Building codes require that all kitchens be equipped with a kitchen range hood to remove moisture, odors, fumes, and heat from the immediate area during cooking. To comply, builders have various options that can be grouped into two categories: exhaust fans that vent outdoors and exhaust fans that don't.
The best kitchen ventilation system includes an inline exhaust fan that vents outdoors. An inline exhaust fan pulls polluted air out of the kitchen through ducting and exhausts it through a vent in the roof or an exterior wall. In contrast, kitchen exhaust fans that don’t vent outside simply recirculate the polluted air around in the kitchen. Non-venting fans also are noisy, which can deter homeowners from using them.
A kitchen ventilation system that includes an inline exhaust fan typically has six components—a hood, a backdraft damper, ducts, a duct attenuator, a fan, and a termination device:
Hood. The hood covers the cooking area and extends beyond it by about 3”. It can be an exposed stainless steel hood, a built-in hood liner with a decorative surround, or a filter grille. The first two options are most commonly used. A filter grille is usually chosen for aesthetic purposes for use over an island stovetop.
Backdraft damper. A backdraft damper should be installed right next to the hood or grille. It keeps outside air from flowing backward into the home.
Ducts. Use steel or aluminum ducting that's UL listed for residential kitchen exhaust. The duct run should be as short and direct as possible, because the longer and more complicated the duct run, the more restricted the airflow will be. Also, seal all duct connections and seams with mastic and UL 181 rated foil tape to prevent leaks.
Duct attenuator. A duct attenuator, or "silencer," should be installed between the hood and the fan to muffle the sound of the fan.
Fan. The inline fan is installed within the duct run, hence its name. The fan will be equally effective at any spot within the duct run; however, the quietest position is as far from the hood as possible, which is why the fan is typically located in the attic.
Termination device. Either a roof cap or wall hood is needed to terminate the duct. It must be located at least 3' from any other opening, so the exhaust doesn’t travel back into the home. Also, the penetration around the termination device must be sealed and flashed properly to prevent water intrusion.
Inline exhaust fans are quiet, reliable, efficient, and economical. They keep kitchen counters, walls, floors, and furniture cleaner longer than non-venting fans. ENERGY STAR-qualified models, which are more than 50% quieter than standard models, are available. For more information about inline kitchen exhaust fans, visit the ENERGY STAR site.