BSRIA has recognised the well-documented notion that humidity plays an important role in assuring the well-being of building occupants.

In the UK, we spend over 80 percent of our time indoors, with approximately 90 percent of the associated costs of a building being staff related. Providing a good indoor environment is essential.

The recommended levels of humidity vary depending on the application, for example offices, data centres, or hospitals. In some industrial applications, such as heritage or storage, moisture stability is essential for preservation. In offices, the generally accepted levels of humidity may range between 40-60 percent.

As a standalone parameter, humidity is unlikely to cause thermal discomfort and levels outside the 40-60 percent range can easily be tolerated. A 10 percent increase in relative humidity is felt to be as warm as a 0.3°^C rise in the operative temperature. Human perception of dry air is generally due to contaminated or too warm air, rather than physical dryness, and air with high humidity is often perceived as odorous.

Blanca Beato-Arribas, asset performance team leader at BSRIA, commented: “Humidity extremes are undesirable and affect human comfort, productivity and health. Long periods of exposure to humidity levels under 35 percent should be avoided as they can cause eye irritation, throat and nose dryness. This is a common occurrence in aircraft, where humidity levels can be as low as 20 percent. Low humidity levels can also increase static electricity, which is a bigger cause of concern in data centres, where equipment can be damaged, or in places where there might be risk of gases igniting.

“At the other end of the spectrum, high levels of humidity encourage bacteriological and mould growth and increase the chemical and sensory emission from water borne building varnish and paint, contributing to poor indoor air quality.

“In summary, controlling the humidity levels and regular maintenance of the systems in an office building will avoid future costly problems related to mould growth, and also contribute to the well-being and productivity of the occupants.”