Ceiling fans are one of the more credible techniques to decrease the energy consumption for air conditioning and improve comfort. Historically, ceiling fans have first emerged in hot humid climates and have become more and more popular in certain parts of the world from the early decades of the last century.
Ceiling fans when in use can extend the summer comfort zone, i.e. improving the thermal comfort at higher temperatures (e.g. up to 29 °C). As such, they can have several substantial advantages:
1. In non-air conditioned buildings, ceiling fans can substantially extent the periods of acceptable thermal comfort conditions resulting in better thermal comfort and improved productivity;
2. in air conditioned buildings, they can reduce the use of air conditioning (in hours of operation and in energy use) by setting the room thermostat at a higher temperature.
3. Ceiling fans can avoid the need to install active cooling systems
Ceiling fans can also improve the energy efficiency during the heating season by reducing vertical stratification: the warm air in the top of the rooms is then driven to the bottom parts of the room. This typically requires to change the sense of rotation of the blades.
Studies, mainly performed in USA, have shown that there are in air conditioned buildings important energy gains associated with the use of ceiling fans. However, monitoring of a high number of buildings has shown that energy gains are only possible if associated with an increase of the set point temperature.
The present paper aims to present the main advantages of ceiling fans, the existing knowledge on the impact of ceiling fans on comfort as well as the knowledge on the expected energy gains. Finally, some recommendations on the proper use of the fans are given