What is Humidity in an HVAC system?

The amount of moisture in the air is called humidity. High humidity levels can cause discomfort, and low humidity levels can cause static electricity and other problems. Variable speed systems can reduce this moisture for added comfort. By humidity, we mean the concentration of water vapor in the air. The higher the humidity, the more water vapor is present in the air.

There are 2 types of humidity:

  1. Absolute humidity is the actual amount of moisture in the air.
  2. While relative humidity is the amount of moisture in the air compared to the amount of moisture that the air can hold at a certain temperature.

Both indoor and outdoor humidity levels can affect your comfort level. Indoor humidity levels are usually controlled by your HVAC system, while outdoor humidity levels depending on the weather.

What is the best humidity for HVAC?

 The ideal indoor humidity level for comfort and for preventing these problems is between 30% and 50%. Many home humidifiers and dehumidifiers are available to help you maintain this level of humidity. Some HVAC systems also have built-in humidifiers and dehumidifiers to help control indoor air moisture.

Can you control humidity with an air conditioner?

Yes, many air conditioners have a “dry” or “dehumidify” setting that will remove moisture from the air as it cools. This can be helpful in reducing indoor humidity levels on hot, humid days.

How do I lower the humidity in my HVAC?

If your HVAC system does not have a built-in humidifier or dehumidifier, you can use a portable unit to lower the humidity in your home. Portable units can be placed in the room or area that you want to dehumidify.

You can also reduce indoor humidity by:

  • Opening windows and doors to let fresh air in.
  • Using fans to circulate the air.
  • Take shorter showers.
  • Running the exhaust fan while cooking.
  • Venting clothes dryers to the outside.

HVAC humidity problems

Too much humidity indoors can cause problems such as:

  • Musty odors.
  • Water condensation on walls, windows, and other surfaces.
  • Excessive static electricity.
  • Mold and mildew growth.

Too little humidity indoors can cause problems such as:

  • Dry, itchy skin.
  • Static electricity.
  • Dry sinuses and nasal congestion.
  • Cracked or peeling paint.


Humidity levels that are too high or too low can cause problems indoors. Your HVAC system can help to control the indoor humidity levels.

Related Links

Humidity Testers | PCE Instruments

Digital Thermometer Humidity

Relative Humidity vs Dewpoint | WeatherWorks

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