Heating and cooling systems are designed to provide a comfortable indoor environment of 65 to 70 degrees and 30 to 50 percent relative humidity. The temperature is straightforward; just move the thermostat up or down. The humidity is more complicated, particularly with dry winter air.
When the temperature drops below freezing outside and your thermostat reads 70, relative humidity indoors can sink below 10 percent. For people, that’s dry enough to chafe skin and trigger coughing. For houses, that’s dry enough to open trim joints and produce potent shocks from static electricity. The solution: add moisture.