Improved Ventilation Enhance Kitchens

Kitchen experts and housing professionals agree that kitchens are especially enjoyable for family and guests when they are bright, cheerful and free of cooking odors, heat and humidity.  Yet, cooking in the kitchen generates a great deal of heat, steam, grease, smoke and odors that need to be ventilated to clean the air and to prevent harm to the home.  You shouldn't be able to smell dinner from every room in your house; otherwise, even when it is not mealtime, your house, clothing and furniture will reek with a stale odor. 

Cooking generates heat and modern professional-type ranges generate even more.  It is not uncommon for a range to have four burners, each generating 15,000 btu's of heat (total 60,000 btu's) along with an oven or broiler adding even more.  Yet a typical four-ton residential air conditioner is only capable of removing 48,000 btu's of heat per hour from the home. Clearly, the air conditioner will be overtaxed without supplemental ventilation.

Cooking also vaporizes oil and water contained in food and forms an extremely tough film that sticks like glue to everything it comes in contact with. In fact, home cooking can produce over a gallon of vaporized grease per year and this grease needs to be removed from the house.

Nitrogen oxides form when fuel is burned at high temperatures and is one of the main ingredients involved in the formation of ground-level ozone, which can trigger serious respiratory problems.   According to the EPA, the primary sources of nitrogen oxides are motor vehicles, electric utilities and other industrial, commercial and residential sources which burn fuels. The kitchen, with a gas oven, produced levels of 32 ppb, or twice that of outdoor concentrations.

Kitchen ventilators, commonly called range hoods or "hoods" are among the most important appliances in the home. While they remove grease, heat, moisture, cooking odors and combustion gases from the air, they also help protect a family's health and make the kitchen cleaner, safer and more comfortable.  Some range hoods merely filter the air, but most are connected to ductwork behind a wall, ceiling or floor and vented to the outside.  In years past, vent fans were simply a motorized fan mounted in a wall opening, but no more. Today, kitchen ventilation products are going high-tech.  The newest ventilation systems offer a wide array of features including delayed shutoff timers, clean-filter indicators along with sensors that automatically adjust blower speed and volume to the heat output of a range.

Homeowners may choose from a variety of styles and designs, but the only type that can be 100% effective in eliminating pollutants is an overhead canopy hood with a high-performance blower.  In order for a ventilation system to effectively remove all cooking byproducts, four things are required:

1. A canopy of sufficient size and design to hold contaminants prior to removal.

2. A blower system capable of removing heat, steam and odors.

3. Filtration capable of liquefying and containing cooking grease.

4. Ductwork of the proper size and configuration to vent the byproducts outside.

Hundreds of models are available but custom-built models can be made to hold inserts. Most include lighting and many offer additional accessories to make cooking easier.  Let's take a look at what else you might be looking for in range ventilation hoods besides whisking away odors.

Efficiency

A good range hood should be powerful enough that it reduces greasy buildup that can accumulate on cabinets and kitchen appliances, and strong enough to pull out contaminants that occur naturally while cooking.   An effective way to check on a model's efficiency is to look at the manufacturer's specifications.  A CFM (cubic feet per minute) rating tells you the amount of air that is moved per minute in cubic feet.  The amount of air that the unit will actually move once installed in your kitchen will depend on how airtight your kitchen is.   This rating varies significantly between models.  An efficient ventilation hood should be between 250 and 650 CFM, whereas a less effective model may only be 190 CFM or less.  A Professional restaurant style ventilation hood can even be as high as 1200 CFM, if you are willing to pay the price.   The presence of a barbecue grill, griddle or wok may require additional CFM to ensure proper ventilation.   The type of filtration methods can also reduce CFM.

CFM output is also affected by the type of blower used in the range hood.  Some use blowers in which a squirrel cage wheel produces a high-efficiency air flow with low resistance in the duct with relatively quite performance.  Others use a propeller-like fan that is more turbulent and noisy with high resistance in the duct, resulting in a huge loss in CFM output.

Most hoods are available with several different size fans or blowers.  Many models offer fans with multiple or variable speeds. Several models have gone high-tech and automatically adjusts the fan speed based on actual heat temperatures.  But keep in mind, bigger is not always better.  Ventilation systems need to be properly sized.  Oversized systems can be powerful enough to pull exhaust fumes out of a fireplace, woodstove, water heater or furnace.  "Backdrafting" could expose occupants to carbon monoxide and other pollutants.  A simple test to see if this is happening is to use a stick of incense or a smoking match. Close all interior doors except those between the kitchen and the combustion device.  While the exhaust fan is running, watch to see whether the smoke rises up the flue or is drawn to the kitchen ventilation system.  There are various solutions to backdrafting -- but the best solution is to not oversize the kitchen ventilation system.

