Summer time in the Midwest brings hot days and along with the heat there is something else. We get some humidity as well. The high humidity can make working and playing outside a little uncomfortable. If these dog days of summer have ever made you wonder How Air Conditioners Dehumidify, this blog is for you.

Accurate Heating & Cooling is an established heating and air conditioning contractor in the Omaha metro area. We have been serving our customers for over 20 years. Give us a call today at 402-238-2425 for all your heating and cooling needs. We have an A+ rating with the Better Business Bureau. Check out our Testimonial page to see what our customers say about us! In this blog, we will describe How Air Conditioners Dehumidify.

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The hot humid air of summer will work its way into our homes as well. Older homes have more drafts than newer homes. The small passages around doors and windows can bring humidity inside. And there are sources of moisture inside the home as well. Running the shower adds moisture to the air. Plants release water vapor throughout the day. Pets and people also release moisture. Cooking will add a little to humidity levels as well.

Optimum Indoor Humidity Levels

There is an optimum level of humidity that we find comfortable. It the humidity level is too low then the air is dry. Our skin dries out more. Static electricity can be present. When humidity levels are too high we feel sticky. The air temperature in our home may be fine, but we are uncomfortable. This is from the high humidity.


How Air Conditioners Dehumidify

The good news is that our home air conditioner naturally removes humidity from the air. The a/c unit dehumidifies as it cools the air. We don’t have to adjust any “dehumidify” setting on our thermostat. We don’t have to take any particular action. The dehumidification process happens naturally.

Here is a good way to understand how dehumidification happens. Think about having an ice cold beverage on a hot, humid, summer day. We notice a layer of moisture forming on the outside of the cold glass.

How Air Conditioners Dehumidify - Image of Ice Cold Soda Glass Sweating

When we look closer, we see beads of moisture running down the side of the glass.

How Air Conditioners Dehumidify - Close Up Image of Ice Cold Soda Glass Sweating

While this scene is familiar to us, what is going on here? What causes the moisture from the air to condense onto the glass?

Water Vapor is a Factor in How Air Conditioners Dehumidify

Humidity in the air is in a vapor form. Air can hold a certain amount of water vapor based on the temperature of the air. When relatively warmer humid air comes into contact with the relatively cooler drinking glass, condensation occurs. Some water vapor from the air condenses into liquid water and adheres to the cold glass.

When enough water forms on the surface of the glass, it begins to drip down the side. A puddle forms at the base of the glass.

Condensation is a Factor in How Air Conditioners Dehumidify

This same process happens on the air conditioner evaporator. Here we begin to see How Air Conditioners Dehumidify. The evaporator is a metal coil that is usually located above your gas furnace. The evaporator is encased in a metal cover so it looks a lot like regular metal ducting sitting directly on top of your furnace. There will be two small copper tubes going into the evaporator. The copper tubes carry the refrigerant.

When your air conditioner is operating, the refrigerant makes the evaporator cold. Typical temperatures of the evaporator coil range from 40F to 50F. A little warmer than an iced beverage, but still cool enough to cause water vapor from the air to condense onto the metal evaporator coil. As the air conditioner runs, there is a constant supply of room air that is delivered over the cold evaporator. This means that there is a constant amount of moisture condensing onto the cold evaporator.

The condensed water drips down into a pan under the evaporator. Some type of drain piping connects to the evaporator. This is usually either pvc piping or vinyl tubing. This condensate drain is normally directed to a nearby floor drain. Sometimes a small condensate pump is used to get the condensate to a drain further away.

As a side note, some homes have an electric furnace instead of a gas furnace. Electric furnaces are also called air handlers. The evaporator coil in an air handler is usually located in the bottom of the air handler.


High Humidity Level Support Growth of Bacteria, Mold, and Insects

We obviously want to dehumidify the air to achieve the desired comfort level in our homes. However, there are other reasons to remove excess humidity from the air. The Centers for Disease Control and Prevention (CDC) advises that excessive moisture in the air (high relative humidity) that is not properly controlled with air conditioning can also lead to excessive dampness. Dampness is a problem in buildings because it provides the moisture that supports the growth of bacteria, fungi (i.e, mold), and insects.


