How Powerful Should a Range Hood Be?
Question: "I am putting in a Dacor Epicure cooktop with approximately 85,000 Btus. I want to use a Zephyr Milano glass canopy island hood with a capacity of 715 CFM (cubic feet per minute). Do you think this will be a problem?"
Answer: More than likely, a cooktop with 85,000 Btus will need a ventilation hood with greater power than 715 CFM. Here's why: Dacor's Epicure line of cooktops has gas burners. And when dealing with gas burners, there is a simple ratio to consider when buying a range hood for your kitchen.
"A rule of thumb is 100 (Btus) to 1 (CFM), so a cooktop with 85,000 Btus would require a ventilation hood with 850 CFM or more," says Bob Lewis, Dacor's assistant vice president of product development.
One other thing to consider is that island hoods typically need extra ventilation power compared to range hoods that are situated against a wall. "Island installations have more cross drafts to contend with," said Lewis. "Wall mounts are relatively protected which allows the motor to establish a consistent airflow pattern." So for island hoods, there's a chance that it will need more power than 1 CFM for every 100 Btus.
You might be able to get away with a range hood that doesn't quite match your cooktop's full heat potential if you never use all the burners at once or you usually use low heat when you cook. But if you're constantly cranking up the Btus, you'll want to follow the 100:1 ratio. (Although if you're purchasing a cooktop with 85,000 Btus, your cooking style probably is more professional and takes advantage of all the heat your appliance can generate.
When it comes to finding range hoods for electric and induction cooktops, there isn't a handy rule of thumb to guide you. The 100:1 ratio won't work because electric and induction cooktops measure energy in kilowatts instead of Btus. Even if you converted the units (1 kilowatt equals roughly 3,400 Btus), you would still need to account for the fact that electric and induction cooktops distribute heat more efficiently than gas cooktops. Since less heat is escaping into your kitchen with electric and induction cooktops, they require less ventilation than gas cooktops do.
How much less should be determined on a case-by-case basis, since heat distribution efficiency can vary by manufacturer. So it is best to consult with the manufacturer of your electric or induction cooktop as to what type of ventilation unit you'll need.