When you consider all the things that affect the air quality inside your home while you’re cooking, having a quality range hood makes perfect sense. All the gunk – steam, smoke, food particles, grease – that splatters on your stove can wind up in your air. A good range hood sucks all of it up and filters it out, preventing it from settling into the fabrics in your house and lingering forever. We’ve got lots of information for you about how to choose a range hood. Here, we specifically discuss CFM requirements for your kitchen and cooking style.
Table of Contents
- What is CFM for Range Hoods?
- Advantages and disadvantages of too small or too large exhaust air volume
- How to Calculate the Right CFM for Your Home
- Ducted Range Hoods for Electric Cooktops
- Ducted Range Hoods for Gas Cooktops
- Room Size for Range Hoods
- Range Hood Ductwork
- How to Decide On A CFM Number
- Other Factors & Issues to Consider
- The Dangers of Not Using Your Kitchen Exhaust Fan
CFM means cubic feet of air moved per minute. Simply put, it’s the amount of air a ventilation hood fan is capable of removing through its filter every minute. The fan has to be powerful enough to cover the cooking area and suck up all that potential pollution, but not so loud you feel like you’re cooking next to a jet engine. Therefore, when purchasing a hood, you should look at CFM, but it is not the bigger the better. You should buy it according to your actual situation and living conditions.
1.When the exhaust air volume of the range hood is too small, the speed of removing the oil fume is slow, or the oil fume is not drawn cleanly. And the oil fume increases with the use time. After the suction of the machine is weakened, the fumes are more unclean.
2.When the air volume of the range hood is too large, it will take away the surrounding oxygen and have a certain impact on the gas flame, and also take away part of the heat. Excessive air volume has higher requirements on the range hood motor, so It increases the noise and affects the comfort of cooking.
You can figure out your CFM requirements in several different ways, considering the size of your range, the size of the room, the layout of your kitchen, and the different types of range hoods you’re considering. Here’s what you need to consider:
✦ Type of range hood
✦ Type of stove – electric or gas
✦ Room size
Ducted Range Hoods for Electric Cooktops
Wall-mounted & Under-cabinet range hoods – 100 CFM for every linear foot of cooktop. Most common types of cooktops measure 30 inches wide, or 2.5ft. To meet the recommended CFM requirements, you’ll need a range hood with 250 CFM.
Example: 2.5ft wide cooktop x 100 CFM = 250 CFM
Island hoods – 150 CFM for every linear foot of the cooktop. Due to the open nature of a kitchen island stove, you need extra power. As a general rule of thumb, for the same 30” cooktop, you’ll need a range hood with 375 CFM.
Example: 2.5ft wide cooktop x 150 CFM = 375 CFM
While we’ve modeled on an average-sized cooktop, your stove may be as narrow as 20 inches or as wide as a 60-inch commercial model. Measure or check the specs in your user manual to be sure.
Gas stovetops can heat up the room more than an electric cooktop. It’s wise to choose a range hood fan with higher CFM if you have a gas stove.
Heat output is measured in BTU, which stands for British Thermal Units. One BTU is the amount of energy needed to heat or cool 1 lb of water by 1°F at sea level. Each burner on your cooktop has a BTU rating (check your user manual).
To calculate the CFM for a gas stove, add the BTU ratings for all burners. Typically, 5,000 to 15,000 per burner is common. Divide your gas cooktop total by 100 to figure out the CFM you need.
If the current total BTU is 35000.
Example: 35000 BTU ÷ 100 = 350 CFM range hood fan or higher
Next, consider the size of the room. The trend toward open kitchen layouts and higher ceilings influences the extent to which uncaptured particulates can travel. An effective range hood should be capable of exchanging the air in the kitchen every 4 minutes (15 times per hour) by volume to keep your indoor air clean.
For example, if you have an open concept home, your kitchen may be located in a 20’ x 20’ room with 10’ ceilings.
20 ft x 20 ftx 10 ft = 4,000 cubic feet
To figure the CFM needed for your size kitchen, divide the cubic feet by 4 (minutes)
4,000 ÷ 4 = 1,000 CFM range hood (or higher)
Finally, you need to consider your ducts. Since your fan must pull the air through the filter and out through the duct to the vent, the length of the ductwork is an additional consideration. Common ducts are round and about 6 inches in diameter. For each foot of pipe, add one additional CFM. If the pipe has elbow bends, add 25 CFM for each, plus 40 CFM for the cap.
With all the different factors to consider, which calculation is the right one? Simple. Pick the biggest CFM number. Look for a range hood that offers all the power you need, with the quiet operation you’ll want to save your sanity. Other features to look for include variable fan speeds, dish-washer safe baffle filter, touch panel operation, energy-saving LED light, and of course, a hood style that fits your aesthetic.
✦ No outside ventilation – in some cases, such as stoves located on the interior wall of an apartment building, exterior ducting is not possible. In that case, you’re likely to have a ductless range hood, which is essentially a fan that pulls cooking air through a filter and expels it back into the room. These are not all created equal.
✦ Your range hood needs to be cleaned – Range hoods need regular cleaning to be effective, and filters need to be replaced or cleaned now and then.
✦ All noise, no pull – Some kitchen ventilation fans are ineffective. They may be loud, but they don’t really accomplish anything. They simply don’t have the CFM to do the job.
✦ You forget to turn it on. For best results, turn on the fan 10-15 minutes before you turn on the stove. Then leave the fan running for about as long after you turn off the stove. This added running time will improve filtration capabilities and reduce the number of contaminants you may inhale.
Indoor air pollution is a health risk. In the short term, pollutants can trigger asthma attacks, irritate the eyes, nose, and throat, and cause headaches, dizziness, and fatigue. Temporary effects usually go away on their own with limited exposure, but over the long term, living in a home with a poor ventilation system can result in chronic respiratory diseases, heart disease, cancer, and even death.