Kitchen Exhaust Fan

Your 1st picture in the article covered several lines of text. Let me know if this is my fault (screen resolution, etc) or just an editing mistake. You mentioned the need to provide replacement air. Please elaborate on proper size, placement, and locations. How do you keep cold outside air from filling your kitchen to replace the exhausted air?

Thank You

Tim, I see 2 major problems with your answer to this lady's question:

1. Range hoods should be sized to the range, not to the kitchen. There is absolutely no need for any residential range to require 1000 CFM. About 150 CFM is adequate.

2. There is no such thing as a passive air inlet that admits 1000 CFM. There isn't even one that admits 150 CFM. If you want to prevent backdrafting, you must open a window.

Tim/Charles; there are problems with both of your approaches to the kitchen exhaust fan:

1. The exhaust should be designed with the intent as a commercial kitchen exhaust system.
2. Although low cfm will exhaust vapors, the real culprit and fire hazard is grease. That is why the velocity should be high. Generally, something in the vicinity of 1,500cfm is ideal, This has the effect of scrubbing the grease off the walls of the duct. Unfortunately, this "air scrubbing" isn't quite enough, but; it helps.
3. As much as possible, the duct should be seamless, preferrably welded so it is watertight at all joints. Remember, build it as if to expect a fire. Also, install it with the same clearances and protection from combustibles as for a red hot wood burning stove going through your walls, floors, roof, etc.
4. Make-up air works well passively if a separate air supply duct introduces the air at the hood-air boundary. This allows the exhaust fan to pull the air into the exhaust stream while minimizing the amount of heating or cooling energy loss...it's more energy efficient.

Hi

My question is I want to install a small range under my window in my basement suite. Do I need to have a exhaust fan and if so can I install one as part of my ceiling which is about 48" above the stove?

tom

hello im working as a hvac designer here in dubai..since i only been 6 months in my company i dont have enough experience..i want to ask how to cumpute the exhaust needed for a kithen and how to compute makeup air needed for residential kitchen

Ok...that's twice. Hit wrong key with a splinted finger in the middle of my mssg and caused both to send and can't retrieve either...I give up.

Maybe in a day or so I'll try again. Sorry for the false start(s) and appologizre to anyone eager to answer if they only had the entire question..basically NEED to use downdraft exaust and need some help/ House is 70yr old sngl story cottage with crawl space and raised deck attached to outside wall. Stove is 4 burner gas. Kitchen dims are approx 10x15 open to 10x12 DR and partially open to 20X25 LR through full wet bar. Can't go straight up or up and out.\]

What's my solution ?? Thanks in advance.

Grey G

Hello,

We are currently having our kitchen renovated and the tradespeople want to use an existing roof vent for the kitchen fan exaust fan vent. Should this be done. How will the attic of the kitchen be vented? Please advise.

Many thanks

I want to install an exhaust fan in a small office to vent cigarette smoke. There is currently a small exhaust fan (like in a bathroom), but it is not adequate at all! The room is 11 x 14 feet and the present hole in the ceiling is 10 x 10 inches. It is a 2nd floor room and the fan currently vent through the attic to the outside.

Any advice is greatly appreciated.

Hi Tim,

Read your article again about exhaust fan sizing and ducting the vapors outdoors. Your suggestions are definitely a good idea. As I said before, it's getting the velocity in the duct up high enough that does the most good. There are formulas that will give the proper size duct related to hood size related to the correct velocity that will give the correct cfm so that the correct fan can be selected.

Maybe I didn't read close enough the first time because I see you had an HVAC contractor put foil tape around your duct seams. I've seen this before and it is a mistake. The foil tape used for HVAC applications is not suitable for a grease exhaust system application...a misapplication. That metal foil tape is aluminum which burns at about the same temperature as cardboard. If you can't or don't want to weld the seams in a continuous watertight welded joint, I would at least suggest assembling the joint with high temperature fire-rated sealant slip the joint together and secure with sheet metal screws or steel pop-rivets. Then apply another coat of the high temperature fire rated sealant over that. When grease is hot enough to burn, it runs through everything like water and igniting everthing it comes in contact with. By the way the duct should be made of either 18 ga stainless or 16 gauge sheet metal, not the 24 gauge vent pipe stock. Also, regular cleaning (say monthly) will prevent a lot of the potential for a grease fire.

I would like an exhaust fan that is quiet. Would an in-line fan work.

Any disadvatage to an in-line system.

We are about to start a kitchen remodel. My current cooktop is a GE electric modular with downdraft. We would like to switch to gas. Can we use current downdraft vent system and convert it to a hood, connecting ducts behind the wall? What would be the best thing to do, really hate the thought of ductless hoods.

i have a commercial stove with the related exhaust fan in my home. it is about 20yrs old and the duct to the exhaust has significant grease buildup and doesnt close when the fan is off despite the spirngs that are there. it needs cleaning. can any degreaser work? is there any tips on fixing this easily?