However it is also very important to place emphasis on noise levels of range hoods, not just CFM of air evacuation.  The noise level of vent fans is measured in sones, which is a subjective unit of volume, equivalent to the sound of a pure tone of 100 hertz at 40 decibels.   The higher the sone rating, the louder the fan. One sone is the equivalent of a quiet refrigerator in a quite room. Typical sone ratings run from 2 at low speed to 6 at high speed.  The Home Ventilating Institute (HVI) recommends that kitchen ventilation fans should not be louder than 9 sones.

Another design feature that also affects sound levels is the location of the ventilator's motor and fan.   Integral ventilators have the fan and motor in the hood area.  A remote ventilation hood are located somewhere "up" the exhaust line, perhaps on the exterior wall, attic or even on the outside roof. There are two reasons for installing a remote blower; to save space inside the kitchen and/or for more power.  For downdraft installations, the provides extra space in the cabinets where an internal blower would take up much of the room.  Remote ventilators also tend to be less noisy because the motor is removed from the inside of the house, but you will still hear the noise caused by the air ventilating.  The majority of the noise generated by high capacity range hoods is not caused by the blower itself, but by the air moving through the filters and ductwork.

Types of Ventilation Systems 

The most effective type available is UPDRAFT ventilation (overhead hood).  It collects and removes cooking vapors several feet above the cooking surface taking advantage of the fact that cooking vapors naturally rise.  Another ventilation type is DOWNDRAFT ventilation.   These units are often selected when overhead types are impractical to install.   They conserve overhead space by venting the vapors and odors downward rather than up.  Downdraft ventilators are often utilized in island or peninsula installations because they're unobtrusive and create little interference with the overall kitchen plan.   In downdraft ventilation systems their fans are located at the surface of the range or cooktop and draw steam and grease downward and out of the kitchen via ductwork placed through the back of a base cabinet or even under the floor.  Unfortunately, in many downdraft installations, valuable cabinet space is lost -- but this varies greatly based on the model selected.  While downdraft systems are great for exhausting air around island cooktops and avoiding the problems of an overhead hood, they are less efficient in removing the steam from taller pots and they won't capture cooking vapors that aren't close to the ventilation intake.  Smoke from overheated oil or burned food is also not captured well with downdraft systems. 

Hood Styles 

There are different options that can accommodate the style, function and size specifications of your kitchen.   These options include:

Under Cabinet wall-mount canopy

This style is the most common and thus the one having the widest variety of color, size and feature options. Under cabinet models are generally easier to install, but still require some electrical and need ventilation ducting installed.  Under Cabinet Hoods have a price range between $200 to $900.  These are UPDRAFT ventilation.

Liner Insert Vent Hoods

A liner insert is a popular designer option because it assimilates the hood into custom built cabinets for a clean, uniform appearance.   The decorative hood can be created out of wood, plaster, tile or metal and be made to any desired shape. The liner provides an inner canopy, complete with blower system, switches and lighting and allows a kitchen designer to be totally creative in building a focal point for a signature kitchen.  Liners are sold in standard pre-fabricated sizes, but your kitchen designer or cabinet maker can ensure that you purchase the correct liner since they can be ordered to fit any custom hood.   Liner Insert Hoods  have a price range between $300 to $900, plus the price of the hood's cabinet and installation.  These are UPDRAFT ventilation.

Island or Peninsula Vent Hoods

Island vent hoods can be a stunning design focal point.  When your range or grill is built into an island, the peninsula vent hood with chimney  is probably your most viable option.  These vent up through a chimney and require ducting that runs above your ceiling to an outside wall.  Ceilings may need support reinforcement -- local building codes will dictate. Peninsula Vent Hoods with chimneys have a price range between $1200 to $2200 and up.   These are UPDRAFT ventilation.

Wall Mount Hoods

Wall chimney models go on a wall where there are no cabinets. These units are larger and heavy and accordingly, require specialized installation by a professional.  These specialty wall-mount canopies are very popular when a more dramatic look is desired.  Despite being a more expensive investment these models offer much in terms of quality and design. If you've invested in powerful cooking equipment you will need to match that power with the holding capacity of a large canopy. Hoods with deep canopies are able to trap more odor and smoke. They can also make a defining statement in your kitchen.  Wall Mount Hoods have a price range between $650 to $1800 and up.  These are UPDRAFT ventilation.

Downdraft models

The downdraft design arrests steam and odors at the cooking surface, pulling them down and out of your kitchen.   This ventilation method is generally incorporated as part of the cooktop. Downdraft models can cost anywhere between $500 to $2000, but remember you are buying a cooktop and a venting system.  Jenn-Air, the brand that invented downdraft ventilation, is well know for this design.  Downdraft vents are favored by some kitchen engineers because they keep the room open and eliminate the need for a more costly overhead hood.   While these venting systems have appeal for their uncluttered look it is to be noted that downdraft models have difficulty removing smoke.  This is not to say that they don't have a high CFM rating,  just that smoke is best captured from above.   Some downdraft models have a telescopic chimney or vent to aid in capturing smoke.

