When you want to buy a fan, you think about which fan would be most suited to the space for which you are buying it. A fan is a budget-friendly way of cooling a home or a commercial space. You want to buy the best fan which will keep others comfortable while they go on about their life. While buying a fan, you have to consider different factors like the size, motor, and so on. One of the most vital factors is also the fan CFM. The CFM in fans is what contributes to the cooling factor they have.
How can CFM be defined? What does it stand for?
CFM is the unit in which airflow is measured. It is an acronym for Cubic Feet per Minute. The CFM tells us how much air a fan can move. This measurement indicates the volume of air in cubic feet that a fan can move in a minute. Different appliances like commercial fans, carburetors, air compressors, and bathroom fans measure the airflow in CFM. A higher CFM means the fan can move a higher volume of air.
If you are planning to buy an exhaust fan, you will see the CFM is the most essential factor which needs to be considered. An exhaust fan typically has a few hundred CFM. The fan in a cooker hood (kitchen hood) has a CFM of over 2000. And if it is a commercial kitchen exhaust hood, the CFM is over 5000. CFM is even used for HVAC systems.
What is CFM for kitchen fans?
A kitchen fan needs to have enough CFM for the area that you want to cool. A low CFM fan will not cool a room and will make the people in a room uncomfortable even if it is always running at the full speed. In fact, Cubic Feet per Minute or CFM is the determinant of a fan’s ability to move an amount of air in a room while running at its highest speed. Thus, CFM in fans is the most important measurement as it tells whether a fan can cool a particular room or not. Importantly, a bigger room needs a fan with a higher CFM.
Fans with a higher CFM have a more powerful motor and are more expensive. They might also use more electricity, making them more expensive to run.
Ceiling fan CFM and airflow
When buying a ceiling fan, you will find that the manufacturers have provided the airflow capacity in CFM, the electricity use in Watts, and the airflow efficiency in CFM per Watt. This information will help you to get an idea of a fan’s efficiency and airflow. Compare different fans and purchase the one which is best suited to your requirement.
A ceiling fan’s airflow tells you how much air it can deliver. This is of course measured in Cubic Feet per Minute or CFM. When the fan is running at its highest speed, the CFM is measured. And after that, it is divided by the watts used. The minimum CFM that a fan must have to function efficiently is 75 CFM/W. A fan with a higher CFM means it moves more air and is more efficient.
Factors impacting the fan CFM
Three important factors can affect the CFM for a fan. These are:
- RPM – This is an acronym for Rotations Per Minute. This shows the number of times a fan will rotate 360 degrees in a minute.
- Blade size – How much air a fan can move depends largely on the size of its blades. A fan with bigger blades will have a greater airflow. You will find fans with a wide range of blade sizes in the market. Usually, the popular fans have blade sizes in the range of 40″ – 65″.
- Blade Pitch – This refers to the angle tilt of a fan’s blades. The blade pitch is important in contributing to the fan’s airflow. A fan with a greater tilt can move more amount of air through a room. You will find it difficult to find fans with blade pitch lower than 13”.
Manufacturers work with these three elements to come up with the most efficient fan. With advanced software, they are able to simulate different designs to see what works best. This can explain why modern fans are a lot more efficient than older ones.
The layout of a room is also important. If you have a corner in a room, the cold air might not be able to access this part of the room. You might need a second fan for this or change the location of the fan. A rotating fan can help as well but this can affect the CFM.
Difference between Airflow CFM, Velocity & Airflow Efficiency
There are some other advanced measurements that allow you to see what fan will work for you. These are more advanced and are mainly used in commercial settings. These systems are more expensive and have to run as efficient as possible.
- Airflow CFM: This is the measurement of how much air a fan can move in cubic feet. CFM depends on the size of a fan. Airflow can also be measured in mph or miles per hour when calculating the speed of air movement. As we have mentioned earlier, an average fan has about 4000 CFM. The CFM of the most powerful fans is about 10,000.
- Air Velocity: While CFM is the measurement of the volume of air being moved, velocity is the measurement of its speed. It indicates how quickly the fan is moving the air.
- Airflow Efficiency: This is calculated by dividing the CFM by Watts. A fan with a high airflow efficiency means it uses energy efficiently, and it is as important as having a high CFM. But the choice of a fan should depend on the size of the room too. Cooling a bigger space would need more power. In that case, you should buy a fan with high CFM and average airflow velocity.
Amount of CFM you need
When shopping for a fan, the main things to consider are the CFM and airflow. You can use online CFM calculators to determine how much CFM you need. By now you are aware that a powerful fan has higher CFM. An average fan has a CFM of 4,000 – 5,000 when running at top speed.
The amount of CFM you need depends on the size of the room where you want to install the fan. For a room that is under 200 sq. feet, a CFM of 2000 – 3000 is enough. Whereas for a very large space exceeding 450 sq. feet, the ideal fan should have 5000 – 9000 CFM. Any standard bedroom or kitchen would need a fan of 3000 – 4000 CFM. And a bigger than usual living room or bedroom needs a 4000 – 6000 fan CFM.
|under 200 sq feet
|200-450 square feet
|more than 450 square feet
To conclude, we can state that CFM is a way to indicate how powerful a fan is. When you buy a new one, this is something that you should take into account as it greatly affects how much comfort you will get out of it.
The same principle applies to bathroom fans. If you notice that you have a lot of moisture after a shower or even mold, it might be time to replace your bathroom fan. A model with a higher CFM might be more suited for your bathroom.