My air conditioning unit used to sit on my deck, until I had it torn down recently and replaced with a screen porch.

The AC unit now sits in a corner on the porch. I'm worried that when summer comes, the warm air from the unit will rise up and collect in the roof.

Of course, it would be nice to move the unit off the porch, but I have no back yard, so there's nowhere else for it to go.

My plan is to have an exhaust fan installed on the screen wall to vent the warm air out of the screened-in enclosure.

My question: can I use a kitchen exhaust fan outside? My kitchen exhaust fan has one side in my kitchen and one side outside. SO I'm assuming that I can get a kitchen exhaust fan and install it on the wall of my screen porch.

Could you recommend a kitchen exhaust fan that is both quiet and suitable for use on a screen porch?

Thank you,

Betsy Lordan

Our house is approx 5 years old. I do not think the builder vented the kitchen exhaust to the outside but instead to a deadspace above an outdoor porch (that is covered by the back roof) Is this exceptable?

I own a condo in an older building which has been renovated but the building never had ducting for exhaust fans (hood fan or bathroom fans.)

Can I remedy the lack of a range hood fan with a ductless, over range microwave and fan? Are there any particular brands that are better than others? What should I be looking for?

Thanks! Mike.

hello Sir,
I have a kitchen exhaust fan Model Number is NVF100p , we didnt had any exhaust fan before , but after that we put a pull type exhaust fan simce 1 year-at present we have a small kitchen exhaust fan Model Number is NVF100P. and since 1 year we have changed more than 3 fan i dont know why , and we changed all the wiring and all and also checked everything but as it is in kitchen , fan gets oily and doesnt work after 1 month- means fan and all body gets sticky like oil and humidity. we use to buy every fan from B&Q or Homebase but i think they dont keep a good kitchen exhaust fan, so can you please let me know , where to buy the good one from where and which one to use for better result and long lasting, as old ones doesnt works and sucks smoke and doent works as we thought , so please advice a good and better one please.
Thanks

Like Darroh, I have a very old exhaust, I think there is grease build up, how do I remedy this? I've cleaned the exhaust filter, but still, when I bake, grease drips from the exhaust onto the stove, and my kitchen walls and surfaces do get grease film. How do I deal with this? What type of help might I need? any comments will be appreciated.

I already have a hood that was particularly custom designed for my kitchen. I just want to buy an effective strong, quiet fan. Do you have any reccomendation for one?
Is there any material/book etc.. that I can read about designing/installing kitchen exhaust fan system and how to builds the exhaust duct/ make-up air etc..
Thank you for any input

We had a whole kitchen remodel done almost 2 years ago.. nightmare! We have a professional range with a grill and believe we have the proper exhaust fan (it works well). The problem we have is backdraft. We get a major draft from the range area and wonder if there is anything we can do or is it possible installation was not done correctly?

I have a high performance range hood named "Kitchen Doctor" it has 2 independent motors with squirrel cage type fans. Am looking for a few small clips that hold the trim pieces on to keep hands out of the fans. Any idea who the manufacturer might be and where I might get parts. This baby will suck the air right out of ya...
Thanks for any info

Because most developer/builders are trying to save every penny they can it seems that most new homes lack proper exhaust, I own such a home. We cook a lot, our kitchen is used not just a pretty room that is only used to microwave something. Our stove top is against an interior wall with another floor above it, I have a basement below us, should we just go down and out?

Hi sir i have a small cafe how can clean my kitchen fan exhaust ducting myself ?

When it is windy outside, the damper in my range hood keeps flapping - and it is really noisy. Why does it do this?

Re Kitchen Doctor fan, I am looking for the small parts that hold the safety meshes in place - just like another reader! Has there been a response to this?

I am installing an exaust hood.
quetion:
My main problem is food odor around my House...this fumes go straight to the second floor..and they become kind of nasty after a while...cloth smells like food....a real problem...
should I install a hood or ...shoul I try something else???/

I have a country kitchen in Tuscany. Normaly the hood is open with an exit hole near the ceiling to the outside and that's it!
I have an exit hole which is lower, about 3feet above the stove. Can I attach an exhaust motor to the inside of the hood, connecting it to a flexible pipe that goes to the hole? I need to adapt the exhaust fan keeping the integrity of the Tuscan country kitchen. thanks for your help

Please save my marriage! We purchased a new gas slide in range and just installed the gas line (not an easy job). Since we used electric before we were not aware that we need an exhaust fan. Problem is the range is on an inside wall and there is a floor above. Please help!

