Air Quality
Humidity Control: How Your HVAC System Manages Moisture
6 min read••
Humidity affects comfort and health. Here's how your HVAC system manages it and what to do when it doesn't.
Indoor humidity impacts comfort, health, and your home. Understanding how your HVAC affects it helps you maintain the right levels.
How Air Conditioners Remove Humidity
The Dehumidification Process When warm, humid air passes over cold evaporator coils: - Air temperature drops below dew point - Moisture condenses on coils - Water drains away - Drier air circulates back
Why Some AC Systems Dehumidify Better - Properly sized systems run longer, removing more moisture - Variable-speed systems excel at humidity removal - Oversized systems cool quickly but don't run long enough to dehumidify
Signs of Humidity Problems
Too Humid - Sticky, clammy feeling - Condensation on windows - Musty smells - Mold growth - AC runs but doesn't feel comfortable
Too Dry - Static electricity - Dry skin and eyes - Cracking wood - Respiratory irritation
Bay Area Humidity Patterns
Coastal Areas Generally more humid, especially with fog. Dehumidification matters more.
Inland Areas Lower humidity in summer but can still be high in shoulder seasons.
Winter Heating often dries air too much. Humidification may be needed.
Solutions for High Humidity
HVAC Adjustments - Ensure system is properly sized - Check that AC coil is clean - Verify proper refrigerant levels - Consider variable-speed upgrade
Additional Equipment - Whole-house dehumidifier - Standalone dehumidifiers for problem areas
Behavioral Changes - Use bathroom and kitchen exhaust fans - Limit indoor moisture sources - Improve ventilation
Solutions for Low Humidity
Winter Heating Impact Furnaces don't add moisture—they heat air that's already dry. As cold air comes in and warms up, relative humidity drops.
Humidification Options - Whole-house humidifier connected to furnace - Portable humidifiers - Houseplants (minor effect) - Adjusting heating habits
Ideal Indoor Humidity
Target 30-50% relative humidity: - Below 30%: Too dry, health and comfort issues - Above 50%: Risk of mold and dust mites - Sweet spot: 40-45%
A simple hygrometer helps you monitor levels.