Relative Humidity vs Absolute Humidity: Understanding the Differences and Their Impact on IAQ
If you’ve ever traveled from Colorado to Florida in the summer, you understand how humidity impacts the environment. Stepping off the plane in Florida, you feel hotter and stickier. If you’re not used to humidity, it feels like you could drink the air. On the flip side, going to Colorado, you’re plagued by dry skin and notice yourself shocking light switches when you touch them. Indoor humidity levels also impact indoor air quality within your building, but not all humidity is the same. Learn to distinguish between relative humidity versus absolute humidity and what it means for your building’s air.
What Is Relative Humidity?
Relative humidity refers to the percentage of water vapor in the air relative to its temperature. It is the actual amount of water vapor relevant to how much water vapor air can hold at a certain temperature. Since warmer air holds more water vapor than cooler air, maximum humidity levels will differ based on temperature.
What Is Absolute Humidity?
Absolute humidity refers to the amount of water vapor regardless of the temperature. You calculate absolute humidity by dividing the mass of water vapor by the mass of dry air.
Key Differences Between Relative and Absolute Humidity
Now that you’ve got an overview of absolute humidity versus relative humidity, you can dig deeper into how they differ.
Measurement Units and Formulas
You measure absolute humidity as grams of water vapor per cubic meter of air. Relative humidity is calculated as a percentage of the amount of water vapor you would need to saturate the air at the same temperature.
To measure relative humidity, you need to calculate the saturation point, divide the actual vapor pressure by the saturation vapor pressure, and multiply the result by 100.
Temperature Dependency
Although the absolute humidity level will be different based on the air temperature, you don’t need to know the temperature to measure it. Absolute humidity only measures the volume of water vapor in a specific amount of dry air.
For example, you can measure the absolute humidity at 50°F and 85°F and end up with a reading of 10g/m3. Although the relative humidity would differ at these temperatures, the amount of water vapor in the air would remain the same.
Real-World Examples
You can feel relative humidity by comparing temperature shifts in different locations. As you travel from Colorado to Florida, you will notice that 80°F feels different in both locations. Because Colorado is less humid, 80°F feels cooler, while Florida’s high relative humidity makes 80°F uncomfortable.
You can measure absolute humidity to control excess moisture levels in environments to ensure comfort, optimize equipment performance, and guard against the spread of airborne particles. In manufacturing, you might test it to monitor food quality and consistency. Higher absolute humidity makes food more susceptible to mold and spoilage, while lower absolute humidity can dehydrate food or make it lose texture.
Importance of Humidity in Indoor Air Quality (IAQ)
Like it does outdoors, indoor humidity levels also impact the air quality inside your building.
Effects of High Humidity on Health
High humidity makes it harder to cool off, so you can become dehydrated by sweating more. It can also make you lose electrolytes, which can cause muscle cramps. It can also affect asthma, heart disease, diabetes, and other illnesses.
Effects of Low Humidity on Health
Air that is too dry can also worsen lung conditions, including asthma and bronchitis. It can give you a sore throat and make it harder to swallow. Low humidity in the air causes nosebleeds, dry skin, and in some cases, it worsens your stress levels. A building with cold, dry air often uses heaters, which increase your risk of getting colds and the flu, which is more common during winter months.
Role of Humidity in Mold and Pollutant Growth
For the health of your tenants, it’s critical to avoid mold growth in damp environments. As it grows, mold releases spores into the air and spreads to other surfaces within your building. If your building is too humid, you’re more likely to develop a mold growth or mildew problem, which can make your tenants sick. Higher indoor humidity levels can also increase pollutants in the air, such as dust mites and allergens.
Track Humidity With Attune’s IAQ Monitoring Solution
Whether you’re trying to keep office workers comfortable and productive or preserving valuable pieces of art, you need the right humidity level in your building, which means you need a reliable tool for tracking IAQ. Attune’s IAQ solution helps you visualize airborne contaminant levels in real-time so you can continually monitor safety and comfort and ensure you have the data needed for reducing humidity in your office, data center, healthcare facility, or other commercial indoor environment.
Our plug-and-play sensors let you customize the right solution for your needs and monitor relative humidity, volatile organic compounds, and more. See fluctuations in your building’s relative humidity and alert yourself to potential ventilation issues before they become a problem. Schedule a demo today to learn more.
Frequently Asked Questions
What Is the Difference Between Relative Humidity and Absolute Humidity?
Absolute humidity measures the volume of water vapor in a specific unit of air. Relative humidity measures the percentage of water vapor in the air relative to the temperature. The maximum humidity differs based on temperature, and you measure relative humidity based on the highest saturation level at any given temperature.
How Does Relative Humidity Affect Air Quality?
Higher humidity impacts air’s ability to circulate. When your air becomes too humid, pollutants, mold, and other particles are trapped in the air, making it easier for people to get sick. High humidity also makes it harder for the body to cool down, causing people to sweat more. It can lead to dehydration and respiratory issues.
If your air is humid, your air conditioner may be working overtime to keep people cool, which bumps up energy costs.
Why Is it Necessary To Learn About Absolute and Relative Humidity?
Relative humidity impacts how comfortable we feel in a building. If you’re using sensors that also monitor absolute humidity, it’s important to understand the difference so you can maintain optimal air quality.
Absolute humidity also helps you understand water vapor levels in your building. Water vapor can enter your building through cracks in walls and the foundation. High water vapor levels in your building can also signal a potential mold problem. Knowing why each of these data elements is important will help you read your building reports and understand what the data is telling you so you can create a comfortable, clean, and safe working or living space for your tenants.
