Moisture and Humidity: The Negative Implications For Indoor Air
Sources of humidity
Signs of elevated humidity
How to reduce indoor moisture
Other Moisture-related Resources
Moisture can aggravate allergies and trigger asthma attacks. That is because allergy and asthma triggers like dust mites, fungi (or mold) and cockroaches all like moist, humid conditions in order to thrive.
Sources of Indoor Humidity
Many things can cause moisture to build up inside a home. The average household of 4 adds between 3 and 6 gallons of water to the air every day! There are several sources of moisture in the home. These sources include:
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People, plants, and pets: A person gives off three pints of moisture a day just by breathing.
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Cooking and dishwashing: These activities produce about one pint of water per meal.
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Showers: They release about ½ pint of moisture into the air.
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High humidity levels outside.
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Crawlspaces and basements: This is especially true if there is a dirt floor not covered by a moisture barrier. Moisture can seep through the soil into a home. Any water that leaks into crawlspaces or basements can raise moisture levels throughout the house.
Signs of Elevated Humidity
How To Reduce Indoor Moisture:
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Fix roof and plumbing leaks.
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Prevent seepage by correcting roof, gutter and drainage problems .
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Lay plastic over dirt in crawl spaces.
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Vent the clothes dryer to the outdoors and don't hang wet laundry indoors.
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Run the central climate-control system or a dehumidifier.
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Cover pots when cooking.
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Run a ventilation fan that exhausts to the outside when cooking. A circulating fan may remove some cooking odors from the air, but it will not remove moisture.
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Run a ventilation fan that exhausts to the outside for 15 minutes after bathing or until there is no condensation on the windows and mirrors.
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Buy a hygrometer to monitor interior humidity levels and maintain indoor humidity levels between 40 percent and 60 percent.
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If using a central humidification system, ensure that it is maintained and checked frequently. Over humidification can result in excessive moisture and mold
Other Resources
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Flannigan B, Morey PR. Control of moisture problems affecting biological indoor air quality: International Society of Indoor Air Quality and Climate, Ottawa, Canada, ISIAQ Guideline TF1-1996. 1996. www.isiaq.org
Updated May 17, 2002