Health Symptoms

How Air Conditioners Dehumidify - CDC Logo Image

The CDC also advises that the health of those in damp buildings has been a growing concern through the years due to a broad range of reported building-related symptoms and illnesses. Research has found that people who spend time in damp buildings are more likely to report health problems such as these:

  • Respiratory symptoms (such as in nose, throat, lungs)
  • Development or worsening of asthma
  • Hypersensitivity pneumonitis (a rare lung disease caused by an immune system response to repeated inhalation of sensitizing substances such as bacteria, fungi, organic dusts, and chemicals)
  • Respiratory infections
  • Allergic rhinitis (often called “hay fever”)
  • Bronchitis
  • Eczema

Moisture allows indoor mold to multiply more easily on building materials or other surfaces, and people inside buildings may be exposed to microbes and their structural components, such as spores and fungal fragments. Mold may also produce substances that can cause or worsen health problems, and these substances vary depending on the mold species and on conditions related to the indoor environment. Moisture can also attract cockroaches, rodents, and dust mites. Moisture-damaged building materials can release volatile organic compounds that can cause health problems. So the importance of How Air Conditioners Dehumidify goes beyond simply comfort cooling.

Ventilation Options That Can Reduce Mold and Allergens

The CDC also offers specific guidance on the use of proper ventilation to help maintain the optimum indoor humidity levels. For more information, refer to the CDC website. For homes with allergen issues, there are some solutions that will reduce indoor allergen levels. Installing an Electrostatic Air Cleaner goes a long way towards removing allergen and mold spore profiles. Another option is an air scrubber that uses UV light and Ozone to neutralize these contaminants.


My Personal High Humidity Experience

So here is my personal experience with high indoor humidity levels. Over the years, my older home has benefited from some home improvements. These include added insulation. And also the sealing of window frames. The slow maturing of trees in the yard that help to shade the roof from the direct rays of the sun. The effect of all these things is to reduce the heat load within the structure. The tonnage of the air conditioner has remained the same. What was happening is that the lower heat load caused the a/c to short cycle.

When the thermostat started the a/c on a call for cooling, the a/c would start. But the a/c would satisfy the set temperature quickly after only a few minutes. Then the a/c would shut off. The temperature was cool enough, but the home was not comfortable. The a/c did not run long enough to adequately dehumidify the air. The higher indoor humidity level made it a little uncomfortable in the home. Then it happened to be time to replace my older, less efficient air conditioner. There was starting to be quite a few part failures that were becoming costly and were an inconvenience. Those breakdowns tended to happen at the wrong times.


Further Ways to Reduce High Humidity Levels

There are a lot of advantages that come with upgrading an older air conditioner to a new more efficient unit. Enhanced dehumidification is among them. The evaporator coil in a new R-410A air conditioner is physically larger than the evaporator in my older R-22 system. A physically larger evaporator means that the air flowing across the evaporator coils is exposed to the cool metal surfaces longer. This means that more water vapor in the air has a chance to condense out. Which means better dehumidification.

In the case of my home specifically, the new a/c was a half ton smaller in size as the heat load in the house had been reduced. The new air conditioner runs longer each time a call for cooling is given by the thermostat. However, the temperature fluctuations are much smaller. The air is dehumidified better. And the higher efficiency offers reduced electricity usage. The Trane website offers additional information about new high efficiency variable speed and two stage air conditioners.


Variable Speed and Two Stage Units

To further enhance dehumidification during air conditioner upgrades, we have a few options. The newer variable speed or two stage units dehumidify better because they begin operation with a slower blower speed which allows for the removal of more water vapor from the air.


Related Topics

The warm humid summer months require dehumidification. During the winter months, the opposite condition is often found. The drier cold outside air can lead to drier indoor air conditions. Humidifiers attached to the home’s HVAC system add water vapor to the dry indoor air. The optional home humidifier will raise humidity levels to a comfortable level. A very informative guide on how to manage and understand indoor humidity levels is available here.

Accurate Heating & Cooling can assess your HVAC system and offer options to increase your homes indoor air quality. Give us a call today at 402-238-2425 for all your heating and cooling needs. We also service heat pumps, mini splits, and geothermal units.

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There are some other heating, ventilation, air conditioning, and refrigeration related topics that may be of interest to you. Click here for information on what air filter would be best for your home. There is also information available here on what MERV ratings for air filters mean. For some information on the best way to purify your home’s air, check out this blog on the Air Scrubber.

Does your home still have one of those older mercury thermostats? Check out this link for more information about them. And do you try to do some of your own maintenance to help keep your furnace and air conditioner running all season long? There are some helpful homeowner maintenance tips at this blog that will help.