What Is Relative Humidity

Regulating the levels of humidity is one of the most important factors when air quality is concerned. Too high humidity levels can cause mold and mildew growth, and cause further problems with health or home structure. Dry air on the other hand is also not good, since it can irritate your eyes, nose and skin, and also cause structural damage of home or office.

We use several measures to determine the levels of humidity, but relative humidity is used most often. Simply put, relative humidity represents the percentage of water present in the air relative to the maximum amount of water that can be in the same amount of air. To explain relative humidity fully, we’ll need to discuss absolute humidity first, but we’ll come back to this in the next section.

Setting the humidity levels in your home within the optimal range can be done rather easily using a humidifier and/or dehumidifier. In this post, we’ll talk about what is relative humidity, how to calculate it, how humidity levels impact your health and environment, and how to keep it at ideal levels.

What Is Absolute Humidity?

The amount of water vapor divided by the amount of dry air in a volume of air at a given temperature. Higher air temperature means more humidity. We use grams of moisture per cubic meter of air to express absolute humidity.

What Is Relative Humidity?

The mass of water vapor present in the air at a certain temperature relative to the maximal mass of water vapor that air can hold at the same temperature is the measure called relative humidity. It is expressed in percentages. Precisely, the gram per cubic meter measure of water vapor in the air divided by the gram per cubic meter measure of the maximum mass of water the air can contain at that temperature. The result is then multiplied by 100 to get the percentage of relative humidity.

The Environmental Protection Agency (EPA) suggests that the optimal relative humidity indoors should be between 30% and 50%. Levels higher than that can accelerate growth of mold and mildew, and hold on to allergens, which can trigger allergy or asthma symptoms. The impact that higher humidity levels can leave on your home is also negative, since the growth of mildew and mold can be very harmful to walls, floors, windows and furniture. Low levels of humidity can make your skin feel dry and itchy, irritate your nose and eyes, cause chapped lips and fragile hair and more. Dry air can also be harmful for houseplants, and wooden furniture.

That being said it becomes clear how important it is to regulate humidity levels. Relative humidity is a very useful measure that will help you decide whether you need to get a humidifier or dehumidifier, based on the amount of moisture present. We should underline that the geographical location of your home plays an important part in determining the amount of humidity since warmer regions usually have higher humidity levels than colder regions. We can measure relative humidity using a hygrometer, which can be purchased at the hardware store or on Amazon for less than $20. Some humidifiers also come with a hygrometer built-in.

What Causes Humidity Indoors?

Moisture can come inside your home in several ways. Naturally, places in your home where you normally use water, such as the kitchen and the bathroom, usually have higher levels of humidity. The common reasons behind indoor humidity are:

  • Poor ventilation
  • Water leaks in sinks, toilets, pipes, or on the roof
  • Steam evaporated while cooking with poor ventilation
  • Long, warm showers with poor ventilation
  • Excessive use of laundry dryer
  • Rainwater
  • Houseplants

How Humidity Affects Your Home?

Depending on the temperatures outside, the air can contain more or less water. Warmer air is usually more humid. On the other side, colder air can hold less water vapor. In this section, we’ll explain the impact that humidity can make on your home.

How High Humidity Affects Your Home?

Excessive relative humidity levels provide perfect conditions for mildew and mold growth, which can lead to issues such as:

  • Dump, musty smells
  • Misshaped wooden furniture, swelling in floors, window and door frames
  • Problems with electronic devices
  • Stains on ceilings and walls
  • Wallpaper or paint peeling off the wall
  • Condensation on windows

How Low Humidity Affects Your Home?

Dry air on the other side is also problematic. Although its negative effects on your health are more subtle and take more time to be recognized, the way it affects your home is kind of similar to excessive relative humidity levels:

  • Shrinking wooden furniture, doors, and windows
  • Peeling paint and wallpapers
  • Gaps between the ceiling and walls
  • Warping hardwood floors

How Relative Humidity Affects Health?

Humidity is an important factor when it comes to life quality. It can make a significant impact both on your home and your health. In this section, we’ll go through possible health issues related to humidity levels.

How High Humidity Affects Your Health?

Excessive humidity levels in your home can do more damage than “just” destroying your furniture and wallpapers since the air you breathe has a huge impact on your health. This is especially true for people with asthma or those who struggle with different allergies. Anyway, keep in mind that even if your health is generally good, long-term exposure to high levels of humidity can induce issues such as:

  • Irritated nose, eyes, throat, or skin
  • Problems with breathing, including worsened symptoms of allergy or asthma
  • Released Volatile Organic Compounds (VOCs) can induce serious issues such as cancer, damaged nervous system, or eczema
  • Exhaustion

How Low Humidity Affects Your Health?

Long-term exposure to dry air can lead to health issues such as:

  • Dry skin cracked lips, and skin or hair
  • Irritated or inflamed, itchy eyes
  • Nosebleeds
  • Exacerbated symptoms of asthma and allergies
  • Stronger symptoms when you have a cold or flu
  • Body chills
  • Static electricity

How to Regulate Humidity Levels?

As we mentioned, humidity levels vary due to numerous reasons. To prevent possible health risks and structural damage to your home, you’ll want to do your best to keep relative humidity within the optimal range between 30% and 50%. Fortunately, there are ways to balance your humidity levels quite easily. Depending on the region where you live, using a humidifier or dehumidifier can do most of the work.

What Is a Humidifier?

The main purpose of humidifiers is to release water vapor into the air and so increase relative humidity. If you follow the manufacturer’s instructions, a humidifier can improve your air quality significantly. Humidifiers can release cool mist, hot steam, or both. The types of humidifiers are:

  • Central (or whole home) humidifiers: built-in your venting, heating, or air conditioning system; release cool mist; expensive, but offer a long-term solution;
  • Evaporators: release cool mist into the air using a fan, budget-friendly
  • Impeller humidifiers: disperse cool mist thanks to the fast rotating discs, budget-friendly
  • Steam humidifiers: Most portable option; use electrical power to warm and then cool water to create steam
  • Ultrasonic humidifiers: Use ultrasonic vibrations to produce both cool and warm mist

It’s important to note, that, depending on your geographical location or season of the year you might need to consider purchasing both a humidifier and a dehumidifier.

What Is a Dehumidifier?

A dehumidifier is a device whose main goal is to remove excess moisture from the air. This process makes your space much less attractive to mold, mildew, and dust. If used properly dehumidifiers can be of great help when balancing your humidity levels and improving the air quality at your home or office. Based on how they work, they can either be refrigerant (compressor) or desiccant.

  • Refrigerant or compressor dehumidifiers: Use the fan to draw the air inside the dehumidifier, uses cold coils to cool the air down and collect condensed water, then release dry air back into the room;
  • Desiccant dehumidifiers: Use sorption materials placed in a slowly turning rotor to remove the moisture from the air, might require more energy than refrigerant ones;

Keep in mind that both humidifiers and dehumidifiers can also be of great help when removing dust mites, VOCs, bacteria, and other stuff we want to avoid from the air.

Final Words

This concludes our pretty comprehensive post that answers what relative humidity is, how it affects your health and home, and how to handle it. Keep in mind that the ideal humidity level is between 30% and 50%, and try to maintain it within that range.

We hope you like the article and found it to be educational. In case you have any questions about the subject, feel free to post a comment and we’ll be happy to provide you with an explanation. Good luck with balancing relative humidity in your home.