What Should Humidity Be In A House With Air Conditioning?

Most people use air conditioners and dehumidifiers side by side to achieve the perfect indoor climates during the warm season. Although the summers and other warm months are relatively humid, it’s always nice to be prepared in case the moisture levels start fluctuating.

An increasing number of people also keep a dehumidifier just in case the warm weather shows up with excess humidity. The dehumidifier is excellent at removing excess moisture. Indeed, you can even buy a humidifier-dehumidifier combo that automatically detects humidity levels in the home and activates the humidifier or dehumidifier setting as appropriate to raise or lower the humidity levels to the required setting.

Unfortunately, there can be a bit of confusion when you have both the air conditioner and humidifier running. Many people believe that the air conditioner makes the home dry – which is true to a degree because, in the process of removing warm air from the room, the AC may also extract moisture, leaving the room dry.

So, the recommended indoor humidity level for a house with an air conditioning system is 30 – 40% in the winter months. However, depending on your personal preference, it may be even higher up to 50%. At this humidity level, you’ll be able to avoid risks associated with too much humidity and prevent poor indoor humidity.

Worse still, introducing a humidifier into the mix often means you’re indirectly increasing the home’s temperatures. Why? Because moist air has a higher capacity to carry heat. So, now, you have the humidifier introducing more heat into the room, meaning that the AC has to work harder. On the other hand, you also need to humidifier because the AC keeps removing moisture from the space. So, what do you do amid this confusion? How do you balance the two processes?

Below, we evaluate the need for humidification even during the AC season, discuss the relationship between humidification and air conditioning, and recommend a few tips to determine the right humidifier level for optimal indoor comfort.

What is Humidity?

Let’s begin by understanding the meaning of humidity and the role humidifiers play in the home. Humidity is the amount of water vapor in the air. It’s sometimes called absolute humidity to differentiate it from relative humidity. In a nutshell;

  • Absolute humidity: This is the amount of water vapor in the atmosphere, regardless of temperature and atmospheric pressure. To calculate the absolute humidity of a given volume of air (say the air in the home), you divide the mass of the water vapor by the mass of dry air.
  • Relative humidity: This is the measure of the actual volume of water vapor in the air compared to the highest possible amount of water vapor that could be in that air at that temperature. For instance, warm air can hold a lot of moisture. But, the warm air in your home can contain a comparably low volume of vapor. The ratio of actual vs. maximum possible volume of water vapor is what gives the relative humidity.

Related Read: water bottle humidifier

How Low/High Humidity Affects Us

Indoor humidity levels should be maintained in the 30% to 50% range. Otherwise, too high or low humidity levels can be harmful to our health.

Dangers of Low Humidity

Low humidity is expected in the cold season. The cold winter air has a very low moisture capacity. This can cause all kinds of problems, including;

  • Flu and cold symptoms: Low humidity can cause dry sinuses, often resulting in cold and flu symptoms such as coughing and itchy throat. It can also cause a runny nose and slight fevers.
  • Effects on skin: The skin depends on water to remain supple and healthy. As a result, low moisture levels can cause dry, chapped skin, scalp, and lips. It can also worsen skin diseases.
  • Allergy and asthma: Dry air tends to worsen symptoms in people with asthma and allergies. It can also trigger allergic reactions.
  • Effects on furniture and plants: Low humidity levels also cause furniture and plants to lose water, causing furniture to dry and crack and plants to dry up and die.

Dangers of Over Humidification

Too much moisture in the home is just as bad. Although there’s little risk of chapped skin, dry scalp, and drying plants, it can trigger allergic reactions and even cause a few diseases. Some of the safety and health risks of over-humidification are as follows;

  • Mold and mildew: This is perhaps the biggest downside of over-humidification. The excess moisture creates conditions that are conducive for the development and multiplication of mold and mildew.
  • Diseases and other health problems: Mold and mildew both cause diseases. Mold, for instance, is linked to several respiratory illnesses. It can also cause or worsen coughs, allergies, asthma, runny nose, and sinus conditions. Mildew causes wheezing, nasal and sinus congestion. You might need a humidifier for sinus problems.
  • Structural damage: Too much moisture in the home can also compromise the structural integrity of the house. You may even notice cracks in the walls in extreme cases, which can be costly to repair.
  • Damaging paint and wallpaper: Finally, excess humidity can also damage wall paint and wallpaper. Both of these can be expensive to replace.

