Relative Humidity

Relative humidity is a measure of the amount of moisture in the air in comparison to the total amount of moisture that the air can hold for that particular temperature. It is express as a percent. Humidity is the invisible water vapor in the air.

The warmer the temperature, the more capacity the air has to hold moisture. The cooler the temperature, the less moisture the air can hold. For example, a reading of relative humidity of 80% at 75 degrees means that the air can only hold 20% more moisture before 100% saturation occurs. A reading of 80% at 60 degrees also means that the air can hold only 20% more. The difference is that the air can hold more moisture at 75 degrees than 60 degrees. Thus, even though R.H. reads the same at 80%, there is more moisture in the air at 75 degrees than 60 degrees. This is because there is more capacity of the air to hold more moisture.

Condensation

When the air no longer has the capacity to hold more moisture, it is said to be 100% saturated. This is when condensation occurs. Condensation can occur in your home in the form of sweaty pipes. Condensation can also occur on the mirror in your bathroom when a hot shower steams up the mirror. Warm air expands giving it more of a capacity to hold moisture. As the warm air comes into contact with a cold mirror, a cold window, a cold glass of water, or a cold pipe, the air becomes cooler. The temperatures on these surfaces are below the dew point of the air holding the moisture. The amount of moisture in the air has not changed. The change that occurs is that the cooler air has a reduced capacity to hold the moisture. The air becomes 100% saturated and water droplets become visible which is called condensation.

Optimum Levels

The optimum level is between 30 to 50%.

Problems can begin to occur when relative humidity is over 50%. High humidity is not good for our homes and will begin to damage the integrity of our home. At these higher levels, biological growth will flourish. Mold spores will start growing into a colony and dust mite reproduction will increase. In fact at 70%, dust mites can live comfortably without the moisture that our bodies give off. Higher humidity and condensation promotes mildew, bacteria, mold, and insect growth. Higher humidity promotes corrosion and decay.

Problems also occur when R.H. is below 30%. Wood in the homes looses its moisture and begins to shrink. If the wood surface is painted, the paint begins to crack and chip. Your hardwood floors will also begin to shrink. Low humidity is what causes static electricity. It can be very uncomfortable to live in a home where you get 'shocked' when you touch something or someone. Too dry of air can also dry out the inside or your nose and dry out your lips which can also lead to discomfort.

Hygrometer

Relative humidity at 45% is a comfortable level for humans. A tool that can measure relative humidity is called a hygrometer. This can be an important tool to have if you have humidity problems. This tool is especially important to use for those who have allergies. Knowing the humidity levels and keeping control over high humidity will reduce the allergens produced by mold and dust mites.

Controlling Humidity

Controlling humidity is not hard to do if you know what to look for. Using a hygrometer will let you know where your level is at. Below is a short list of what you can do and what you can be aware of when it comes to controlling relative humidity.

• Take shorter showers.
• Don't take such hot showers and bathes that the steam fogs up your bathroom mirror.
• Leave the exhaust fan on for 10 minutes after taking a shower. Make sure it is vented to the outside.
• Use the exhaust fan while you cook. (Boiling water adds a lot of moisture to the air.) Also make sure that the kitchen exhaust fan is vented to the outside.
• Don't over water your plants.
• Make sure that the dryer is vented to the outside.
• Don't leave wet clothes or towels lie on the floor. Hang them up so they can dry out.
• Use a dehumidifier if humidity levels are too high.
• Use the air conditioner if humidity levels are too high. By reducing the temperature, the air will not be able to hold as much moisture.
• Have good ventilation throughout the house.
• Remove aquariums if moisture is a problem as they add to the moisture content of the air.
• Use a humidifier if the air is too dry.
• Look for condensation and leaks and mold growth.
• Use a Hygrometer to monitor the relative humidity levels.

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