 60 percent and outdoor surfaces (like a window pane on a cool morning, or a tile floor in a north-facing room) drop below the indoor dew point, water condenses. You will see fogging, beading, or in worst cases, dark spots in corners and closets.
Sign 3: Musty smell or visible mold in closets, bathrooms, and HVAC closets. Mold needs 60+ percent RH to grow comfortably. If you can smell that "wet basement" smell anywhere in the house, your indoor humidity is too high somewhere.
What actually controls humidity in an Alabama home
There are five tools in the toolbox. Most homes need two or three of them working together.
Right-sized, variable-speed HVAC system
The biggest single fix for most homes is replacing an oversized single-stage system with a properly sized variable-speed (or at minimum two-stage) system. A variable-speed compressor can run at 30 to 50 percent capacity for long stretches on humid-but-mild days, keeping the coil cold and the blower moving air across it for the dehumidification benefit. You get longer runtimes at lower power draw, which is the holy grail of humidity control. Daikin and Mitsubishi inverter systems are the gold standard here. Trane and Bryant offer strong variable-speed lineups too. Goodman has solid two-stage options at lower price points.
Whole-house dehumidifier
For homes where a new HVAC system is not in the budget, or where the cooling load is genuinely small (well-insulated newer construction, smaller footprint) but the latent load is still high, a dedicated whole-house dehumidifier installed in the return ductwork is the answer. Units from Aprilaire and Santa Fe are the most common installs we do. A 90 to 130 pint-per-day model handles most homes in our service area. It runs independently of the AC, on its own humidity setpoint, and removes moisture without overcooling the house.
Proper duct sealing and insulation
Leaky return ducts pull humid air directly from your crawlspace or attic into the system. In Alabama, crawlspace humidity in July can hit 90 percent RH. A 10 percent return-side duct leak in that environment is dumping gallons of water into your indoor air every day. Sealing returns with mastic (not foil tape) is one of the highest-ROI moves you can make.
Crawlspace encapsulation (where applicable)
For homes with vented crawlspaces in Central Alabama (which is most pre-2000 construction), encapsulating the crawlspace with a sealed vapor barrier, sealing the foundation vents, and adding a small dehumidifier to the encapsulated space dramatically cuts the moisture load on the entire house. This is not strictly an HVAC contractor's scope, but the crossover with our work is significant, and I will refer you to qualified encapsulation contractors when it makes sense.
Bath fan and kitchen hood usage
Smallest item, free to fix. Every shower puts 0.5 to 1 pound of water into your house. Every pot of boiling pasta puts another half pound. If your bath fan and range hood are not vented to the outside (or if you do not turn them on), you are adding moisture every day. Run the bath fan during and for 20 minutes after every shower. Run the range hood when you cook.
What the right indoor humidity feels like
The target is 45 to 50 percent RH indoors year-round, with a hard ceiling of 55 percent.
At 50 percent RH, a 75-degree house feels comfortable. At 65 percent RH, the same 75-degree house feels oppressive and most people start cranking the thermostat down. The energy savings from getting humidity right are real: every 10 percentage points of RH you remove is roughly equivalent to 2 to 3 degrees of "felt" temperature, meaning you can run the thermostat 2 to 3 degrees warmer and feel the same comfort. That is real money on your power bill in July.
What we actually recommend for most River Region homes
If you are calling us with a humidity complaint, the diagnostic walk usually lands on one of these three recommendations:
- System replacement with variable-speed equipment. Best long-term answer for homes with 15+ year old single-stage systems. We size with a full Manual J, install with proper Manual S equipment selection, and commission with a humidity verification visit two weeks later.
- Add a whole-house dehumidifier to existing equipment. Best answer for homes with 5 to 12 year old systems still in good condition. A properly installed Aprilaire or Santa Fe unit gives you independent humidity control without replacing the AC.
- Seal ducts, encapsulate crawlspace, fix the obvious leaks first. Best answer when the system is fine but the building envelope is leaking moisture in. Sometimes the cheapest fix is the right fix.
We will tell you straight which one fits your home. We do not have a quota for whole-house dehumidifier sales. If your problem is a 14-year-old oversized single-stage condenser that needs replacement, that is what we say. If it is a leaky crawlspace, that is what we say.
FAQ
What is a healthy indoor humidity level for an Alabama home in summer?
45 to 50 percent relative humidity is the comfort sweet spot. The EPA recommends staying below 60 percent year-round to limit mold growth and dust mite populations. Above 55 percent indoor RH, most homeowners notice the house feels "sticky" even when the temperature is at setpoint.
Will a portable dehumidifier from Lowe's solve my humidity problem?
Maybe for one room. A 50-pint portable from a big-box store can dry out a basement or a single bedroom, but the 4 to 6 pints per hour it removes is not enough to keep up with a 2,000 square foot Alabama house in July. You need a whole-house unit (90 to 130 pints per day) installed in the ductwork to make a measurable difference across the entire home.
Can I just turn the thermostat way down to dry the house out?
It works, but it costs you. Lowering the setpoint forces longer compressor runtimes, which removes more moisture. The tradeoff is a 20 to 35 percent higher power bill compared to running a properly sized variable-speed system at a normal setpoint. It is a workaround, not a solution.
How do I measure my indoor humidity?
Buy a hygrometer. AcuRite, ThermoPro, and Govee all make reliable models for under 15 dollars on Amazon. Place it in a central living area, not directly above an air vent, and read it after the house has been closed up for at least an hour. If it consistently reads above 55 percent in summer, you have a humidity problem worth addressing.
Does a heat pump dehumidify as well as a standard AC?
Yes, in cooling mode a heat pump is identical to a standard AC for dehumidification (same evaporator coil, same condensate drainage). Some variable-speed heat pumps actually dehumidify better than single-stage standard ACs because of the longer, lower-capacity runtimes. The brand and capacity stage matters more than the heat pump vs straight AC distinction.
Need help with humidity control in Montgomery, Prattville, Wetumpka, Pike Road, Auburn, Dadeville, or anywhere else in our 16-city service area? Chad's AC Direct has been keeping Central Alabama homes comfortable since 1993. Alabama HVAC Contractor License #92244, BBB Accredited A+, 1,247 reviews at 4.9 stars. Call Montgomery at 334-264-6464 or Dadeville at 334-478-1438 for a free home humidity assessment. Buy Direct, Pay Less.