Before finding the answer, how many cfm do I need for my range hood we must know about range hood first.A range hood is an exoteric component or structure of a kitchen, especially today’s generation wants to remodel or build a kitchen with fresh air quality. Range hood inhales the unpleasant odor and bad smoke during cooking and exhales the bad air exterior.
This how range hood enhances indoor air quality. Establishing a range hood depends on some factors. Otherwise, the range hood can not work according to its true potential.
Here in this writing, we’ll provide a short brief on every factor related to choosing a suitable range hood for our kitchen. During discussing the elements, you’ll easily find out what can ensure you the best exhaling from your range hood. Let’s get started.
Contents
What Do We Mean by CMF?
To determine the airflow capacity of range hoods, there comes a term named Cubic Feet per Minute (CFMcfan can exhale outside per minute. That means the smaller or lesser the number of CFM will be. The less air will be passed through the range hood per minute. CFM determines how powerful the fan exhales the air.
For exquisite sizing, it’s essential to know, how do I calculate for kitchen exhaust fan. Here everyone should know the proper way of calculating the CFM and determine the fan size.
Determining the Exact CFM for Range Hood
Determining the CFM for range hood is not a difficult task to do. But it has to be done mathematically. Here, we become acquainted how to measure a perfect CFM for our home kitchen. There is no way to choose a CFM as you want. Because less power full exhaust fan cannot exhale the more air than its capability. Also, a more substantial exhaust fan needs a larger range hood. If you don’t want to measure the CFM and buy a larger range hood, that may spoil your kitchen’s beauty.
Determining the CFM based on Kitchen Size
how much cfm do I need kitchen is a common question. Also, the important one for those who want fresh air quality in their kitchen. To determine the CFM for the kitchen, everyone should consider the size of the kitchen. Not a tough one to understand because larger kitchen needs more air to be vented.
The range hood should have to exchange the kitchen air 15-20 times in 1 hour. For example, your kitchen’s width, length, and height are 16′, 16′, and 8′ means the total dimension of your kitchen is 2048 cubic feet.
Now, multiply total cubic feet with the total number of air exchanges per hour. 2048 cubic feet x 15= 30,720 cubic feet. This is the number of total amounts of air moved by the range hood in per hour.
Now divide the total amount with 60 minutes and will get the value per minute. 30720 cubic feet/ 60 minutes= 512 CFM. So, you need a minimum of 512 CFM for yourkitchen according to your kitchen size.
Determining the CFM based on Gas Stove
To keep the inside air fresh, the range hood must need to ventilate the interior air, especially the heat generated heat from the stove. In the short term, CFM depends on the total burner you are using a gas stove. Usually, the electrical range produces less heat than a gas stove.
The system is, you have to determine the CFM for your range hood according to the sum of all BTU ratings for all gas burners. Now, first of all, you should know what the BTU stands for?BTU ordains the amount of heat necessary to increase the temperature of one pound of water by one-degree Fahrenheit. There is a rule for determining the exact CFM according to BTU, and it is 1 CFM for 100 BTU.
BTU ratings for all burners have a range. Mostly between 4,000-16,000 BTU. But most burners offer an average of 10,500 BTU. Suppose you have a gas stove with four burners. Every burner has a BTU of 10,500. So, for four burners, it will be 42,000 BTU. Ow divide the number with 100, and you will get the required CFM for your kitchen. 42,000/100= 420 CFM. Your kitchen will need a minimum of 420 CFM for good exhaling.
Determining the CFM based on Range Hood Duct work
The range hood cfm calculator depends on some factors. Among them, duct work is the most important. It indicates the shape, size, length, and cap on the vent hood duct work applies some resistance, which decreases the amount of air from the true potential of a range hood.
Usually, we take 1 CFM per foot of around 8 inches diameter smooth metal pipe, 30 CFM for each elbow, and 55 CFM for roof cap. For example, your vent pipe’s length is 15 inches and has three elbows and a roof cap. 15 CFM for pipe length + (30x 3) CFM for elbows +55 CFM for roof cap = 160 CFM.
Determining the CFM based on Stove Size
Usually, there has a basic rule of thumb for determining the CFM for stove size. We have to put 100 CFM for every 12” of stove width. Now the question is, how many cfm do I need for a 36 gas range? If 12 inches stove needs 100 CFM, then 36 inches will need 300 CFM.
Final Calculation
Yes, you have to determine all the factors and find out the maximum number of CFM. Suppose your CFM amount is 512 from kitchen size, 420 CFM from BTU, and 300 CFM for stove size. Among these three, you have to choose the maximum amount of CFM, which is 512. Now adding 160 CFM for range hood ductwork, you’ll get the actual amount of CFM you required.
512 + 160 = 672 CFM ~ 700 CFM. You have to select a round figure. So, the minimum CFM you need is 700 CFM.
CFM Calculation on Commercial Kitchen Hood
Commercial kitchen hood cfm calculation depends on the on-duty time of the gas or electric stove. For commercial range hood, it is a must to ensure a perfect range hood because smoke, grease, and solid fuel can cause dangerous creosote buildup inside the vent and cause accidents if their range hood doesn’t have the perfect CFM for exhaust fan. Let’s see the classification of the commercial range hood and their suitable CFM.
