I would venture to say I study humidity more than any issue in our field. I have read numerous articles, measured homes, done before and after, talked with field representatives, and of course listened to my home owners, to come to my conclusions. Many of the numbers I cite do come from studies on humidity and its affect on pathogens such as the influenza virus. During the winter months the Charlotte metro region air tends to be very dry inside our homes this is based on the low outdoor temperatures. Factors that contribute to a home that has low humidity are age, insulation, tightness of structure, and natural air changes per hour (doors and windows opening and closing). I suggest that you invest in a hygrometer from Radio Shack or from Amazon; this will give you a point of reference. Ideally the humidity in your home should be about 40%-50% in the winter months, if it is in the 20% range that is unacceptable and will lead to health problems. Humidity in the winter can help stop the transmission of the influenza viruses, the higher the humidity, above 45% the less chance of the pathogen staying air borne and the pathogens survivability decreases. Another benefit to higher humidity in the winter is the insulating effect moisture has on the body; the thermostat can be set at a lower level because humidity makes us feel warmer. NASCAIR installs humidifiers based on the need, the tighter the home the less humidity it should need the older the home the more humidity it will need. NASCAIR installs Honeywell and Aprilaire steam and by-pass humidifiers, one size does not fit all and the house needs to be assessed for the application, typically these humidifiers add 12 -23 gallons a day. Again check your humidity to see if it is an issue. You can expect to pay above $2000.00 for a professionally installed steam humidifier; they are considered an appliance and get a dedicated circuit. Call NASCAIR for an appointment to check the health of your home. 803-802-8884.
Please note, cool mist humidifiers are not recommended.
Suggested reading: WebMd health and humidity, Mayo Clinic health and humidity
Cited articles: www.plosbiology.org