Range Hoods: An Air of Confidence

Top Performers in Under-cabinet, Chimney-Style & Downdraft Models

The first range hoods that include a system that automatically turns on the units when it detects that you started to cook were introduced. Meanwhile, engineers and scientists are moving closer to approving the first standard for measuring a range hood’s efficiency in capturing pollutants.

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Range-hood manufacturers love to trumpet their models’ high blower speeds and unique designs, but five ventilation experts tell us that most consumers don’t bother to turn on their range hood until their kitchen is full of heat, moisture and smoke. All experts recommend that you turn on your range hood when you start to cook, even if you just heat water in a small pot. By turning it on when you start to cook, your range hood will create a better draft for proper ventilation, which will extract the air, moisture and smoke out of your home most effectively, experts say.

What would be even better is a range hood that turns on automatically. Previously, ventilation experts told us that the ideal range hood would be a model that turns on automatically when it detects that you started to cook. That’s why Elica’s Stream sensor system is so notable. As of press time, the system was expected to be available in March 2017 in the United States in five range hoods (starting at $999). Those range hoods will be compatible with Elica induction cooktops (starting at $1,999).

The Stream system’s sensors in the cooktop and range hood communicate with each other. Matt Holmes of Elica says that when you turn on a burner, the cooktop signals the range hood, which turns on and automatically sets itself at a ventilation speed that’s based on the size of the burner and how much power that the burner is capable of producing. As you continue to cook, the range hood continues to monitor the moisture and temperature and increases or decreases the blower speed as needed, Elica says. After you finish cooking, the range hood keeps its blower on until it senses that the moisture and temperature levels dropped to normal levels. It then turns itself off. If you prefer, you can take the range hood off autopilot and operate it as a traditional range hood.

Elica launched the range hoods and cooktops in March 2016 in Europe. Unfortunately, we were unable to find any independent expert in Europe who has used it.

Most manufacturers sell at least one line of range hoods (starting at $300, compared with $400 before) that includes a built-in heat sensor. These built-in heat sensors don’t communicate with a cooktop, however. Instead, the sensors monitor the temperature that’s above the cooking surface and turn on the range hood’s blower if the sensor detects that the temperature exceeds a certain level.

Unfortunately, only excess heat triggers a heat sensor. If you simmer a sauce on low, you might create a lot of vapors without producing much heat. In other words, if you aren’t creating enough heat, the range hood’s blower won’t turn on. By the time that it finally turns on, your kitchen already might be filled with heat, moisture and pollutants.

“We would really like to see it required one day that range hoods sense when a cooking burner is turned on and turn on automatically,” says Dr. Iain Walker of Lawrence Berkeley National Laboratory. “Most cooks don’t want to monitor their household indoor air quality. They just want their range hood to work. To make that happen is going to require some degree of automation.”

No other manufacturer tells us that it’s developing a similar system to Elica’s, but like Walker, we hope that such systems are common before long to reduce the chance that consumers might forget to turn on their range hood.

For now, Elica’s system works only with Elica induction cooktops. Gas and electric cooktop compatibility might come by 2018, Holmes says. (Elica still is developing gas and electric cooktops for the United States.)

We’ll be happy to see automatic sensors come to electric and gas cooktops, because they produce far more pollutants than do induction cooktops.

“In electric and gas cooking, the glowing red element and the naked flame produce a lot of the chemicals that we’re trying to get rid of, a lot of extra pollutants,” Walker says.

Meanwhile, an induction element doesn’t produce those chemicals.

CAPTURE THE HEAT. Years ago, experts at Berkeley Lab began to work with ASTM International, which is a standards organization, on the first standard for testing a range hood’s efficiency in capturing pollutants. That’s important, because the so-called capture efficiency of two range hoods can vary widely, even if the two range hoods have the same airflow.

Berkeley Lab started to develop the standard after conducting a study that determined that range-hood airflow often fell below advertised airflow rates and that, in some cases, less than half of the pollutants that gas burners produced were removed during operation.

“You could have a high airflow rating and poor capture efficiency,” Walker says. “The airflow rating doesn’t tell you everything that you need to know in determining how well the pollutants are captured and sucked up and sent out of the kitchen and outside. Capture efficiency is a much better metric for that.”

As of press time, the first of two ASTM committees was expected to finish reviewing the standard by Sept. 28, 2016. If the reviews go smoothly, a final version might be approved by the end of September 2017, Walker says.

After it’s approved, the test will become part of American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 62.2, which is a residential ventilation standard for buildings that are three stories or fewer. Any builder that builds a home in accordance with ASHRAE 62.2 will have to use a range hood that meets the minimum capture efficiency that’s in ASHRAE Standard 62.2.

Manufacturers still will be able to make noncompliant range hoods. Those range hoods just couldn’t be used when the 62.2 standard is required. Ultimately, Walker believes that capture efficiency will be another specification that manufacturers use in their marketing.

In developing the standard, Berkeley Labs analyzed the capture efficiency of dozens of range hoods.

“We found that there’s a big range in performance,” Walker says. “The good ones capture more than 95 percent of pollutants, but there are also terrible ones that capture just 50 percent. Some range hoods work very well at a lower airflow, and some don’t.”

Ideally, you want a range hood that has a high capture-efficiency rating and an airflow of less than 400 cubic feet per minute (cfm). Most building codes specify that if you install a range hood that has an airflow of at least 400 cfm, you have to install a dedicated makeup-air system to avoid backdrafting problems in your home. Walker hopes that the test standard will make it possible for consumers to identify range hoods that have high capture-efficiency ratings and low airflow ratings.

The scientists found that range hoods that are deeper so they come out farther from the wall than do others typically capture more pollutants. If a range hood doesn’t come out far enough from the wall to hang over a cooktop’s or a range’s front burners, then it typically has a much more difficult time capturing pollutants, particularly from the front burners of a cooktop or range, Walker says. Range hoods that have a large capture surface, rather than small capture surfaces that are targeted toward specific burners, also typically have high capture-efficiency ratings, he says.

You should keep in mind that a range hood’s capture-efficiency rating might not be the same as what a range hood captures in your kitchen, Walker says. Range-hood capture efficiency can vary from kitchen to kitchen depending on the range hood’s installation, how well that air flows through your duct and the layout of your kitchen, he says.

“If we say a range hood has an 80 percent capture efficiency, that does not guarantee 80 percent in your kitchen,” Walker says. “It could be a little higher, it could be a little lower.”

In other words, Berkeley Labs isn’t trying to predict the capture efficiency in your home accurately. It’s trying to develop a standard that fairly compares different range hoods.

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