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Fully Explained: Does AC Reduce Humidity Levels?

High humidity is detrimental to your home construction, insulation, moisture-sensitive equipment, and even your overall well-being. Running an air conditioner during hot and humid weather can help reduce humidity levels in your home and improve air quality to tackle these issues.

Does AC Reduce Humidity 01

In simple terms, air conditioning is the process of creating and maintaining certain temperature levels, relative humidity, and air quality indoors. It removes excess heat and moisture by taking the warm air into the system and disperse cold air. This is why it is important to install air conditioning in homes and offices since increased levels of moisture lead to mold growth and pollute indoor air.

So, I've curated a guide to help you understand how an air conditioning system can hemp reduce humidity. Read on.

Understanding Humidity

Understanding Humidity

Humidity, often referred to as relative humidity, is the concentration of water vapor present in the air. Water vapor, in scientific terms, is water in its gaseous form, which is invisible to the human eye, yet we feel in terms of how ‘sweaty’ we are or how ‘wet’ the climate feels.

While mild humidity is mostly harmless except for the discomfort it causes, excess humidity can be detrimental to people with respiratory illnesses like asthma, bronchitis, COPD, pneumonia, etc.

We usually use relative humidity (a ratio of absolute humidity to maximum humidity present in the air, measured in percentage) to determine the weather and chances of precipitation. When relative humidity exceeds 50%, moisture-related issues such as poor insulation and mold growth may occur. Especially in winter, you should ensure humidity levels are low to prevent condensation and damage to the construction and insulation of your home.

Factors That Affect Humidity

Two main factors affect the relative humidity in the air: temperature and pressure of the system of interest. As the temperature rises, the moisture levels in the air also increase. Likewise, the relative humidity drastically reduces in cold temperatures as the moisture condenses.

Moreover, relative humidity is indirectly proportional to the air pressure. So, when there’s an increase in air pressure, the moisture levels decrease gradually. That’s why it’s more difficult to keep your upper floors cooler on a hot day since the air pressure decreases with elevation.

Effects Of High Humidity

High humidity levels can harm the human body and air conditioning systems more than dry air. Some of its effects are as follows:

1. Overheating Of The Body

Surprisingly, excess humidity fools the body into thinking the temperature is high. This makes your body produce excess sweat to cool down and may often lead to heat exhaustion or stroke. That’s why many medical practitioners recommend not staying outdoors for prolonged periods in summer and having a dehumidifier or AC unit with a dehumidification feature at home.

2. Asthma And Allergy Symptoms

If the indoor humidity of your home is high, your existing respiratory illnesses will worsen. You’ll likely experience symptoms like difficulty breathing, panic attacks, headaches, violent coughs, sinus infections, etc. But putting the air conditioner on when there’s extra moisture in the air can help prevent this.

3. Excessive Sweating

As mentioned before, high humidity will trigger your body to produce sweat. At the same time, the increased levels can prevent efficient moisture evaporation, so the sweat will remain on your body, making you feel uncomfortable.

4. Damaged Equipment

Excess moisture is known to cause damage to mechanical equipment and temperature-sensitive materials. Anything that runs on motors, pistons, or any movable technology can be affected by moisture - this is especially true when it comes to an AC system. HVAC specialists also agree that high humidity can affect the efficiency of air conditioners and increase energy bills even though they can remove humidity.

5. Mold Growth

If you have high indoor humidity levels, there is a high chance that your home will develop mold and mildew. Indoor mold growth can affect your home’s insulation and absorb cool air, making it difficult for your cooling system to achieve the set temperature. This is why energy bills run high in places with excess heat and humidity, even if the frequency of AC operation is relatively lower.

Moreover, areas like the bathroom and kitchen are more susceptible to mold growth, as they have higher relative humidity.

