A Central Texas home needs a whole-home dehumidifier when indoor humidity stays above the 50 to 60 percent range even with the air conditioner working properly. Leander, Cedar Park and the rest of Travis and Williamson counties sit in the Department of Energy's hot-humid climate region, and in that climate a correctly sized AC does not always remove enough moisture on its own, especially in spring and fall.
Is Central Texas actually a humid climate?
Central Texas is classified as humid by the federal government, not just by how August feels. The Department of Energy's Building America climate guide places both Travis County and Williamson County in the Hot-Humid region, IECC climate zone 2A.
That guide defines a hot-humid region as one with more than 20 inches of annual precipitation and long stretches of muggy weather, measured as a 67°F or higher wet bulb temperature for 3,000 or more hours during the warmest six months. Homes here are built and equipped under the same humidity rules that apply along the Gulf Coast.
What humidity should a house be at?
The EPA recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent relative humidity. ENERGY STAR gives the same 30% and 50% range as the optimum for a building and notes that anything above it may promote mold growth.
Carrier's guidance is a little tighter: consider a dehumidifier when indoor humidity consistently exceeds 50%. The Department of Energy's Building America Solution Center sets the line for warm-humid climates at keeping indoor relative humidity below 60%. Any reading that sits above those numbers for days at a time is worth acting on.
Why doesn't my air conditioner keep the humidity down?
An air conditioner removes humidity only while it runs long enough for moisture to condense on the indoor coil. The Building America Solution Center explains that a home's cooling load has two parts, a temperature part and a humidity part, and that a conventional system dehumidifies well at peak load because it runs for long stretches.
On mild days the AC reaches the thermostat setting quickly and shuts off, so it removes proportionally less moisture and indoor humidity rises. The Solution Center says the effect is worse on cloudy or humid days and in newer, energy-efficient homes, which need less cooling but carry the same moisture load. Carrier makes the same point: on milder, humid days the AC may not run long enough to dry the air, and dehumidification is needed most in spring, summer and early fall.
An oversized AC makes the problem worse. In a home with an air conditioner that is too big, the Solution Center notes, the thermostat is satisfied before moisture can condense on the coil, so the temperature drops while the relative humidity climbs. Correct sizing starts with an ACCA Manual J load calculation and Manual S equipment selection.
Signs your home is holding too much moisture
The clearest sign is a hygrometer reading that stays above 50 to 60 percent. Carrier recommends checking with a hygrometer or a compatible thermostat, and lists the visible signs as condensation on windows or walls, musty odors, and mold or mildew.
- A cold, clammy feel. A Home Innovation Research Labs TechNote published through the National Association of Home Builders describes the "cold and clammy" complaint as a typical result of high indoor humidity.
- Turning the thermostat down to feel comfortable. The same TechNote notes that occupants of humid homes tend to compensate with a lower summer thermostat setting.
- A musty smell that comes and goes. ENERGY STAR describes a space with an intermittent musty odor as slightly to moderately damp.
- Condensation on the inside of windows. Carrier identifies it as a sign that indoor humidity is too high.
What to rule out before buying a dehumidifier
A dehumidifier controls humidity; it does not fix a leak or a system that is wrong for the house. Carrier says a dehumidifier is not a substitute for correcting active leaks, flooding or visible mold, and the NAHB TechNote says supplemental dehumidification is not meant to compensate for oversized HVAC equipment or a leaky building.
ENERGY STAR recommends reducing moisture at the source first: bath and kitchen vent fans, a clothes dryer vented outdoors, and repaired outdoor faucets. It also notes that home sealing and duct sealing improve a whole-home dehumidifier's performance and lower its energy use. If water is getting into the house, or the AC drain is backing up, we covered that in AC unit leaking water.
What are the options besides a dehumidifier?
There are three ways to add humidity control, and the right one depends on the equipment you already have. The Building America Solution Center lists dehumidification controls that run the AC longer at a slower fan speed, a stand-alone dehumidifier, and a dehumidifier integrated with the central system.
| Option | How it works | The catch |
|---|---|---|
| Enhanced dehumidification on the AC | Slows the indoor fan and may over-cool by 2-3 degrees so the coil pulls more moisture | Needs a compatible thermostat and variable speed air handler, and does nothing in the shoulder seasons when the AC is not cooling (NAHB TechNote) |
| Portable dehumidifier | Dries a single room | Limited reach, and the bucket or hose has to be managed (ENERGY STAR) |
| Whole-home dehumidifier | Uses the home's ducts to dry the whole house, often installed permanently | Needs a drain routed by an HVAC professional (ENERGY STAR) |
Who a whole-home dehumidifier makes sense for
ENERGY STAR says a whole-home dehumidifier carries significant benefits for relatively well sealed homes with central air that see humidity readings above 55% consistently throughout the house. If you live in a humid climate and have central air conditioning, ENERGY STAR adds, an ENERGY STAR certified whole-home unit may be the right choice.
The NAHB TechNote explains why the shoulder seasons matter: in energy-efficient homes, air conditioning is less effective at removing humidity at part load and in the months when cooling is not normally needed. A whole-home unit keeps working then, which an AC setting cannot do. That matters most in a newer, tightly built home, the kind ENERGY STAR describes as relatively well sealed.
What we install
As a Carrier factory authorized dealer, Comfort Pros installs the Carrier Performance Whole-Home Dehumidifier. Carrier lists it in two sizes, removing up to 80 or up to 100 pints of moisture per day, ENERGY STAR certified, with a MERV 8 washable filter, and able to tie into the existing HVAC system or run on its own.
We start by measuring. Our indoor air quality assessment checks humidity, the drain and the equipment sizing before recommending anything, and if a simpler fix like a fan setting, a duct repair or an airflow correction will do the job, we say so first.
Comfort Pros serves Leander, Cedar Park, Georgetown and Liberty Hill, licensed under TACL# TACLB116912E. If your house reads high on a hygrometer this fall, call us and we will tell you whether it needs a dehumidifier or something cheaper.