The Effect of Heating on Relative Humidity

Dry heated air in homes and other occupied areas has many damaging effects. It affects personal comfort and health. It also contributes to other problems. Separation of flooring,
interior trim, doors, and paneling are all costly results. Furniture pulls apart at glued joints. Pianos lose their tone quality. Plant growth is retarded. Books and paintings are vulnerable to dry rot.
It is this characteristic of heated air that makes proper relative humidity as important as heat-for comfort, health, and other elements. The damaging and costly results of dry, uncomfortable heat can be overcome. It is done by providing an artificial means to maintain proper indoor humidity. It simply requires installing one of the many types of humidifiers available. To select the most efficient type and size of humidifier for a given application, you must understand proper relative humidity.

Some levels of relative humidity may be ideal for health and comfort. But they may be less than ideal for other reasons. An indoor relative humidity of 60% may meet health and comfort needs, but it can also damage walls and furnishings. Fogging of windows is usually an indication that relative humidity in the building is too high. And this same condensation is taking place inside walls and other places that are vulnerable to moisture
damage. Therefore, we need to set safe limits of indoor relative humidity that give maximum benefits, but without damaging the structure itself. Table 35-2 shows
the proper temperature/humidity levels that will ensure these benefits.

Excerpt from Technical Institute Manual 2 from the Refrigeration Service Engineers Society. –

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