Range hoods are very important features in a kitchen. Located at or over your cooktop, they function to expel grease vapor and cooking smells from your kitchen to the outdoors. A lack of adequate venting over time will cause a slow build up of layers of grease and odor. Several factors affect the type of range hood best for each kitchen.
Check with your local municipal authority as to the minimum venting requirements for range hoods in your area. Though some building departments do not require you install a range hood over your cooktop, having adequate venting is important if you like to fry foods or cook with fragrant spices for long periods of time.
A range hood should be as wide or a little wider than your cooktop surface. The fan power of your range hood, or its CFM (cubic feet of air per minute) should directly correlate to the BTU (British thermal unit) output of your range. Typically, for every 100 BTUs of gas output, you should provide 1 CFM volume airflow from your range hood. An electric range will require less CFM than a gas range.
Wall-Mounted Range Hoods
Wall-mounted range hoods are the most common type of range hood available, and they come in many different styles, from basic functional range hoods to large decorative hoods. Because cooking smells and steam travel upward, a wall-mounted range hood that sits directly over the cooking surface is very effective at extraction. Wall-mounted range hoods can also be hidden in upper cabinets or combined with a microwave over your range.
Downdraft Range Hoods
Downdraft range hoods are used when an range hood cannot be mounted on a wall over the range, such as for a cooktop in a free-standing kitchen island or where a visible wall-mounted range hood is not desired. Typically integrated into the cooktop surround itself, a downdraft range pops up when in use to extract cooking fumes at a few inches above the cooking surface. Downdraft range hood fans are located in the kitchen cabinetry, and they are ducted down into the kitchen cabinet and out an exterior wall.
For all range hood types, duct work should be routed to the outside wall in as direct a path as possible. The more bends that a range hood duct has to make to exit through a wall, the less effective the fan will be in extracting cooking fumes. Ducting is available in several types; the most common is a round flexible duct. Rigid flat duct is also available, and its main benefit is it can fit easily in the depth of wall framing.
In a situation where you are not able to vent your range hood directly outside, you can install a recirculating range hood. Carbon filters within the range hood remove the grease vapor and cooking smells from the air, then the range hood ejects the warm air back into the room. The carbon filters need to be changed periodically to remain effective.