What Should Humidity Be In A House With Air Conditioning? Humidity 101

Air Conditioning, Indoor Air Quality

If we are talking about great home comfort in hot weather, cooling is no longer the singular focus. The equally essential concern is your home should have the right humidity level. Humidity plays a huge role in how pleasant we feel at home and how the indoor climate affects our health and well-being.

The good news is that the advent of air conditioning conveniently solves both these problems of heat and indoor humidity. 

But what should humidity be in a house with air conditioning? Is there an ideal humidity level? What are the factors to consider in reaching the perfect humidity level in a home with air conditioning? 

Read on to discover the answers and find the best ways to maintain the optimal humidity level in your home.

what should humidity be in a house with air conditioning

What Is the Ideal Humidity Level for a House with Air Conditioning?

The ideal indoor relative humidity should be between 40% to 60%. During the air conditioning season, it will gravitate toward the higher end of that range, 50% to 60%. In the winter and with a humidifier running, you’ll be on the lower end of that scale.

Relative humidity refers to the percentage of water vapor currently in the air compared to the maximum amount of moisture at a given temperature. The higher the percentage, the more uncomfortably hot you become because sweat does not evaporate easily.

Air conditioning can both cool and lower the humidity as it operates. However, various factors impact the ideal humidity in your home and may compromise the ability of your AC to manage indoor moisture, such as: 

  • Climate and outdoor conditions
  • Building materials and insulation
  • Occupancy levels
  • Activities that generate moisture

Factors that Influence the Ideal Indoor Humidity

While the concept of humidity seems pretty simple to understand–the amount of water that turns into gas present in the air–various factors affect how high or how low it will be in specific homes. 

In this article, we will discuss at least four of those factors so you may have a better understanding of how your indoor comfort works. You can also glean from the succeeding sections how you can optimize the use of your home’s HVAC to better control humidity.

Climate and Outdoor Conditions

Where you live primarily sets the baseline of what you should expect the humidity level will be in your home. 

Locations near oceans and lakes will likely have higher humidity levels. This is easy to understand since in places closest to great bodies of water, there is more water available to evaporate and turn into moisture. This is the case with Florida with a territory consisting of 75% coastal areas. As the air moves across the warm waters, it gathers heat and humidity and brings it to land.

The state of Louisiana comes in a close second to Florida having one of the highest relative humidity in the country. The culprit is the Gulf of Mexico, an ocean basin landlocked by the North American continent. The winds from the south blow over the Gulf and bring an enormous amount of muggy and warm air.

So if you live in these places, your air conditioner must be at a high capacity to fight off some pretty high moisture levels year-round.

Building Materials and Insulation

If the state where you live is not the problem with why it is so humid indoors, you better look into the makeup of the home you reside in. 

If your home often has foggy windows, condensation on random surfaces, peeling paint, and a persistent mildew odor, it may have been built with materials that cannot withstand the heat and humidity.

For example, wood is a popular choice for houses in warmer climates. But since wood also absorbs moisture, you may have to deal with wood warping or deformity. Wood in an extremely humid environment can also trigger mold growth which triggers unrelenting allergies. Construction experts recommend going for engineered wood for a more durable and condensation-resistant type of wood.

Concrete is another good option for construction materials but only if you have proper air circulation indoors and moisture control already in place. Cracks, vents, open windows, and other unplanned openings may otherwise introduce moisture to the concrete and damage its integrity.

But if you moved into a house that is already built, spray foam insulation applied to your attic, walls, and roof may be your best bet in achieving the ideal humidity level. The right choice of insulation materials can make your home airtight, ideal for HVAC system purposes.

Occupancy Levels

Do you ever wonder why a room full of people feels immediately muggier than that with fewer people in it? Because people do increase the humidity level in a room.

An average person who does not exert much energy, maybe just sitting around quietly, already generates 105 watts of heat. Depending on the activity, the heat one person can release can even reach up to 1,050 watts!

But if that person starts talking, he also releases H20 and carbon dioxide into the air. If you multiply this combination of body and H20 from saliva expulsion to 10 or 20 people in the room, the result is a speedy rise in humidity.

Well, air conditioning with the right capacity can combat such an increase in moisture level due to occupancy issues. But if your AC is not properly sized and is way too small for the room, the comfort and well-being of those occupants will suffer immensely as the number of people swells.

Indoor Activities That Generate Heat and Humidity

Believe it or not, you could be your own worst enemy when it comes to increased humidity levels. Some activities that you do inside the home somehow escalate the evaporation of water into your home’s air.

