How Humid Should I Keep My House?

Updated February 21, 2017

Too much or too little humidity can make your indoor environment uncomfortable. More worrisome, however, is that too much or too little humidity can cause damage to your home and your health. Fortunately, there are ways to keep the humidity in your home at appropriate levels.

What is Humidity?

Humidity refers to the amount of water vapour in the air. Humidity is generally measured in terms of relative humidity (RH). The RH is determine by taking the actual vapour density, dividing by the saturation vapour density and multiplying that number by 100. Most people prefer to measure the relative humidity by purchasing a hygrometer. A hygrometer, which comes with most humidifiers, will read the relative humidity in your home and display it automatically.

Ideal Humidity

The American Society of Heating and Air Conditioning Engineers recommends maximum indoor relative humidity percentages that are supported by the U.S. Environmental Protection Agency. For example, for outdoor temperatures below minus 20 degrees Fahrenheit, the relative humidity should not exceed 15 per cent. For outdoor temperatures between minus 20 and minus -12.2 degrees C, the relative humidity should not exceed 20 per cent. The EPA stresses that at no temperature should the relative humidity indoors exceed 60 per cent.

Humidity Problems

The reason there is an ideal relative humidity in the first place is that too little or too much humidity can cause a host of problems. Too little humidity can cause damage to furniture, chapped skin, sore throat and breathing problems. Too much humidity can cause condensation formation on windows, mould and mildew growth, musty odours, allergic reactions and significant breathing problems, especially for pregnant woman and people who already have respiratory problems.

Humidity Control

If there is too little humidity in your home, consider running a humidifier. More than likely, however, the problem will be that there is too much humidity in your home. To remedy this, consider running a dehumidifier in the winter months with a built-in hygrometer. That way, you can set the dehumidifier to keep the relative humidity at a certain percentage. In the summer months, consider running an air conditioner, which will help remove moisture from the air. Additionally, lower humidity by running an exhaust fan, installing vapour barriers and cutting down on moisture-generating activities, such as long showers, cooking and doing laundry.

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About the Author

Thomas King is a graduate of the University of Pittsburgh School of Law where he served as managing editor of the "Pittsburgh Journal of Environmental and Public Health Law." He currently lives in Aberdeen, Washington where he writes and practices law.