How to Calculate CFM for Range Hoods – All You Should Know

How to Calculate CFM for Range Hoods

CFM or cubic feet per minute describes the volumetric flow of a substance. How to calculate CFM for range hoods is a commonly asked question. For starters, it is important to note all calculations are based on the HVI (Home Ventilation Institute) recommendations and building codes in your region.

The kitchen range hoods are a great way of removing moisture, heat, odor, and smoke in your kitchen as you cook. CFM measurements rate the effectiveness of the range hood. How do you determine the best CFM for your range hood? After all, everyone wants to invest in a range hood that is effective and moves enough air. Read on!

  • Calculate CFM for Range Hoods
  • Understanding the Variables
  • How to Determine Your Range Hood CFM
  • 1.Get your kitchen measurements
  • 2.Determine the BTU units your cooker produces
  • 3.The duct length of stale air the range hood needs to overcome

How to Calculate CFM for Range Hoods

Understanding the Variables
For starters, there are no set industry standards that determine the required CFM range required for the different ranges and stoves. There are many variables in every installation that makes it difficult such as the distance between the cooking surface and the hood, and the air current flow in the kitchen.

Other variables include the types and amount of food cooked. For instance, are you steaming fish or vegetables? Cooking with strong smelling spices might cause the house to acquire a certain smell too. Also, indoor grilling produces a lot of smoke affects the CFM score.

How to Determine Your Range Hood CFM
Here are three easy steps on how to calculate the CFM of your range hood. The three major aspects to consider include:

  • Your kitchen measurements
  • The British Thermal units the range hood produces
  • The British Thermal units the range hood produces
  • Ducting between the hood and outside
  • According to the HVI building code, the kitchen should have a 15 ACH or air change per hour.


    Get Your Kitchen Measurements
    Measure the kitchen’s length length, width, and height of the kitchen that the range will serve. The next step is calculating the volume of air in the room.
    For example, your kitchen measures 6 feet wide by 8 feet long by 5 feet high which equals 240 cubic feet of air. Your vent must exchange air at least 15 times in one hour. Multiply the 240 cubic feet of air by 15 which gives 3600 cubic feet of air. CFM is measured in minutes. So divide 3600 by 60(one hour equals 60 minutes) which gives 60 CFM.
    Determine The BTU Units Your Cooker Produces
    You will find the BTU information on your cooktop’s manual or online. Electric cooktops should produce 3000 per burner and 18, 0000 BTU units for the gas tops.

    Multiply the BTU unit by 0.01 and add one to the result in step 1. If you have a four burner gas cooktop, it should be.

    18,000 BTU units by four burners (72000) BTU units multiplied by 0.01 to give you 720

    Add the 60 CFM to the 720 figure obtained above to give a total of 780 CFM
    The Duct Length Of Stale Air The Range Hood Needs To Overcome
    To understand how to measure the duct length, you should understand the capability of the stale air to move through the duct. There is a constant pressure inside every duct. When air moves through the duct, it encounters some static pressure resistance. Your exhaust fan should overcome the static pressure present in the duct.
    Here is how to calculate the equivalent duct length:
    • Identify the length of the duct run. You will need the measurements on the size, lengths, shape, turns and caps on the hood ranger.
    • For instance: 5 pipe length, ten elbow length, and 20 roof cap equals 35 CFM
    • Add the 35 CFM to the calculations from above (35+ 780) to get 815 CFM rating for your range hood. In compliance with the HIV building code, you will whether to install a Quiet range hood with a rating of 815 and above.

Conclusion

Calculating the CFM for range hood seems like a complex equation. However, you need to have your cooktop BTU measurement, the area the range hood will occupy, and the equivalent duct length range. Most of the information is available in the manual and the Internet. You can consult a licensed professional when in doubt. While at it, ensure you follow the building codes and regulations in your area.

We hope the tutorial was helpful and easy to follow. Feel free to comment and share!

How to Choose The Right Range Hood

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