Clearing the Air: Part 1

Expert tips to make the most of kitchen and bath ventilation
By Brian Wellnitz
July 31, 2012

Proper kitchen ventilation is the key to removing cooking smoke and odors from any home, especially in tightly built dwellings that include high-performance cooktops and ranges. Keep the following 10 expert ventilation tips in mind when planning your next kitchen design:

1. Vent the hood outdoors whenever possible so smoke and odors can be thoroughly eliminated from the home. This is the only way to guarantee removal of very tiny particulate matter, which can be 100 times smaller than a human hair.

Although recirculating fans also remove odors and particulate, they can recirculate up to 70 percent of the particulate back into the house. But like vented models, recirculating fans still provide a measure of odor filtration and protection to surrounding cabinets and additional lighting.

2. Select a range hood that is appropriate for the appliance and the client’s cooking style. Employ these general guidelines for approximating cubic feet per minute (cfm) air flow:
• For standard or conventional cooking equipment (less than 60,000 Btu for gas or electric cooktops), specify 100 cfm for every 1 ft. of width of cooking surface. For example, a 30-in. cooktop requires 250 cfm.

• For high-performance gas cooking equipment (more than 60,000 Btu), use 1 cfm for every 100 Btu. For example, 60,000 Btu requires 600 cfm.

• If the cooktop contains a grill, add 200 cfm to the total required.

• If the hood is rated at more than 300 cfm, the project may require a make-up air damper, depending on local codes.
If quiet operation is paramount, consider specifying an oversized blower. For example, 300 cfm might be adequate for the cook’s needs, but a range hood rated at 400 cfm produces less noise at a lower speed while providing 300 cfm. For even quieter operation, choose a hood model with a remote blower. Finally, select a Home Ventilating Institute (HVI)-certified hood to ensure the cfm and Sone levels match the manufacturer’s claim.

3. Select a range hood that adequately covers the cooking surface. At a minimum, the hood width should be equal to the width of the cooking surface, and the depth from front to back should cover the rear burners and at least 50 percent of the front burners. For clients who are avid cooks, consider installing a range hood that is 6 in. wider than the cooktop. Consequently, a 30-in.-wide appliance would be paired with a 36-in.-wide hood. (Also choose an appropriate filter: see below for a sidebar on filter types.)

4. Position the hood above the cooktop as close as possible to the manufacturer’s recommendation to increase smoke and odor capture while allowing adequate access to the cooktop.

5. Reduce drafts around the cooking surface that can blow smoke and heat away from the cooktop by eliminating ceiling fans and reducing drafts from windows or patio doors.

6. Install a duct that is equal to or greater than the size of the duct connector on the hood. Duct size is critical to the hood’s performance, so be sure the installer specs the proper size and does not crush the duct during installation. In addition, you can increase the duct size above the manufacturer’s instructions to boost the fan’s performance and reduce noise.

7. Prevent air dams that can occur when elbows are positioned too close together or when using sharp transitions. Keep 90-degree elbows at least 2 ft. apart; if that’s not possible, install a much larger duct size. Likewise, request that the installer install gentle duct transitions, which also prevent air dams and turbulence.

8. Make sure the backdraft damper opens and closes freely at the range hood. Inspect existing roof and wall caps to make sure nothing prevents damper movement.

9. Install a make-up air damper in tightly built homes. Make-up air dampers ensure there is adequate air supply throughout the home to allow the range hood to exhaust smoke and odors efficiently. They can be interlocked with the range hood and open automatically when the hood is turned on.

10. Consider convenience features that make meal preparation easier, such as lighting, timers and remote controls. Halogen is the most popular lamp type for range hoods because of its inherent brightness; LEDs are gaining popularity but high temperatures make most inappropriate for hoods. As the technology improves to accommodate higher cooking temperatures, consider LEDs designed for hoods that offer longer life spans and higher energy savings than halogens. Finally, remote controls make accessing the hood easy, and built-in timers provide added convenience.

See below for a sidebar on filter types and check back for Part 2 of this article, which will list 10 expert tips for optimizing bathroom ventilation.

—Brian Wellnitz has been marketing manager, Kitchen Ventilation, for Broan-NuTone LLC since 2008 and was senior product manager from 2007 to 2008. He joined the firm in 1997. Wellnitz has an MBA from Cardinal Stritch University in Milwaukee and a B.S. in Electrical Engineering Technology from the Milwaukee School of Engineering.


In addition to ensuring proper hood selection and installation, choosing the right filter is also critical. Following is a list of the common filter types for kitchen range hoods. Consider one that best meets your client’s cooking needs and the cooktop’s performance.

Charcoal filter: Bonds with particulates to remove odors from the air; generally needs to be replaced every 30 to 90 days. Typically used in conjunction with grease filters.

Baffle filter: Sets on an angle to the incoming air to collect grease; made of stainless steel; requires regular cleaning to control oil buildup. Operates best at higher cfm.

Oil cup (no filters): Requires grease to be pulled into blower where it condenses into removable cups; must be emptied when full. Cleaning typically requires disassembly of some components.

Aluminum mesh filter: Catches grease and oil in a fine aluminum mesh; works well at all cfm levels; require regular maintenance to work properly. Dishwasher safe.

Stainless steel mesh: Catches grease and oil in a fine stainless steel mesh; works well at all CFM levels; requires regular maintenance to work properly; does not discolor after repeated washing. Dishwasher safe.

Combination baffle and mesh filters: Includes the benefits of baffle and mesh filters. Offers high grease removal and good filtration at all speeds.

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