Whole-home humidifiers typically use the fan-powered ductwork of furnaces to deliver humid air throughout a home. They are generally not integral to the furnace but function as an attached unit.
Furnaces and other heating systems do not humidify a home, and dry air commonly associated with cold weather can aggravate respiratory problems. By attaching a humidifier to a furnace, people can feel relief from symptoms.
Humid air also feels warmer than dry air at the same temperature. As a result, home occupants might feel comfortable at a lower temperature if a humidifier is added to their heating system, which can lead to significant savings during cold times.