CFM Calculation and Air Changes Calculation


CFM Calculation

CFM of a room helps you to choose the right fan or any other HVAC system for your room in order to keep a comfortable temperature inside your home. The term “CFM” is the acronym for “cubic feet per minute”. It is used to describe the efficiency of a fan in terms of airflow. CFM air flow calculation is a mathematical process used to determine the cubic area of a room and the required rate of air circulation through the room. Every fan has a CFM rating, so if you know the CFM of your room it will be easier to choose a suitable fan.

For CFM calculation of a room, you’ll require a Measuring Tape. First of all, measure the width, length, and height of the room. Multiply the three quantities to find the volume of the room. Let’s suppose, a room has a width of 6 feet, length of 8 feet, and a height of 10 feet. Multiply 6 times 8 times 10 to get 480 cubic feet of volume.

Now, multiply the volume by the number of times that you want the air to exchange or ventilate in an hour. Let’s say you want the air to be exchanged twice during one hour. Multiply 480 times 2 to get 960. Now divide this quantity by 60, since there are 60 minutes in one hour, to get CFM. In the above example, dividing 960 by 60 gets you a CFM of 16.

The formula for CFM calculation can be written as:

Air Changes Calculation

If you want to calculate the air changes of a room, then you will have to proceed by the reverse process. Air change is basically the number of times air enters and exits a room during an hour from a HVAC system. It is a great deal of a challenge to balance the airflow of a HVAC system. Most calculations don’t take in account the required ventilation and only use the heat gain and loss of a room while determining airflow. Air change calculations will simply the task of air balancing.

After determining the air change, one can compare it to the standard table of Required Air Changes for a room. If your calculations lie in the range, then you can proceed with the designing and balancing of the airflow of your system.

To calculate the air change per hour, multiply CFM of the airflow supply times 60 minutes and divide by the volume of room in cubic feet.  The formula can be written as:

The CFM calculation and air change calculation are complementary to each other- CFM depends upon air change and vice versa. It is very important for a room to have an HVAC system installed according to the CFM to keep the required temperature. For more update about technology stay tune with engineerspro.