A newer type of downdraft ventilation  is a Pop-Up countertop level ventilation system.  These models are retractable and lie flush with the countertop until needed.  Many are motorized and disappear out of sight when not in use.  These pop-ups models are an improvements over flush-mount designs because of the location from which they draw the air.   However, several pop-up models are a low profile and can disrupt the heating process by pulling fumes away from the heat source. Several other models telescopes up a full 10" from behind the cooking surface, drawing heat and fumes from the cooking vapors, not at the heat source.  

What Size Canopy to Chose

The size of the hood is determined by the appliance to be vented.  For cosmetic and economic reasons, most range hoods are selected to match the cooktop in width. This lines up the range hood with the cooktop for a cleaner look, especially where cabinetry will be abutting the cooking area.  This is considered to be the MINIMUM width.

Color

Range hoods, more than any other kitchen appliance, contribute to an overall sense of style to a kitchen, while performing a vital function.   Hoods may reflect a traditional or contemporary look while others prefer a clean, built-in-look while a professional style kitchen calls for stainless steel which says "high end" and is an increasingly popular choice. Although not widely available, copper is another metal finish option. This route would require custom ordering your hood from a copper craftsman.

Range hoods are commonly available in black, white, bisque or almond.  For those with more daring taste, hoods are also available in custom colors and textures.  Imagination is the only limit! 

Features

Fan Speed - look for models with 3 or more speed settings or one that has variable speed control.

Light - having your range brightly lit is ideal while cooking. Look at the number of lights and the light settings.  There should be at least low and high settings for brightness. What is the recommended wattage? What type of bulbs does it use - halogen, incandescent or fluorescent? Some higher end models even have infrared warming lights to aid in keeping food warm before serving.  An additional thing to look for is how visible the lights are. Are the lights recessed and only visible under the hoods? Halogen lighting is becoming more and more popular since its inception.

Easy Cleaning - it is helpful when you can easily snap apart the housing of your hood in order to clean it. Cleaning the blower housing should be done with sap and hot water or in a dishwasher. Does the model have removable filters? Are they dishwasher safe?

Ducting - can it be ducted through the side and the back? Which does your installation require?

Noise Factor - Turning a deaf ear to the kids should be a matter of choice, not an appliance-induced handicap.  The quieter the range hood, the better. Manufacturers offer high quality lines of hoods, rated at about 600 CFM, that are very quiet.  Many mid-level lines that are rated at 350 CFM are just as unobtrusive. Lower-end series hoods that are rated around 200 CFM and below are not as quiet. Again, you have to pay more for quality.

Installation

Follow the manufacturer's recommendation for installation,  particularly the height specifications. The lower you can mount your hood, the more effective it will be.

Ensure the range hood is in proportion to your cooking surface.  If your hood doesn't cover the entire stove, steam and heat will escape. The most common widths for hoods are 30 and 36 inches. Other sizes are available. They start at 24 inches and increase in 2 inch increments.

Make sure you have sufficient venting power. As previously mentioned, look at the CFM rating.

Duct work should be metal and have smooth walls. Fewer bends and joints will ensure that there is less grime buildup. Planning your kitchen with the range and hood on an outside wall allows for more direct ventilation.  The minimum size duct allowed on most range hoods is 3 1/4" x 10", which is equivalent to 6" round. Vent pipes should be no smaller than 6" in diameter.  For most efficient airflow, the length of the run should be kept to a minimum, as well as the number of elbows and transitions.   Remember that 45-degree turns are always better than 90-degree turns.  A 15" straight section should be installed between transitions whenever possible because elbows and transitions adjacent to one another will cause significant reduction in performance.  When configuring a system for high-altitude installation (above 5000 feet), estimate a 20% reduction in CFM performance.  Ductwork should ALWAYS be metal, not plastic!  Ducting must always be vented to the outside, never into a closed area such as an attic or basement. 

Have a back draft damper installed, especially in cold weather installations to minimize backward cold airflow.  Additionally, a non-metallic thermal break is needed to minimize conduction of cold airflow through the ductwork.   The damper should be in the cold air size of the thermal break and the thermal break should be as close as possible to where the ducting enters the heated portion of the house.

Three things to Avoid

Really cheap under-cabinet models that have allow CFM rating of 150 or less. In other words, they don't move a lot of air. Expect to pay at least $200 because, as the saying goes, you get what you pay for.

Non-vented  and recirculating models are just going to stir up the grease and smoke from cooking without getting rid of it. The only advantage of a non-vented hood is the low price.   So, if your kitchen does not already have existing ducting you should seriously consider getting a contractor to install it. With the ducting installed you will be able to purchase a hood that will be effective in clearing away greasy air, smoke and odors.   Non-vented units should NEVER be used with high BTU equipment such as professional ranges.

Microwave ovens that do double duty over your stove have fans and can be vented outside. However, they aren't as effective as regular hoods because they don't reach far enough over your stove. As a result, very little of the smoke and heat from cooking will be captured. The biggest advantage of these models are their space-saving features -- but similar to non-vented units, these models should NEVER be used over professional type ranges and cooktops because of their lower output.

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