Home Kitchen Exhaust System – Range hoods dress up the kitchen, but their function is underappreciated. In a tight building, a high-performance range hood is critical to indoor air quality. Why don’t customers turn it on? Kitchen range hoods, with their stainless-steel skin and high-tech lights, are fashion statements that complete the look of a well-designed cooktop or stove. Oddly enough, many people rarely turn on their hoods and use them for their primary purpose – to expel smoke, fumes and odors from the home. The Vent-A-Hood range hood uses centrifugal blowers, which eliminate the problem of clogged filters. There are reasons. Range hood fans are noisy, or they are supposed to be. Some people don’t think they need to turn it on – just to boil water, or maybe fry an egg. When they hit the switch, it’s not often until the kitchen is covered in fog. Then they switch off the unit as soon as they are done cooking. This behavior contributes to the growing problem. With fewer air changes per hour, homes today are tighter than ever. Add in the popularity of gas stoves, which emit nitrogen dioxide and volatile organic compounds as combustion components, and the stage is set for poor indoor air quality. How poor? A study by the University of Sheffield in England last year found that NO2 levels in urban kitchens with gas stoves were three times higher than outside measurements. Concentrations of airborne particles were also higher than the safe levels set by the government for outdoor air quality. The study complements research findings by Bron-Newton LLC, a leading North American manufacturer of home ventilation products. About half of consumers surveyed said they were concerned about indoor air pollution, but less than 20 percent thought they had a problem in their own homes. “Consumers, in general, don’t really know how poor their air quality is, or how much cooking contributes to the problem,” says Brian Welnitz, marketing manager of kitchen ventilation at Bron. According to John Rose, technical program manager at the Home Ventilating Institute, in some cases, people recognize that they have indoor air quality problems, but mistakenly believe that air filters take care of the problems. “We know from surveys that they are concerned about indoor air quality, but don’t know all of their options,” says Rose. Reducing Volume In recent years, however, range hood manufacturers have begun to bridge this disconnect. One way is to design motors that operate at a whisper, especially at low fan speeds, to quiet the excuse of too-much-noise. Zephyr’s Napoli island hood, for example, features the company’s DCBL noise-suppression technology, with a motor that uses direct current instead of AC. It reduces range hood noise by 77 percent, says Zephyr. Another noise-limiting approach, most popular with large, commercial-style hoods, is to place the blower elsewhere in the home, away from the kitchen, within the ductwork. Either way, customers should look for a low son rating, which is a measure of rudeness. For comparison, a modern refrigerator emits one or two soot while running. The sone level for a range hood varies depending on the fan speed, but two to five sones are common. Of course, fan speed is an important factor. The fan’s performance, measured in cubic feet per minute, must be able to keep the heat generated by the stove or cooktop at its maximum settings. As a rule of thumb, figure one CFM per 100 BTU. And remember that exhaust performance will be greatly affected by the ductwork depending on the length, width and number of turns. Manufacturers have also developed technology that introduces a measured amount of fresh air each time the hood is activated to balance the exhaust flow. It is better to suck in cool, outside air through holes and cracks in the building envelope, which can create conditions for mold growth. Make-up Air Critical Do you have enough make-up air? When the range hood pulls air out of the kitchen, negative pressure is created in the house, a situation that is amplified in a tight house. The solution is to replace the air with fresh air from a controlled source. Make-up air dampers are sized to balance the air pressure in the house, and are wired to operate automatically when the hood is on. In many cases, the damper can be fitted to the home’s furnace duct. The size of the duct will influence the exhaust flow and the number of dampers required. For example, a six-inch round make-up air damper can handle up to 600 CFM. The 8-inch diameter is good for up to 1,000 CFM. You can find sample installation documents here. Check it out. The blower door test can quickly tell you if a controlled fresh air intake is needed in the home to install a range hood. But getting make-up air right can be tricky. Climate, building-air leakage and hood exhaust rate are three obvious factors that contractors need to consider. They then need to account for duct-system losses and building envelope depressurization in calculating design flow rates for hood exhaust. It helps in determining the number and size of make-up air dampers. Dampers, which are usually between six and 10 inches in diameter, can be installed in exterior walls or, in some cases, in the return-air plenum of a home’s furnace or air conditioning ducts. Braun has just introduced an online tool to help contractors determine the right make-up air solution for their projects. The web tool reflects the fact that since 2009, model building codes such as the International Building Code include a requirement for interlocked (automatically activated) make-up air for home range hoods capable of exhausting more than 400 CFM. Most state and local codes are expected to adopt these standards in the coming years. “If you’re running a 600-CFM range hood and your house is really small, you’re going to need more make-up air,” Wellnitz says. “You’re letting the house down faster.” Accounting for make-up air can also eliminate the potential risk with exhaust fan-backdrafting. When the negative pressure created by a fan draws combustion gases from a furnace or gas water heater into a tightly sealed home. It turns out that backdrafting is becoming less of a problem, Rose notes. That’s because most high-efficiency appliances in today’s new homes use direct venting or some other sealed-combustion system and don’t draw their make-up air in. Range Hood Retrofit But the market for new range hoods in existing homes is huge, with around a quarter of the country’s housing stock being 40 years or older. Many older kitchens never had a range hood or any ventilation. If the contractor is lucky, the range is on the outside wall. If there is no cabinet above the stove, a wall-mounted chimney is a good solution. Another idea is to build a soffit to hide the duct running on the outside wall. “The simpler ones are in ranch homes where you can go right into the roof cap in the attic,” says Welnitz. There are options for a two-story home with an interior wall, using a soffit, opening the roof or going in and out of the basement that will require some “remodeling,” Wellnitz says. Most range hood manufacturers also offer the option of recirculating the exhaust air through a filter. It’s a poor choice that does little to improve air quality, but in some apartments and condominiums, there may be no access to an exterior wall. But the big problem now seems to be how to educate people about the need to use a range hood whenever they cook. Quieter motors can help, but as homes get tighter, it’s possible some day that range hoods will be interconnected with stoves and cooktops, just as bath fans are connected to light switches in many commercial and some residential buildings. have “In the future,” says Rose, “you’ll see range hoods that operate completely independently of the user. They’ll use sensors that will determine what’s happening on the cooktop and then act at the appropriate level. At Braun, Wellnitz notes that Some range hoods already have a sensor that turns on the exhaust if the cooktop is run at maximum output, so the heat doesn’t destroy the hood. “We have to giv
e the customer the ability to override that feature,” he says. “But what happened to the cooktop? The technologies are already there to understand what is happening and to operate the hood in the most efficient way to remove pollutants and odors.”
By Alan Naditz Alan Naditz is the managing editor of Green Builder magazine. He has covered numerous industries in his extensive career, including residential and commercial construction, small and corporate business, real estate and sustainability.
Home Kitchen Exhaust System
ESG is a new concept to many. Here are some talking points that help explain what ESG is all about…When you cook, your gas stove (and your soon-to-be dinner) sends heat, odors, and moisture into the air. Enter the kitchen
Time To Vent: Why You Need To Turn On The Kitchen Exhaust Fan
Kitchen exhaust fan system, kitchen exhaust system for home, home depot kitchen exhaust fan, restaurant kitchen exhaust system, kitchen exhaust hood system, exhaust system for kitchen, mobile home kitchen exhaust fan, kitchen exhaust ventilation system, home depot kitchen exhaust hood, kitchen exhaust system cleaning, home depot kitchen exhaust fans, best kitchen exhaust system