Signs of High Humidity

There are common signs that will help you determine whether your indoor humidity is high:

  • Condensation on windows in the form of water droplets or fog
  • Excess mildew in the bathroom, kitchen, ceilings, or walls
  • Mold growing on surfaces like closets and basements
  • Cracking, blistering, or peeling paint on the exterior or interior of the house
  • Dust mite population, which causes dust allergies and respiratory problems
  • Musty or moldy smells in your home

Having an air conditioning system running is, therefore, extremely important in areas with high humidity. Even though air conditioners need to work longer to reduce humidity, they can go a long way in preventing damage to your home’s structure, material, and insulation.

So, investing a little more in your energy bills on hot, humid days can actually save you renovation expenses in the long run! Further, there’s no point in compromising indoor air quality since it can directly affect your physical well-being.

How Does An Air Conditioner Work?

Before trying to understand how an air conditioner removes humidity in your home, it is important to understand how it actually works.

An air conditioner lowers the temperature, right? But how does it do it? Well, the warm, indoor air from the room is first sucked through the grilles located on the lower side of the machine. This air moves through chiller pipes filled with a refrigerant that helps to cool it down.

The air then passes over an evaporator coil which contains a cooling agent circulating throughout the air conditioning system, changing from its liquid to gaseous form or vice versa when required. When the air passes over it, this cooling agent absorbs the heat and moisture - this is where a heat transfer takes place. After this absorption is complete, the excess condensation drips onto the condensate pan beneath the coil.


Remember to clean out the condensate pan frequently to avoid the chances of the moisture evaporating and going back into the indoor air.

Then, this air passes over a heating element, which, when turned up during winter, produces more hot air, making the AC unit act as a heater. However, this feature might not be available in all portable AC units, so check the product description if you’re going for this type.

Then, an AC fan blasts this air into the room through another grille or duct. If the heating element is turned down, the incoming air is much cooler, and the cooling cycles are more efficient. Similarly, the higher the set fan speed, the faster the incoming air will be projected into the room. Thus, the fan speed determines how fast the room will be cooled down or heated.

So, as you can easily understand, an air conditioner can both cool and remove humidity in your home, thereby improving indoor air quality.

Does AC Reduce Humidity?

As already discussed, air conditioners lower humidity using their evaporator and condenser coils. The refrigerant that cycles between indoors and outdoors facilitates the functioning of an air conditioner; however, its main function is to cool the indoor air while the fan cycles it into the room. And the fact that air conditioners lower humidity is rather a side-effect of the condensation process.

Since the indoor coils are very cold, more moisture from the indoor air condenses on them. The moisture then condenses into water, which is expelled through a drainage hose, condensation tank, or air exhaust hose (depending on the air conditioner type). This cycle continues for some time and effectively lowers the indoor humidity levels in your home.

How Much Humidity Can Air Conditioners Remove?

An air conditioner is mostly purchased for heating, ventilation, and air conditioning; however, it can also control humidity levels. This feature is known as dehumidification, and you can check the ‘dehumidification rating’ on the specifications sheet of an air conditioner. Expressed in Pints per hour (Pt/h) on the specs sheet, it tells you how much humidity your AC unit can extract from the air per hour.

For example, if a 1400 BTU AC unit has a maximum dehumidification rate of 4.0 pt/hr, then your unit can, in ideal conditions, extract more than 100 pints (or 15 gallons) of water from the air per day. Long story short, you can avoid purchasing a separate whole-house dehumidifier if you invest in a high-quality AC system.

Benefits Of Reducing Humidity

A. Improved Indoor Air Quality

Since humidity constitutes condensed water vapors, it allows dust and debris to cling to the water droplets, thereby lowering indoor air quality. What’s more, high humidity levels can absorb harmful chemicals from home appliances and materials, increasing pollution. 

Running an air conditioner in dehumidification mode can help reduce humidity and eliminate these pollutants. This will also make your home environment unfavorable for pests like cockroaches, silverfish, spiders, etc. So, besides reducing mold and mildew formation on your walls and providing cool air, low humidity can reduce the chances of pest infestations and damage to your home insulation. 

