When you run your air conditioner, the air indoors will be cooler than the outside air. The cooler indoor air and the hotter outdoor air will cause condensation to form on your windows. Eventually, pooling condensation can rot your window trim. At certain levels of humidity, you will have dust mite infestations. Dust mites are a health issue especially for people with allergies. High humidity indoors can also cause your paint and wallpaper to peel, your wood floors to cup and buckle, and your furniture to become mildewed. It can even affect the structure of your home, invisible to you until you need major repairs.

High indoor humidity creates an environment that fosters the growth of bacteria, viruses, fungi, mold and mildew, and wood destroying insects, which in turn can lead to structural damage and unhealthy indoor air quality. These microorganisms can create serious health problems for people and especially children due to their increased level of respiration. An increase in humidity also increases the concentration of VOCs. Volatile Organic Compounds are nearly omnipresent in our daily lives via the chemicals used to treat common household items. They exist in paints, carpeting, composite wood, upholstery, air fresheners, et cetera. When the relative humidity increases in temperature, these VOCs are released in higher amounts from these different sources. This means that a high humidity not only allows more VOCs in, but allows more chemical off-gassing to occur. The importance of avoiding high humidity levels in your home, to avoid structural damage and an unhealthy environment, is so great a free hygrometer/thermometer is included with every complete home inspection to allow you to monitor the indoor humidity levels at all times.