Here are some examples of indoor activities that generate heat and humidity more than you realized:

  • Cooking. The formula for water vapor is water exposed to heat. So every time you cook, especially when boiling water, increases the moisture level in the air.
  • Showering with warm water. The steam from the bathroom as you shower generates a lot of extra moisture. As it touches the cold surfaces of the room, humidity rises.
  • Growing plants indoors. Plants go through the process of evapotranspiration, where plants release 97% percent of the water they took in. The excess water from the soil and leaves result in higher humidity.
  • Line-drying clothes. Some prefer to air-dry their clothes rather than putting them through the dryer to protect the fabric but unknowingly add moisture to the air. The evaporation of the water from the clothing makes the air in your home damper.
  • Making use of humidifiers. A humidifier is helpful to a person with respiratory issues and skin ailments when the air is too dry. But leaving the humidifier on when the air is already muggy is counterproductive.

How Humidity Impacts Home Comfort

We already discussed a lot about what influences indoor humidity in the earlier sections, but maybe we need to take a step back and touch on some basic information about this natural phenomenon.

Humidity is simply the amount of water vapor in the air. What quickly comes to mind when hearing the term “humidity” may be in percent form as it is often used in weather reports. But in reality, there are other categories of humidity you should know about. 

Absolute Humidity

This refers to the actual amount of moisture in the air but not taking into account the temperature of the room. It is expressed in grams of water vapor per cubic meter volume of air (g.m-3). If the amount of water vapor present in the air is high, the absolute humidity is also high. Some scientists deem absolute humidity as a less helpful tool in measurements as many factors can affect its results.

Specific Humidity

Absolute and specific humidity may be quite similar in concept but specific humidity measures the weight of water vapor per unit weight of air. It is expressed in g.kg-1  and is referred to as the most reliable measurement of humidity.

Relative Humidity

This is the category of humidity that we are very familiar with. It is shown with the percent symbol in thermostats and news broadcasts. But why in percentage? 

Because relative humidity, as its name suggests, is the ratio or relationship between the amount of moisture in the air at a given temperature to the maximum moisture air can withstand at the same temperature. In simpler terms, it is the amount of moisture relative to the temperature. 

A dramatic increase in relative humidity affects our feeling of comfort in a space. It can also impact our health negatively as high humidity can lead to fatigue, dehydration, heat exhaustion, muscle cramps, fainting, and even heat stroke.

Constant high levels of moisture in the air can also damage the integrity of a house’s structure. Mold and other pests can also propagate if you don’t keep humidity in check. Mold allergies and infections due to bacteria and viruses can be averted if the water vapor level stays within the 40% to 60% range.

What is the Role of Air Conditioning in Humidity Control

The primary function of an air conditioner is to remove the heat from your home. But its cooling process has a happy byproduct of also removing the excess dampness. How?

As the AC is turned on, it sucks in the warm air from the room and moves it across coils containing refrigerant, a chemical cooling compound that transitions heat and moisture. The moisture is condensed as it makes contact with the cold coils and drains away. Meanwhile, the heat is released through the air conditioner’s outdoor unit.

With this process happening many times over, the resulting air will be cooler and drier than it originally was.

Tips for Maintaining Optimal Humidity Level in Your Home

If you wisely choose an air conditioner that can take on the level of humidity in your local climate, the structural materials and insulation of your home, the number of people who live in your house, and the activities that may increase moisture level, then you are on your way to having an ideal indoor humidity.

But what else can you do to make the most effective use of your air conditioning in managing humidity? Here are some tips:

Tackle the Source of Excess Moisture

As touched on earlier, unwanted openings in a house can compromise the capability of your AC to reduce moisture. Find the leaks around the house that let in the extra heat and the gatecrashing humidity and address them asap. Otherwise, your air conditioner will work so hard but fail to keep the cool temperature and low humidity levels maintained.

Install a Whole House Dehumidifier

Even though air conditioners have dehumidification power, their main job is cooling the air. The AC may not be able to stand a chance if all the four factors mentioned above have a high impact on your home environment. 

The installation of a simple room dehumidifier may help alleviate some of the pressure from your air conditioner in removing excess humidity. But if you want to go big and invest in a whole-house dehumidifier to be added to your HVAC systems, you will be doing yourself a favor and be efficient in managing the humidity in your entire home at a lower cost. A whole-home dehumidifier can also be controlled via a smartphone, making it less stressful compared to maintaining multiple dehumidifier devices.

Regularly Maintain Your Air Conditioner

Your air conditioner is your best friend that can get you through the hottest and most humid weather conditions. As with any good friend, take care of your AC not just when it requires a repair, but routinely and without a fail. 

Make sure you contact a qualified HVAC technician to perform regular cleaning, service, and annual maintenance of your system. Don’t ignore minor repair issues as they may lead to major problems over time if neglected.

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