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What is CFM and How Much CFM do I need?

CFM stands for Cubic Feet per Minute, and is a measurement used to quantify the volume of air that a ventilation system can move within one minute. Essentially, it indicates how much air is being pushed or pulled by the fan or blower.

In practical terms, CFM tells you how quickly air is being exchanged or moved by a ventilation system. CFM is an important metric when selecting ventilation equipment because it helps ensure that the system can adequately remove smoke, heat, moisture, and other airborne contaminants from a space. The CFM rating needed depends on various factors, including the size of the room or space, the type of activity producing contaminants, and any specific ventilation requirements for safety or comfort.

BTU is also an important factor when choosing CFM. BTU stands for British Thermal Unit. It is a unit of measurement for energy, commonly used in the context of heating and cooling systems, as well as in the measurement of energy content in fuels. One BTU is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit at sea level. To calculate the required Cubic Feet per Minute (CFM) of airflow for a kitchen range hood based on the British Thermal Units (BTU) of your stove, you can use a general rule of thumb. This calculation helps ensure that your range hood has sufficient ventilation to handle the heat output of your stove. With both CFM & BTU considered, here's a step-by-step approach to help you determine the amount of CFM you need for your range hood:

Step-by-Step Calculation

Step-by-Step Calculation

Determine the Total BTU Output:

  • Add up the BTU ratings of all the burners on your stove. For example, if your stove has four burners with BTU ratings of 15,000, 12,000, 10,000, and 9,000, the total BTU output is: 15,000+12,000+10,000+9,000=46,000

Apply the General Rule of Thumb

  • You need 100 CFM for every 10,000 BTU of your stove's output

Calculate the Required CFM:

  • Using the example above: 46,000 BTU / 100=460 CFM

Example Calculation

Here is a simple calculation applicable for a typical 24" deep Gas Cooktops.

For average cooking, you will need 1.2 CFM per square inch.

30" Wide Cooktop

24D x 30W=720 sq inch ÷ 1.2 =  600 CFM - Min. 6” Duct (8 " Duct Recommended) 

36" Wide Cooktop

24D x 36W = 864 sq inches ÷ 1.2 = 720 CFM - Min. 8” Duct (10" Duct Recommended) 

42” Wide Cooktop

24D x 42W = 1008 sq inches ÷ 1.2= 840 CFM - Min. 8” Duct (10" Duct Recommended) 

48" Wide Cooktop

24D x 48W = 1152 sq inches ÷ 1.2 = 960 CFM - Min. 8” Duct  (10" Duct Recommended) 

54" Wide Cooktop

24D x 48W = 1296 sq inches ÷ 1.2 = 1080 CFM - Min. 10” Duct 

60" Wide Cooktop

24D x 60W = 1440 sq inches ÷ 1.2 = 1200 CFM - Min. 2 x 8" Duct (2 x 10" Ducts Recommended)

Please note: If your stove is deeper, you’ll need to recalculate. For heavy cooking or BBQ use, multiply this number by 1.5 for optimal results

Steps to Determine How Much CFM you Need

  • Determine the Size of the Cooking Area: Measure the length, width, and height of the cooking area or stove where the range hood will be installed. This will give you the volume of the area in cubic feet (ft³).

  • Consider the Type of Cooking: Different cooking methods produce varying amounts of heat, smoke, steam, and airborne contaminants. For example, heavy-duty cooking such as frying or grilling generates more pollutants than light cooking such as boiling or steaming.

  • Refer to Guidelines or Standards: Some building codes, ventilation standards, or appliance manufacturer recommendations provide guidelines for the minimum CFM rating for range hoods based on factors like the size of the cooking area and the type of cooking equipment.

  • Calculate your BTU's: Using the BTU calculation method in this guide, calculate the BTU output of your range. You do not need the exact CFM based on your BTU calculation but you should try and match it as closely as possible, especially for gas ranges since they typically produce more heat.

  • Consider Additional Factors: In addition to the cooking area size and type of cooking, other factors such as kitchen layout, ceiling height, duct length and configuration, and the presence of make-up air systems may influence the required CFM.
built-in insert range hoods by victory range hoods

Selecting a Range Hood

Choose a range hood model with a CFM rating that meets or exceeds the calculated requirement. Consider factors such as hood design, noise levels, energy efficiency, and any additional features or requirements. By following these steps and considering your specific cooking habits and kitchen layout, you can select a range hood that provides effective ventilation and enhances the comfort and functionality of your kitchen.

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