Ceiling fan
A ceiling fan is a mechanical fan mounted on the ceiling of a room or space, usually electrically powered, suspended from the ceiling of a room, that uses hub-mounted rotating blades to circulate air. Ceiling fans typically rotate more slowly than other types of circulating fans, such as electric desk fans. They cool people effectively by introducing slow movement into the otherwise still, hot air of a room. Fans never actually cool air, unlike air-conditioning equipment, they in fact heat the air due to the waste heat from the motor and friction, but use significantly less power (cooling air is thermodynamically expensive). Conversely, a ceiling fan can also be used to reduce the stratification of warm air in a room by forcing it down to affect both occupants' sensations and thermostat readings, thereby improving climate control energy efficiency.
Energy conservation in the United States
As furnace efficiency gets higher, appropriate matching of equipment size to distribution system capacity and building load becomes more critical to optimizing equipment ability to maximize efficient operation. Installing much lower output high-efficiency replacement equipment offers opportunity for comfort and savings gains, but improving the building envelope through air sealing and adding more insulation, advanced windows, etc., should be explored concurrently or before replacement equipment design stage. The passive house approach produces superinsulated buildings that approach zero net energy consumption. Improving the building envelope can also be cheaper than replacing a furnace or air conditioner.