Why Indoor Humidity Is So High in Myrtle Beach (and What to Do)

Myrtle Beach sits in one of the most humid regions in the country. Summer dew points routinely hover in the mid-70s — air so moisture-laden that stepping outside feels like walking into a greenhouse. Your house is constantly fighting that moisture, and many homes are losing.

The target most indoor-air specialists aim for: 30–50% relative humidity indoors. Below 30% you get dry skin and static; above 50–60%, dust mites thrive, mold risk climbs, and everything feels clammy. Here's why Grand Strand homes struggle to stay in range — and what fixes it.

Where the moisture comes from

• Infiltration. Humid outdoor air leaks in through gaps around windows, doors, recessed lights, and attic hatches. Older beach cottages and raised homes can be especially leaky.
• Ventilation without dehumidification. Bathroom and kitchen exhaust fans remove moisture at the source — but only if they're actually vented outside (many aren't) and only if you run them.
• The AC itself — when oversized. An oversized air conditioner cools the house so fast it shuts off before running long enough to wring moisture from the air. Cool but clammy is the signature of an oversized system. This is why proper sizing matters more than tonnage bragging rights.
• Duct leaks. Return-side leaks in a humid attic or crawlspace pull moisture-laden air directly into the system.
• Everyday living. Cooking, showering, laundry, even breathing add moisture. A family of four can add several gallons of water vapor to indoor air daily.

Why your AC alone may not fix it

Air conditioners dehumidify as a byproduct of cooling — moisture condenses on the cold evaporator coil and drains away. But dehumidification only happens while the system runs. In spring and fall, when it's humid but not hot, the AC barely runs — and indoor humidity soars. That's the season that convinces most people they need a dedicated solution.

Also working against you: thermostat fan set to ON instead of AUTO re-evaporates moisture off the coil between cycles, pumping humidity back into the house. AUTO is the dehumidification-friendly setting.

Fixes that actually work

• Whole-home dehumidifier. Tied into your ductwork, it maintains 45–50% humidity independent of cooling — the definitive fix for chronically humid homes. It also lets you set the thermostat a few degrees higher while feeling more comfortable, which trims the power bill.
• Seal the big leaks. Attic hatch, recessed lights, plumbing penetrations — the usual infiltration highways. Air sealing is unglamorous and effective.
• Fix duct leakage. Sealed ducts stop pulling humid attic air into the system.
• Ventilate correctly. Run bath fans during showers and 20 minutes after; make sure they exhaust outside, not into the attic (depressingly common).
• Right-size at replacement. If your system short-cycles and the house feels damp, mention it when replacing — proper Manual J sizing is a humidity strategy, not just a comfort one.

What about portable dehumidifiers?

They work for a single damp room or basement — but they're noisy, need constant emptying (or a drain hose), add heat to the room, and can't touch whole-house humidity. Think of them as spot treatment; a whole-home unit is the cure.

When humidity becomes a health issue

Sustained indoor humidity above 60% encourages mold growth and dust mites, which aggravate allergies and asthma. If you're seeing condensation on windows, musty smells, or visible mold, the humidity problem has graduated from comfort to health — address the moisture source, remediate the mold properly, and then control humidity so it doesn't return.

How to measure your humidity (properly)

Don't guess — an inexpensive digital hygrometer from any hardware store tells you the truth. For a useful reading:

• Place it in a lived-in room, away from kitchens, bathrooms, and direct sun — not right next to a supply vent.
• Check readings morning and evening for a few days; humidity swings with outdoor conditions and AC runtime.
• Compare rooms. One damp room suggests a local issue (plumbing leak, poor ventilation); whole-house dampness suggests a systemic one (oversized AC, infiltration, no dehumidification).

Sustained readings above 55–60% mean action is needed. And if you're considering a dehumidifier or AC replacement, bring the readings to the consultation — data beats descriptions.