Cause of Condensation on Interior House Walls

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Condensation may lead to mold growth.

The most common cause of condensation on your walls is excess moisture inside your home. Some condensation is harmless, even normal. But excess condensation can lead to a host of problems. Fortunately, you can get rid of excess condensation on your walls and control excess moisture in your home.


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Warm air holds more moisture than cold air. Thus, when warm air comes in contact with a cold surface, the air quickly cools and the excess moisture releases in the form of condensation. You'll see this commonly on windows, which are generally the coolest surface in an insulated home. However, condensation can also form on walls.


Some condensation is normal and harmless. Excess condensation, however, can lead to serious problems. For example, excess condensation can result in musty odors, peeling or blistering paint, rotting wood, and mold and mildew growth. Among these, mold and mildew growth is potentially the most dangerous. Mold and mildew growth can cause serious health problems, including skin and eye irritations and respiratory problems. Pregnant women and people who already have respiratory conditions are particularly susceptible to these problems.



Remove excess condensation from the walls using a dry towel. You can also run a dehumidifier to quickly remove excess moisture from the air. The United States Environmental Protection Agency recommends keeping the relative humidity in your home below 50 percent. You can purchase a hygrometer at your local hardware store to measure the relative humidity in your home.


In addition to running a dehumidifier, you can control the excess moisture that leads to condensation by opening windows, assuming it is not humid outside, for a few minutes per day; running an exhaust fan in high moisture areas, such as bathrooms and kitchens; and reducing moisture-generating activities, such as cooking, showering and laundry. Additionally, consider installing vapor barriers should you be building new or willing to weather renovation. Vapor barriers go on the warm side of the wall, generally between the framing and the interior sheathing or wall finish, and should have a permeability rating of 0.25 or less.