Traditional Furnaces A furnace draws air from the house into a ductwork system, taking it to an area where it is warmed before being delivered back to living spaces. Furnaces use blowers to recirculate the warmed air. Circulating air is drawn through a filter that helps rid the house of dust and other particles. Gas and oil furnaces have a pilot light that warms a heat exchange unit, which in turn warms the air before it is circulated back through the house. These furnaces have a flue where exhaust gases vent to the outside. An electric furnace uses heating strips, or elements, to warm the air. The home's temperature is controlled by changing the settings on a thermostat, usually positioned on a wall at eye-level. The thermostat shows the current temperature of the room.
Electric Heat Pump Heat pumps work by shuffling heat from one place to another. Heat pumps extract warmth from outdoor air, from ground or surface water, or from the earth. The air is warmed more by the system if necessary, then circulated through the house. They also serve as air conditioners during warm weather.
Space Heaters You might see portable space heaters that are electric or fueled by gas or kerosene. These should not be used to qualify an area as heated living space. Gas space heaters are common in some areas. They may be freestanding or may be attached to a wall. If permanently attached, they do allow an area to be counted as heated living space (provided other qualifications are met).