Ceiling fans must be installed in all the required rooms for the building type as shown below in Table 30. In countries where ceiling fans are standard (such as India), the ceiling fans must be energy-efficient for this measure to be claimed.
Table 30: Minimum Required Spaces to be Provided with Ceiling Fans, by Building Type
|Building Type||Spaces that must have Ceiling Fans Installed|
|Homes||All habitable rooms (bedrooms and living rooms)|
|Offices||Office spaces (open and closed offices)|
Ceiling fans increase air movement, aiding human comfort by promoting the evaporation of perspiration (evaporative cooling).
The measure can be claimed if ceiling fans have been installed in all the required rooms for a project. For projects in India, ceiling fans must be awarded 4 or 5 stars by the Bureau of Energy Efficiency (BEE), or with an equivalent rating.
Ceiling fans are normally used to reduce cooling energy requirements by creating greater air movement in rooms. The increased air movement results in occupants feeling comfortable at a relatively higher temperature set point. In order to have this effect, the fan must be installed with the raised edge of the blade on the leading edge. The movement of the fan pulls the air towards the ceiling. In cooling mode, the effect is on perceived comfort, so if a room is unoccupied the fans should be switched off to avoid the waste of energy.
Ceiling fans can also be used to reduce heating requirements by reducing stratification of the warmer air that tends to rise to the ceiling. In this mode, the raised edge of the blades should be at the trailing edge. The movement of the fan pushes the warm air down towards the room. Fans often have a switch to change from cooling to heating mode, which works by reversing the direction of rotation of the fan motor.
In order to achieve the levels of air movement assumed by EDGE, Table 31 shows the minimum fan requirements for different room sizes. The first number in every case is the minimum required diameter in meters. This is also known as ‘total blade span,’ which is 2 times the radius as measured from the center of the fan to the tip of the blade. The second number is the optimum number of fans required in different sizes of rooms. For example, a 6m x 6m room would require a minimum of 4 fans with a minimum diameter of 0.9m or 900mm each.
Table 31: Minimum fan size (in meters)/Number of ceiling fans required for different room sizes
When considering fans larger than those provided in the table, consider the following rule of thumb. A fan that is twice the size will cover an area that is the square of the size factor. For example, a fan of 2m diameter could replace 4 fans of 1m diameter, and a fan of 3m diameter could replace 9 fans of 1m diameter.
However, the best way to determine the number of fans required is to compare the cfm (cubic feet per minute) of air that a fan is rated for. For example, if a standard small fan moves 60 cfm/watt, and the large fan moves 180 cfm per watt, you could replace 3 small fans with the larger fan. If the large fan moves 300 cfm per watt instead, you could replace 5 small fans with the larger fan. Please start with EDGE guidance to determine the number of small fans required, then include this simple calculation in your documentation to show the replacement calculation. Ideally, the cfm of ceiling fans should be sufficient to move the entire volume of the room in one hour. (Note that this is similar to air changes per hour for ventilation with a subtle difference; a fan moves air, not changes it.)
Relationship to Other Measures
The installation of ceiling fans to reduce cooling requirements improves occupant comfort without actively cooling the air. Ceiling fans are therefore only beneficial in spaces that have a demonstrable cooling load.
The installation of ceiling fans to reduce heating requirements does not necessarily decrease the heating load, but can improve occupant comfort by increasing the temperature at floor level and reducing the temperature gradient from floor to ceiling.
The base case assumes that no ceiling fans are specified. The improved case assumes that ceiling fans have been installed in line with the guidance above. The assumption is that the efficiency of the ceiling fans is 60W/fan (except in India where the efficiency assumed for the improved case is 40W/fan).
To verify compliance, the design team must demonstrate that ceiling fans will be or have been installed.
|Design Stage||Post-Construction Stage|
At the design stage, the following must be used to demonstrate compliance:
At the post-construction stage, the following must be used to demonstrate compliance:
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