Air Conditioner Not Removing Humidity? Here’s Why

image of high humidity levels depicting why air conditioner not removing humidity

If an AC unit controls only the temperature in your home, it is doing half of the job. An air conditioner helps you beat the heat of summer by lowering the air temperature in your home, but it also provides comfort by lowering the humidity. Even in a house with cooler temperatures, high humidity causes a sticky feeling that makes daily functioning and nighttime sleeping uncomfortable.

An air conditioning unit that is working properly will control both heat and humidity. If it is not, something is not right and should be checked. Before you call an HVAC professional, consider the fact that your solution could be an easy fix that you can deal with independently. If your air conditioner not removing humidity, you only have to check a few simple things to make sure a professional is indeed necessary. Consider some of the more simple reasons your air conditioner is not eliminating the humidity from your home.

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Understanding Air Conditioner Function

Your cooling unit pulls in the warm muggy air in your home and almost magically pushes fresh cool air out through its vents. The science behind this phenomenon is actually quite simple. Inside the unit, there are evaporator coils. These coils are cold, and they absorb the heat from the air that had been pulled in. At the same time, the moisture in the air condenses on the frigid coils. Both heat and humidity have been eliminated using one simple scientific concept we all learned in our early years of school.

Once enough moisture has accumulated on the coils, it drips into a pan designed to catch it and is removed through a drain specifically for that purpose. If something happens to stop or block this process, the air conditioner cannot remove the moisture from the air. The home’s temperature may be lower, but everything will feel damp and humid.

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Risks of High Indoor Humidity

High levels of humidity in a home may not be cause for immediate concern. However, it can do harm over time. Your personal belongings, like books and art, on the walls could slowly deteriorate. The house plants you have nurtured may succumb to the high moisture and slowly die. Your hardwood floors, walls, and ceiling could warp or develop harmful mildew. Mold and mildew thrive in moist areas. They could cause ugly blemishes on your wall and ceiling. Even worse, molds and mildews can pose a health threat to those living in the home.

If you think your air conditioning unit is not removing the moisture from the air, you should act quickly. Here are a few suggestions to look into before you call a professional, in case it is a simple fix.

Air Conditioner Thermostat Setting

image of homeowner adjusting programmable thermostat for air conditioner

This is the simplest check, so it might as well be the first. Look at your thermostat. The fan will have three settings: off, on, as well as auto. You want to have it set to auto. A fan that is simply set at on will run nonstop.

The airflow will constantly be moving over the evaporator coils. This airflow will cause water to evaporate from the coils instead of condensing. Condensed moisture will drip down and be eliminated through the drain. Evaporated moisture will simply be moved back into the house in the cooled air. Without a chance to condense and be removed through the system, this moisture will continue circling around and making you uncomfortable. Set your fan at auto, and it will run when the unit is running. During the off times, the moisture that has been condensed will exit the system and your home as it should.

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AC Unit Evaporator Coils

air conditioner condensing coils

Over time, as air and humidity from the house are flowing over the evaporator coils, dirt may slowly accumulate. If the dirt gets thick enough, it can actually act like a layer of insulation. When the air moves through the coils, the cold that is essential to the operation will be reduced and less effective. This will impact the moisture level as well as the air temperature in the house. The simplest way to deal with this problem is to simply not allow it to happen in the first place.

When you get an annual tune-up for your AC, making sure the coils are clean will be one task the HVAC technician will tend to- a much simpler job than cleaning the coils in the hottest days of summer.

Cooling System Refrigerant

image of an hvac contractor examining refrigerant levels of an air conditioning unit

The coils in the unit are kept cold with a refrigerant. Since it is a closed system, the refrigerant remains in the system and the coils remain cold to do their job. Unfortunately, there may be a time that the system develops a small leak. The amount of refrigerant dwindles and the unit becomes less effective. The house will be humid and no longer cool. You can actually feel warm air coming out of the vents and may be able to hear a slight hissing. A sure sign of a refrigerant leak is a coating of ice on the evaporator coils.

HVAC Ductwork

The cooled air is carried through your home via ductwork. It is not uncommon to find leaks in the ductwork. Sometimes there is a high cost to leaky ductwork, both in comfort and in monthly energy costs. The loss could be as high as thirty percent or even higher. You may find that some rooms feel fine, while other rooms are hot and muggy. This discrepancy could help you determine the general vicinity of the leak. As some of the ducts are difficult to access, a professional may be the answer in this situation.

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Air Conditioner System Size

Bigger is not always better. Your home needs a cooling unit that fits the size of your home. A larger unit will cool down your home very quickly but will miss out on the finer points of your comfort. Cooling the home down faster will not allow time for the moisture in the air to accumulate on the evaporator coils. The humidity will remain high in the home. What’s more, the frequent short cycling of the air conditioning unit will cause harm to its components over time, wearing them out prematurely. A professional with the right kind of knowledge can help you determine what size unit is best for your home.



Humidity and temperature go hand in hand when it comes to the comfort in your home during the summer. The problems mentioned: thermostat fan on, dirty evaporator coils, refrigerant or ductwork leak, or the wrong size system can throw the system off the balance. Homes and belongings can suffer as well as the people living in the house. A professional trained in HVAC can help you get back to the comfort you deserve.

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Lawes Company provides advanced heating and cooling services for residents of Monmouth and Ocean Counties, New Jersey. By working with us, you are assured of a certified technician who is able to provide excellence in HVAC tune-ups, timely repairs, professional installation, and more. All of our techs have the knowledge as well as the experience to service HVAC systems correctly.

Lawes Company guarantees competitive heating and cooling costs. Our maintenance service is sure to improve your comfort, increase energy efficiency and reduce home heating and cooling expense. If you need an HVAC repair or a replacement system, let us recommend the best solution for your home while working within your budget. Our company backs our work with a guarantee to ensure your satisfaction. If you are ready to schedule an appointment, just pick up your phone and give Lawes Company a call. Ask us about our free, in-home estimates.

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