Why Is My House So Humid With The AC On? (Find Out Now!)

Why Is My House So Humid With The AC On

A high humidity level during spring or summer with the air conditioning system running indicates problems with your HVAC system. An HVAC professional can quickly inspect your unit and address the appropriate humidity cause. This returns your HVAC unit to proper performance and ensures you have a more comfortable indoor environment during the hottest parts of the year.

Your home’s high humidity levels indicate one of two problems with your air conditioning unit. It either has frozen evaporator coils, disabling them from properly functioning, or the AC’s air filter has become clogged with debris, dirt, and dust.

Reasons Why Your House Might Be Humid

1. Relative Humidity

You’re probably familiar with the phrase relative humidity from the weather forecasts, but do you know what it means? The phrase relative humidity refers to the amount of water vapor in the air. Water vapor refers to the gaseous state of water. It is expressed as a percentage. When outside, a lower percentage of humidity indicates a dry day, while a high humidity percentage indicates potential precipitation.

2. Frozen Evaporator Coils

Inside your air conditioner, a cold evaporator coil works to cool the hot air in the home. Sometimes, it has to overwork and in the cooling process, water condenses on the evaporator coil which then freezes. This frost on the coils stops them from working properly.

When working properly, the evaporator unit draws the liquid refrigerant from the unit outside the home to cool the warm interior area, then expels it through the vents. Once they freeze, the coil can no longer dehumidify the air as it should.

3. Dirty Air Filters

Air conditioners, like other mechanical systems, get dirty. An AC unit includes an air filter that traps most of the dirt and debris in the air pulled into the system for cooling. That keeps the dirt from blowing back out of your AC once it cools the air.

It also means that your air filter needs to change on a regular basis. The air filter also blocks the debris and dust that could otherwise build up on mechanical components.

Making Further Improvements to Home Humidity Levels

You can also improve your home’s humidity levels after the repair visit by doing four things. First, set your thermostat’s fan setting to “auto”. Second, use a whole-house dehumidifier while running your AC to further reduce moisture in the air. These typically come with an LCD readout that apprises you of the percentage of humidity in the home. Third, use a free-standing dehumidifier. And finally, have an HVAC professional install a thermal expansion valve (TXV) or simply check the system’s refrigerant charge.

1. Your HVAC Unit and Humidity Inside the Unit

You can’t totally rid your HVAC unit of humidity in the unit since it comprises part of the cooling process. It must remove moisture from the air to produce cooler air. The process creates water as a byproduct which is why HVAC units have a drain that dumps water outside the home. Your air conditioning unit can produce up to nine gallons of water per day.

It does not take long for your AC unit to dehumidify the air in your home. Your HVAC should need to run for about 15 minutes before it starts to reduce the home’s humidity. It will start reducing the temperature immediately.

2. HVAC Systems with a Built-in Dehumidifier

While all HVAC systems remove some humidity from the home, some units also include a dehumidifier. All air conditioning units remove some moisture from the air during the process of cooling the hot air. Some air conditioners also have a dehumidifier built-in, and these types remove significantly more moisture from the air.

You need an AC that pulls out enough moisture to keep the air healthy, but not too dry. If your unit does not include a built-in dehumidifier, you can purchase a freestanding unit.

You might get tempted to try running the fan all the time, but this will not alleviate the problem. You needlessly run up your electric bill if you run your fan all the time. Set the fan to “auto” for optimum energy-efficiency. The HVAC fan should only run when the system is cooling to result in optimum dehumidification.

3. Reducing Humidity Until HVAC Professionals Arrive

You needn’t suffer while waiting for the neighborhood HVAC personnel to arrive. You can temporarily reduce the home’s humidity by running the exhaust fans in the home. You can also use a free-standing dehumidifier.

If your humidity reaches 65 percent or higher while running the dehumidifier, try moving some potted plants inside. They will absorb humidity and the moisture helps them grow. Temporarily take colder showers and shorten their length.

4. Hire a Professional

You can easily rectify these problems by calling a professional HVAC service. They can help you restore a normal humidity level in your home of between 30 and 50 percent. You should change your AC filter monthly. In areas of blowing dirt outside or dusty conditions, you may need to do this more often.

Whether it experiences humidity issues or not, you should have an HVAC service performed on your AC system at least once per year. You can have the HVAC service personnel show you how to replace the air filter yourself.

When you DIY this activity, you can save yourself money, and you can check the HVAC unit more frequently for dust and dirt. That helps you keep the air in your home cleaner as well as improving its humidity levels.

A Bad Smell Indicates Mold

Of course, if you notice your home starting to smell musty or funky, you need to cut off the culprit. You need to find the mold and mildew and treat the problem. You need to find the source of the mold or mildew and have a professional abatement service sanitize and sterilize the area. This may require removing wallboard and two-by-fours from the wall framing (the studs).

The abatement service then remediate the source and kills the mold and mildew. They replace the wall studs, so your wall continues to be as sturdy as always, and then they replace the wallboard and repaint it to match your existing wall color. Only by doing this can you get rid of the smell and the health hazards.

Related Questions

What happens if the air in your home becomes too dry?

When the air becomes too dry and the humidity drops below 30 percent, you and the other individuals and animals in your home may experience trouble breathing. You will wake up feeling stuffed up since your nasal passages will get too dry.

What causes humidity in the home?

  • Using foam insulation in the attic can also increase a home’s humidity. This can allow too much moisture into your duct system.
  • You might have leaky ducts. That would pull hot, humid air from your home’s attic or upper crawl space into the ductwork and into your home.
  • Your kitchen fans above your range and oven might be pulling in attic air. Your poor AC just can’t keep up!
  • You can address this problem by inspecting your attic and sealing it properly. Also, have the ductwork checked for leaks.
  • Install a dehumidifier in the attic and run it continuously.
  • Add to your home’s ductwork or re-route the existing ductwork, so the attic receives air conditioning, too.

Is it possible that only one or two rooms get too humid?

This can easily happen. If your home has leaky ductwork in the room that gets too humid or muggy, you need to have the HVAC personnel fix the leak. The leak lets air from the attic mix with that from the outdoors and the room itself. Your ductwork design could also have been improperly designed and installed. Improperly zoned ductwork creates the same problem as leaky ductwork.

Some installers do not run ductwork to the basement, the moistest environment in the home. This accounts for the extremely high humidity in most basements.

How do you find a reliable professional HVAC repair service?

Word of mouth still provides the best referrals, so start by phoning family and friends in your local area to ask who they have used in the past. Once you have a shortlist, check out each business on the Better Business Bureau site and Angie’s List. This lets you read how others found each company’s service to perform. Obtain quotes or estimates from the best three services. Choose the lowest-priced service of the three highest quality providers.

Upgraded Home Team

We are a team of homeowners and home improvement enthusiasts who enjoy sharing decorating, gardening, home improvement, and housekeeping tips with other homeowners! Whether you're looking for advice on furnishing your living room or the next outdoor DIY project, we've got you covered.

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