Indoor Humidity Levels: What to Know (2024)

By Amanda Lutz Updated February 6, 2024

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Indoor humidity measures the water vapor floating in the air throughout your home. It fluctuates based on the room, your activities, and the season. Humidity levels impact your everyday life by affecting your health, your sleep, and your home’s structural integrity. The U.S. Environmental Protection Agency agrees indoor relative humidity should be below 60% and between 30% and 50% ideally, but achieving this may be tricky. We’ll cover the signs of low and high indoor humidity, why these levels can be dangerous, and how to achieve an ideal indoor relative humidity.

Signs and Dangers of Low Indoor Humidity

Low indoor humidity means that your house’s humidity level is below 30%. Colder weather in the winter months can lead to a drop in humidity levels. Cold air carries less moisture. When it enters your home, your heating system warms it up and removes even more moisture. You may also have lower indoor humidity in the summer if you live in a drier climate and run your air conditioner often because air conditioners remove moisture from the air.

Some signs of low indoor humidity include the following:

If you’ve noticed any of the warning signs above, you may have low indoor humidity. You can check your home humidity levels with a hygrometer, which is an inexpensive device you can find at home improvement stores or online. Some newer thermostats list a room’s humidity level.

Viruses and bacteria thrive in lower humidity levels. If you suspect that low humidity is causing your cough or cold, you can use a humidifier or hot showers to add more moisture to the air. Low humidity can shrink wood and damage windowpanes, floors, and furniture, compromising your home’s structural integrity.

Signs and Dangers of High Indoor Humidity

High indoor humidity is anything higher than 60%. Humidity levels spike in the summer because warm air holds more water vapor. Summer heat can cause high humidity levels in your home, but reduced ventilation, leaks, poor insulation, and everyday activities—such as cooking and showering—can also generate excess moisture.

The signs of high indoor humidity may include:

You may be more susceptible to hay fever and allergies because dust mites thrive in high humidity. Excess humidity for an extended period could cause mold growth, which can lead to health concerns such as sneezing, a runny nose, skin rashes, and red, itchy eyes. Long-term mold exposure can result in persistent headaches, confusion, insomnia, and severe respiratory conditions. 

If you’ve been exposed to mold, you can clean it while wearing a mask and fix any moisture problems so that the mold doesn’t return. You can also contact a restoration company to clean up the mold if the problem is extensive.

What Is the Ideal Indoor Humidity?

Ideal indoor humidity depends on a number of factors, including whether you have a condition such as asthma and what month it is. The following table shows the ideal level of humidity to achieve in your home based on specific circumstances.

CircumstancesIdeal Indoor Humidity Level
Bacteria growth prevention40%–60%
Dust mite prevention35%–50%
Winter months30%–40%
Summer months40%–50%
Respiratory condition30%–50%

How to Achieve Ideal Indoor Humidity

Achieving ideal indoor humidity levels will benefit your health and sleep while maintaining your home’s structural integrity. You can take several steps to increase or decrease your home’s humidity levels, but you need to determine how dry or damp your indoor air is first.

Hygrometers and modern thermostats both measure the air’s water vapor, but if you don’t have either, you can quickly test your humidity level by taking the following steps: 

  1. Pour a glass of water.
  2. Add two or three ice cubes. 
  3. Place the water in a room away from the kitchen and bathrooms.
  4. Return to the glass in four minutes.

This method won’t provide you with an accurate moisture reading, but it will help you determine whether you’ll need to investigate the situation further. If condensation forms on the outside of the glass, it could mean you have too much moisture in your home. If you don’t find any condensation on the glass, the air may be too dry. You can make an educated guess based on these results and by making note of possible signs of low or high humidity in your home.

If you have low indoor humidity levels, you can increase air moisture levels in a few ways, including the following: 

If you have high indoor humidity levels, you can dry the air using the following methods:

Our Recommendation

Maintaining ideal indoor humidity levels in your home will help you sleep, keep you healthy, and preserve your home’s structural integrity. Test your home’s moisture levels or look for signs that indicate high or low humidity.

When a home’s humidity level is too low, the air will be drier, and you could develop colds or respiratory complications. We recommend using a humidifier to increase the amount of water in the air and ensuring your home doesn’t have any air leaks by sealing windows and doors.

When a home’s humidity level is too high, you may see mildew and mold growth. We recommend you purchase a dehumidifier and use your AC unit to remove high levels of moisture in the air.

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Indoor Humidity FAQ

What are the signs of high humidity in the home?

The signs of high humidity in the home include a musty smell, condensation on your windows, mold growth, and peeling paint. You may also notice rotting wood or a warped wooden floor.

What is a sign of low humidity in a house?

A sign of low humidity in a house is dry, itchy skin. Homeowners may have other symptoms, such as feeling cold all the time, having difficulty breathing, and being dehydrated.

What is the difference between air conditioning and a dehumidifier?

The difference between air conditioning and a dehumidifier is that air conditioners take hot air from your home, cool it, and blow it back out, while dehumidifiers remove moisture from the air.

What are the most common causes of high humidity in a home?

The most common causes of high humidity in a home are poor ventilation and malfunctioning HVAC systems. Wet areas, such as bathrooms, require adequate aeration to avoid moisture buildup. Exhaust fans, dehumidifiers, and an operational air conditioner will help eliminate the issue.

Do fans reduce humidity?

Yes, fans reduce humidity by reducing excessive moisture. A ceiling fan’s breeze makes water evaporate, and exhaust fans remove humidity from damp rooms.