The above are just some of the risks associated with too low or too high humidification in the home. There are many other risks. You need a humidifier and an air conditioner to achieve the right humidity level in the home to avoid these issues.

How Humidification Impacts the Air Conditioning Process

Unfortunately, the two processes (humidification and air conditioning) don’t get along well when run together.

Air conditioners work by removing warm air from the house, allowing cooler air to come into the home. This is mostly necessary during the summer when indoor temperatures are sky-high. The AC draws hot air from the home, sucks out the heat from the air, then returns the now-cold air to the home while the heat is dumped outside the house. The result is lower indoor temperatures.

However, since this process can also suck out the home’s moisture, many people usually pair the AC with a humidifier to replace the lost water. It’s important to understand that running the humidifier alongside the AC impacts the performance of the AC – negatively.

First off, remember that we’re talking about the warm season when indoor temperatures are very high. You need the AC to bring down the temperatures. Otherwise, the home becomes unlivable. So, you can’t take the AC out of the equation.

But, now, you have the humidifier adding moisture into the home, effectively raising the temperatures in your home. The result? Your AC needs to work harder to remove the extra heat. That’s its job, right? Often, this “working harder” means you need to turn down the thermostat so that the AC runs faster to meet the increased demand. Alternatively, you may feel like getting a bigger air conditioner.

Both “solutions” come with significant downsides.

  • Turning down the thermostat

When you lower the thermostat setting, the AC will run faster. Running faster essentially means that the motor rotates faster. These higher speeds aren’t good for the life of your AC since it causes faster wear and tear.

The result is that your AC is likely to break down sooner, necessitating expensive replacements. Moreover, at some point, the AC will reach maximum speed. What do you when you get there?

  • Buying a higher-capacity AC

Purchasing a larger AC (one that moves a larger air volume per unit time) is an even worse solution. As we’ve seen, ACs are the root causes of the low humidity issues in the summer. They remove moisture alongside the warmth, leaving indoor air dry. Therefore, they are the reason you need humidification in the first place.

So, buying a bigger one only means you’re worsening the problem. You’ll be removing even more moisture from your home. Thus you will need an even bigger humidifier. Talk of a vicious cycle!

So, What’s the Solution?

It all comes back to finding a balance. Otherwise, you’ll keep buying new appliances (humidifiers, ACs, dehumidifiers, etc.) with little benefit.

Keep in mind that the goal is to achieve a balanced indoor climate where it’s cool or warm enough, depending on the season, and you’re getting sufficient moisture in the room. Professionals recommend 30% to 60% humidity. Never compromise on this. As we’ve seen, too low (below 30%) and too high (over 50%) humidity are bad for you and your family’s wellbeing as well as the health of your home, furniture, pets, and plants.

However, you want to keep the setting toward the lower regions of the recommended range. A good setting would be anywhere between 30% and 35%. This way, you’re adding just enough moisture to replace the humidity lost to air conditioning without introducing too much heat to the home.

Alternatively, consider AC systems that are paired with humidifiers. These systems work like a charm because the AC and humidifier settings are adjusted together to create the best indoor conditions. Check out the advantages and disadvantages of air conditioning


Finding the right balance in indoor air conditioning and humidification can be tricky, given that each process undermines the gains of the other. The AC makes the humidifier’s life harder and vice versa. However, as long as you understand each process’s purpose and what really makes the perfect indoor climate, you can always strike a compromise and find that elusive holy grail.

Related posts:

Can You Put Hydrogen Peroxide in a Humidifier?

How Many Humidifiers Do I Need for My House?

Can You Put a Humidifier Next to your Bed?

Will a Humidifier Help Dry Skin? All You Need to Know


Photo of author
Melanie Mavery is an aspiring HVAC technician who is fascinated by the trends and opportunities in the HVAC industry. She spends most of her day writing content on home improvement topics and outreaching to prospects.  She's always looking for ways to support HVACs!

3 thoughts on “What Should Humidity Be In A House With Air Conditioning?”

  1. It’s a shame you don’t have a donate button! I’d most certainly
    donate to this fantastic blog! I guess for now i’ll settle for book-marking and adding your RSS feed to my Google account.

    I look forward to new updates and will talk about this site
    with my Facebook group. Chat soon!

Comments are closed.