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Buffering Humidity with Interior Finishes

The relative humidity of indoor air often fluctuates. Interior finishes can help moderate those changes, improving comfort and IAQ as well as saving energy.

One study of an average 1500 ft2 home found that the drywall alone on walls and ceilings had the ability to store about 17 pounds of water, while special moisture-storage coatings on all walls and ceilings yielded nearly 60 pounds of water storage. These capacities can easily be enough to move daytime interior relative humidity from an uncomfortable 60% range to an acceptable 40% range. The moisture-storage capacity of earthen plasters can make them excellent humidity buffers as well, with some research showing the ability of clay finishes to accomplish daily cycling between 75% and 33% indoor relative humidity.

Do we really want to introduce pounds and pounds of moisture into our building enclosures, though? Could we be flirting with mold problems?

Published December 2, 2013