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High Humidity Despite Running AC: Causes and Solutions

When your AC cools but humidity stays high, these issues are likely to blame.

Mike ChenAugust 1, 20246 min read

How AC Dehumidifies

Air conditioners remove humidity as a byproduct of cooling. Moisture condenses on cold evaporator coils and drains away. This process requires adequate run time.

Oversized AC Problems

An oversized AC cools quickly but doesn't run long enough to dehumidify. Short cycles leave humidity high even when temperature is reached.

Fan Settings

Running the fan continuously (ON vs AUTO) can reevaporate moisture from coils. Keep fan on AUTO for better humidity control.

Single-Speed Limitations

Single-speed ACs either run full blast or off. Variable-speed units run longer at lower capacity, removing more humidity per cooling cycle.

Leaking Ductwork

Leaky supply ducts lose cool, dry air. Leaky return ducts bring in humid attic or crawlspace air. Duct sealing improves both temperature and humidity.

Supplemental Dehumidification

For persistent issues, whole-house dehumidifiers integrate with HVAC systems. They control humidity independently of cooling.

Frequently Asked Questions

Quick answers to common questions

40-50% relative humidity is comfortable and prevents mold. Below 30% causes dry skin and static; above 60% encourages mold.

Yes, for individual rooms. For whole-house issues, integrated dehumidification is more effective and energy-efficient.

Related topics:

high humidity AChumid houseAC dehumidification

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