- Light Duty: For light-duty appliances like gas and electric and convection ovens and steamers. For these kinds of light-duty appliances in the kitchen, we need CFM between 150 CFM to 300 CFM.
- Medium Duty: Appliances for electric and gas hot-tops, fryers, griddles, rotisseries, conveyor ovens, and gas/electric pasta cookers all are considered as a medium-duty. For this appliance, you need a minimum 150 to a maximum of 400 CFM depending on their using time and how many of them you are using.
- Heavy Duty: Appliances like electric and gas underfired broilers, gas and electric open burner and stove, salamanders, and woks are known as heavy-duty kitchen appliances. For these heavy-duty kitchen appliances, we need at least 200 CFM to maximum 400 CFM depending on our using time and number of appliances.
- Extra-Heavy Duty: Solid appliances such as solid fuel, wood, charcoal, mesquite, and briquettes, which generate an enormous heat source for cooking, are labeled as Extra-heavy-duty kitchen appliances. For these kinds of appliances, we need at least 350 CFM to a maximum of 550 CFM.
Data Table for Commercial CFM
| Model of Hood | Light Duty Appliances | Medium Duty Appliances | Heavy Duty Appliances | Extra-Heavy-duty Appliances |
| Wall-Mounted Canopy | 150-200 | 200-300 | 200-400 | More than 350 |
| Single Island Canopy | 250-300 | 300-400 | 300-600 | More than 550 |
| Double Island Canopy | 150-200 | 200-300 | 250-400 | More than 500 |
| Eye Brow | 150-250 | 150-200 |
Recommendation for CMF
If you need any suggestion for our home ventilation, we should ask it to HVI (Home Ventilating Institute). It is an entirely non-profit organization structured by the top-class venting appliances companies to provide a model on any kind of ventilation. According to HVI, there have some basic numbers of CFM for kitchen range hood.
- 30-inch Range Hood: It is the most popular and standard size in the range hood industry. The 30″ wide range hood needs a minimum of 100 CFM. But the recommendation is 250 CFM for it.
- 36-inch Range Hood:For a 36-inch range hood, the minimum number of CFM is 120. The recommendation is 300 CFM.
- 48-inch Range Hood: 160 CFM is the minimum for it. The recommendation is 400 CFM.
Negative Air Pressure
First of all, we must know what negative air pressure is. We all know the range hood ventilation system is used for exhausting the odor and gases from the kitchen. Negative air pressure occurs when makeup air is bought out from outside has no balance with the air pushed by the vent hood.
This imbalance of the exhale and inhale of kitchen air can cause back drafting. For back drafting, exhaust air that is supposed to become out gets pulled back into the kitchen’s interior being pushed outside.
So HVI recommends for a makeup air for whom has range hood with 600 CFM. It is mandatory for them. This problem happens in a newer home that has made tightly and compactly. It isn’t easy to bring in air from the exterior to establish balance in this kind of compact apartment or house. Older houses are not this compact. So, they have no issue with negative air pressure.
To overcome this problem is newer houses, we have to install a makeup air system, which is massive and costly. This makeup air system is a motorized damper that connects to the range hood. As soon as the range hood turns on, the motorized damper exposes and allows air from outside.
FAQ About How Many CFM Do I Need for My Range Hood
Is 400 cfm enough for range hood?
We have discussed the CFM calculating above. For knowing the exact CFM, we determine the CFM value from kitchen size, BTU of stoves, stoves size, and range hood ductwork. Find out the maximum CFM value among the kitchen size, BTU of stoves, and stoves sizes. Now add the range duck hood CFM with it. The total value is your CFM.
Suppose your CFM amount is 512 from kitchen size, 420 CFM from BTU, and 300 CFM for stove size. Among these three, you have to choose the maximum amount of CFM, which is 512. Now adding 160 CFM for range hood ductwork, you’ll get the actual amount of CFM you required.
512 + 160 = 672 CFM ~ 700 CFM. You have to select a round figure. So, the minimum CFM you need is 700 CFM. If this value comes under 400 CFM, then 400 CFM is enough for your range hood.
how do I calculate cfm for kitchen exhaust fans?
For calculating, you have to determine the CFM value for kitchen size, CFM for BTU of stoves stove sizes, and range hood duct work. This how you can get the CFM for kitchen exhaust fans.
You also see this this video
Is it essential to my range hood to be wider than the cooktop?
Yeah, it is better to have a range hood 1.5 times wider than the cook top. This is especially for the induction cooktops. For instant, if your cooktop is 50 cm wide then your range hood must wide at least 75 cm. also for any kitchen island which has induction cooker, there needs a free- hanging hood that has to be twice as the entire cooking area.
Final Note
I hope you have a clear idea about how many cfm I need for my range hood.When you need it for your build kitchen, just try to follow the rules of HVI and recommendations. Moreover, the exhaust pipe’s turns at the top, quality of ducting, vent cap, and vent reducer can affect the exhaust fan even if it has the recommended CFM.