What Is Humidity?
Humidity refers to the amount of moisture or water vapor in the air. Relative humidity (RH) is a percentage that indicates the amount of moisture in the air relative to the maximum amount the air can hold at a given temperature. For example, if the air contains half as much moisture as it possibly can, it is said to be at "50 percent relative humidity." According to the EPA, the ideal relative indoor humidity level is 30 to 50 percent.
How Does It Affect the Home?
When the humidity level rises above 50 percent, condensation -- excess moisture falling out of the air and onto cold surfaces -- develops on pipes, windows, and tile, providing an ideal environment for mold, mildew, and rust. When mold and mildew are present in closets, clothes and linens can absorb a musty odor. Excessive humidity can also warp wood, causing damage to floors and furniture. Too much moisture can even cause labels to slip off of bottles -- the reason medications should not be stored in a humid bathroom.
How to Measure Humidity
To measure the humidity level in your home, it is best to purchase a hygrometer or humidistat, both of which are available at home centers and hardware stores.
Tips for Dehumidifying Your Home in Summer
To keep humidity levels down, run air conditioners and fans together.
Operate exhaust fans in kitchens and bathrooms, and vent clothes dryers to the outdoors, if possible.
Turn off lights and other heat-generating appliances when not in use.
Allow fresh air in when it is cool outside -- preferably in the morning and at night -- and keep it circulating with fans.
If condensation forms on metal windows, seal windows tightly, add weather stripping, and install storm windows.
Repair leaky faucets and pipes. As a temporary measure, wrap them in pipe insulation to keep them from dripping.
Remove absorbent materials -- rugs, carpets, and pillows -- from areas subject to chronic moisture problems, such as bathrooms, basements, and laundry rooms.
In basements, an electronic dehumidifying unit may prove helpful: Removing the extra moisture will help control mustiness and odors. But because dehumifiers emit heat, they're not recommended as a solution to whole-house humidity problems. If you do purchase a dehumifier, choose one with an Association of Home Appliance Manufacturers seal of approval.
How to Deal with a Humid Closet
Humidity in closets and storage spaces can produce a musty odor. To control moisture, place desiccants in closets, cabinets, drawers, and storage boxes to control moisture. They are available from stores selling closet-organizing products and housewares. These nonmechanical dehumifiers are made from several different materials:
Silica gel -- a nontoxic, non-corrosive form of silicon
Molecular sieve -- a combination of desiccant materials such as zeolite aluminosilicates
Activated clay -- a naturally occurring, nonhazardous, sulfur-free substance
Make Your Own Desiccant
DIY desiccant! Use chalk to keep humidity from storage spaces. Fasten a rubber band around a dozen pieces of chalk and cover the band with a ribbon, allowing enough loop to hang over like a hook.
For piano owners: Extreme fluctuations in relative humidity are harmful, since they can affect both tone and pitch. In the summer, moist air can cause the soundboard to expand, causing the piano to go sharp. Moisture can also cause the strings to rust. It is best to closely monitor humidity near a piano, and use a portable humidifier to manage relative humidity.
In particularly hot, humid weather, you may need to store breads in the fridge, which will retard mold growth for 2 to 3 days.
For wine-lovers: Whether you own many bottles, or just several, storing your wine properly will ensure that it always tastes its best. The ideal relative humidity is between 60 and 75 percent -- a bit higher than the recommended levels. Choose a storage space that's out a direct sunlight, and control for humidity.