In what is perhaps a frustrating catch-22 for responsible homeowners, the better insulated and sealed against gaps and leaks your home is, the greater chance there is that you will experience a problem with indoor humidity. Humid indoor air can lead to issues with mold or mildew, paint damage, damp walls and wet spots on ceilings and floors. Wood furniture may become warped or damaged. Finding the right balance in humidity levels for your home's interior is based on the outdoor temperature.
Relative humidity, given as a percentage, measures how much moisture is present in the air compared to the maximum amount of moisture the air can hold at a particular temperature, or 100 percent. According to the University of Georgia, air is made up of both dry air and water vapor, and the temperature of the air determines how much moisture the air can hold. Warm air holds more moisture than cold.
General Humidity Recommendations
Recommendations for humidity levels at a given temperature are not usually exact, but are based on a range within which the inhabitants of a home are kept comfortable and the structure and items within the home are protected from damage. The University of Georgia suggests a temperature range of 68 to 72 degrees and a relative humidity of 25 to 50 percent as a broad guideline.
Suggested Humidity Levels
While you can use a tool called a sling psychrometer to take measurements to determine the relative humidity in your home, the Iowa State University extension service recommends a far simpler method to know when to take action: if condensation or frost appears on the inside of your window glass, you should act to reduce humidity. The service suggests you maintain an indoor relative humidity of 40 percent when temperatures remain above freezing outside, a relative humidity of 30 to 40 percent when temperatures fall between 20 and 32 degrees Fahrenheit and a relative humidity of 20 to 25 percent when temperatures fall below zero. The Indoor Air Quality website suggests maintaining an indoor temperature of 70 to 75 degrees, with similar guidelines for relative humidity levels and outdoor temperatures.
Reduce humidity levels by using a dehumidifier, running your air conditioner, improving ventilation or using less water inside your home. Dehumidifiers work by cooling the air, increasing its relative humidity to 100 percent, or the dew point. Water then condenses out of the air and is collected in a reservoir or directed into a drain leading from the device.