B. Health Benefits

The various health issues that come with high humidity are the number one reason I prefer to run my air conditioning system to remove moisture, even if it’s cold outside.

Low humidity levels will help you cope with several respiratory diseases, including asthma, COPD, pneumonia, etc. Since a designated dehumidifier or AC removes humidity and prevents mold and bacteria, there’ll be fewer triggers in your home that can worsen these symptoms.

Moreover, lowering the humidity level can help manage skin diseases such as acne, eczema, and psoriasis, which are easily triggered in hot and humid conditions. All in all, a balanced humidity level has several health benefits.


If your air conditioner has a clogged filter, its dehumidification capacity and ability to remove impurities from the air reduces significantly. That’s why I recommend cleaning the AC filter thoroughly at least once a month to maintain good indoor air quality.

C. Increased comfort

Of course, if the indoor air is clean and you reap health benefits from it, your comfort levels will also increase. Not having to deal with pest infestations and moldy walls can eliminate a lot of hassle regarding pest control and renovations. Moreover, having low humidity levels can make your home more comfortable for children and pets. 

Generally, your home will feel more comfortable at humidity levels ranging from 30 to 50% . You can measure this level using a thermostat with humidity control to help set the AC at the right temperature or setting.

Other Ways To Reduce Humidity

Running the air conditioner is usually sufficient to bring down the humidity levels below 50% in humid climates. However, if the cooling system still seems to be insufficient in case of extreme humidity, here are some other ways through which you can tackle the problem.

1. Proper Ventilation

Running the exhaust fan when you shower, clean, or cook in the kitchen, bathroom, or laundry is important to ensure proper air circulation. Spot ventilation will tackle humidity at its root by reducing moisture in those particular areas. If there's pleasant weather in your area, consider opening all the windows instead to save electricity.

2. Wipe Off Any Standing Water

Any water vapor accumulation on surfaces can contribute to high humidity levels. So, if you see water on kitchen counters, shower tiles, or floors, quickly wipe it off until completely dry to prevent mold and mildew.

3. Adjust the AC Fan

It takes time for your air conditioner to expel the condensation from the evaporator coils - that’s why running the AC fan continuously can direct moisture back into your home. The best way to avoid this is to set the AC fan to ‘auto’ so that it runs only during the cooling cycles.

4. Change the AC Filter

HVAC specialists recommend changing the air filter at least once every month to reduce humidity and maintain indoor air quality. A clogged filter traps dust and debris and often harbors mold and bacteria, if it remains wet for prolonged periods. This, in turn, blows mold spores and humidity into your room, increasing your discomfort.

5. Clean The Evaporator Coil

If your air conditioner is having difficulties reaching the set temperature and dehumidifying properly, the evaporator coil probably needs cleaning. A dirty coil prevents efficient cooling and traps moisture within its system, so it’s essential to clean it regularly. However, don’t try cleaning it yourself and call a professional as  any improper handling can lead to mechanical malfunction or compressor failure.

6. Upgrade Your AC System

If your air conditioner is not able to remove humidity efficiently, it’s time for a replacement. And when purchasing a new AC system, look for advanced features, like a thermal expansion valve (TXV), variable fan motor, dehumidifier settings, etc. While a TXV delivers a specific amount of refrigerant depending on the set temperature, the variable motor facilitates adjusting the fan speed. Both features help improve cooling and dehumidification.

Final Thoughts

Air conditioning is really important to control humidity and maintain optimal temperatures for comfortable living. Besides these obvious functions, using an air conditioner to reduce humidity has several benefits, including mold and mildew prevention, increased comfort, and alleviation of respiratory diseases. 

Even in extremely hot and humid climates, ACs can successfully eliminate excess moisture in the air. However, if an air conditioner is not working for you, there might be some problem with its mechanical parts or air filter. In this case, follow the simple techniques that I’ve mentioned above.

With that, it’s time for me to wrap up. See you next time!