How to Use an Air Conditioner to Control Humidity

By Rowan Guthrie

June 20, 2024

Nothing’s better than relaxing at home with cool air washing over you on a sweltering summer day. But did you know your air conditioner does more than battle the heat? In the background, it also fights against high indoor humidity.

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Can an Air Conditioner Effectively Control Humidity in Addition to Cooling the Air?

The short answer is yes. In addition to its main job, your AC also acts as a dehumidifier, pulling moisture out of the air and cooling it down.

Here's the science behind it: Warm air holds more moisture than cool air. As the air passes over the cold evaporator coils in your AC unit, the moisture condenses on the coils like dew forming on glass. This condensed water then drains away, effectively removing moisture from your home's air.

However, your air conditioner’s effectiveness in controlling humidity depends on several factors. We cover these in the following sections to help you optimize your AC for peak comfort.

What Is the Ideal Humidity Level for Indoor Comfort, and How Can an Air Conditioner Help Achieve It?

According to the Environmental Protection Agency, the ideal indoor humidity level falls between 30% and 50%. When humidity levels rise above 50%, the air starts to feel muggy and uncomfortable. It can also exacerbate allergies and respiratory problems. Conversely, very dry air (below 30% humidity) can irritate skin and eyes.

By removing moisture from the air, your AC helps you achieve that comfortable sweet spot between 30% and 50% humidity. This not only makes your home feel more pleasant but can also contribute to better indoor air quality, especially for people with allergies or asthma.

What Settings Should You Use on Your Air Conditioner to Optimize Humidity Control?

There are a few key AC settings that can significantly impact its ability to control humidity. Here's how to adjust them for optimal results:

Fan Setting

Most air conditioners offer two fan settings: Auto and On. Here's the crucial difference:

Auto: This is the preferred setting for humidity control. In this mode, the fan only runs when the compressor is active, cooling the air. This allows the condensed moisture on the evaporator coils to properly drain away, preventing it from being recirculated back into your home's air.
On: Running the fan continuously can hinder humidity control. With the fan constantly blowing, the cool, dehumidified air mixes with the condensed moisture on the coils, potentially blowing some of that moisture back into your home.

Temperature Setting

While it might seem logical to set your thermostat as low as possible to remove more moisture, there's a catch. A very cold setting can cause the evaporator coils to become too cold, leading to a condition called coil freeze-up. This not only reduces your AC's efficiency but also hinders its ability to remove moisture. According to the Department of Energy, you should set your thermostat to around 68 degrees Fahrenheit in winter and 78 degrees Fahrenheit in summer. This allows for efficient moisture removal without risking coil freeze-up.

Bonus Tips

Regular air filter maintenance: Change your air filter regularly as recommended by your AC manufacturer, because a clogged filter restricts airflow over the evaporator coils.
Clean coils: Dirty evaporator coils can also hinder the ability to remove moisture, so consider scheduling a professional cleaning of your AC unit's coils every few years, especially if you live in an area with high dust or pollen levels.
Consider a dehumidifier: In particularly humid climates, your air conditioner might struggle to keep humidity levels in check, so a standalone dehumidifier can be a valuable addition to your home.

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Final Considerations

While your air conditioner can be a powerful tool for humidity control, it's important to remember there are limitations. In extreme cases of high humidity, your AC might not be enough. Additionally, some older AC units might not be as efficient at dehumidification as newer models. If you're experiencing persistent humidity issues, consult an HVAC professional. They can help diagnose the problem and recommend solutions. You should be prepared for one of these solutions being a system upgrade if your current unit is nearing the end of its life.

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