Hi Tim

My husband and I are trying to replace our microwave with a range hood, because the microwave only recycles the air back into the house it does not go anyway. We want to know how to install a range hood so it can vent the smael out of the home. Please help

Can the range exaust be run through an existing chimney where there is am enclosed metal exaust from a gas fireplace? Are there safety or code
requirements in this situation?

Hi Tim,

We're buying a new house that has external venting for a kitchen exhaust fan. My wife likes to cook Chinese traditional foods. In our previous house we had a good exhaust fan. I see here that you recommend a 1000+ CFM fan for greasy foods. The under cabinet mounting is for a regular sized over stove fan. Where can we find a 1000 - 1500 CFM exhaust fan that will fit in that kind of space?

Thanks,

Anyone have any details on the size of a make up air vent for various cfm specifications. Where do you put the vent and how big does it have to be. Can you close it off in a northern climate when its not being used.?

Tim, My wife and I just bought a new and very expensive spec. home. We have been in a month and just now discovered the builder did not vent the kitchen exhaust. It looks like a vent but it makes a 90 degree turn in the cabinet over the gas cook top and vents out the side of the cabinet right back into the kitchen/greatroom and stinks. Was this code and what does the builder or what do we need to do? Help in a smokie "new" house. Thanks

The builder of our new house vented the hood above our gas stove back into the great room. What can he or we need to do to fix & vent to the attic or outside?

Hi Tim,
We are in the middle of a kitchen renovation. The cabinets and design are ordered. We have gutted the kitchen to find that there is ductwork taking up the entire space where the new range hood is going and we will not be able to duct out the range hood. It is able to be recycled but we are now considering putting an exhaust fan (old fashioned styled) in the exterior wall to help with the heat and grease. It will be approximately 7 feet from the new range hood. Is it going to be worth doing? I can live with the "look" of the fan in the wall if it will work to pull the heat out of the kitchen while cooking. But will it? This is the kind of fan we had when I was growing up and it will be placed between the wall cabinets and base cabinets on the exterior wall. Will I be glad I did this or will it be a waste of time and money? Not to mention a new hole in the wall....
Thanks,
Kathryn

I was under the impression that venting the exhaust through the wall was a preferable way to get rid of the unwanted vapours.

Is this a good way o route your exhaust fan?

I have a microwave vent fan. I want to change to exhaust fan. I’m looking for the best solution to make my kitchen look good because the wall of microwave vent fan is the master bedroom. About 7 feet from microwave vent fan is the kitchen door. Above the kitchen is a bedroom of second floor. About 1 foot space is between the kitchen ceiling and cabinets. Do you have any experience remodel this type of kitchen? Do you have any picture that I can get some idea?

We have recently bought our first house. Now the problem is there is no exhaust fan above the cooker. What are the options ,if we not able to install exhaust fan above the cooker as it is in middle of kitchen(kind of)
thanx

Hi Tim, I am having problems with condensation running down my vent pipe, to my island rangehood exhaust fan. I live in Wisconsin this happens when it gets cold, how can I prevent this from happening? My layout is a 6" pipe straight shot up through my flat roof, exhaust fan has damper. Any suggestions?

Hi Tim. Do you recommend self-venting over the range microwave oven's or should the built in ventilation from the microwave oven be connected to the exising vent going through the roof?

I have a Universal gas bar b que grill in my kitchen that is forty years old with an exhaust fan and hood. It produces alot of smoke. Since I am updating my kitchen, it would be nice to get a new hood and I need a strong exhaust fan. What kind would you suggest and where can I buy it? Please let me know as soon as possible, as they are wrecking my kitchen in just a few days. Thanks in advance.

We had a new vent installed when our kitchen was remodeled a year ago.

There is a significant air draft coming down, significant enought that it makes the granite and stove top extremely cold. (Minnesota) The pipe goes through the garage attic and through the roof. What is a sollution to eliminating the draft ?

Thanks

Excellent article thanks Tim.
One thing I notice is that kitchen fans are often not used by 'chef' due to the noise, especially when on higher speeds. Are there in-line fans for kitchens, along the lines of the one detailed in your bathroom exhaust fan article?
Any other ideas on reducing noise?

vent fan for cigarette smoke before it spreads into 3 story building?

As an HVAC professional, I certainly agree that the kitchen exhaust should be sized based on range area and not the kitchen area. Capture velocities of 100-125 FPM are required. For a range that is 36x24 (6 SF), exhaust fan should be between 600-750 cfm.

I do not agree that to move grease, velocity should be increased. Instead, a majority of the grease should be captured before it hits the fan with grease capture grille, as the author suggests. The grilles should be cleaned regularly based on usage.

Ducts seams need to be sealed with sealent to prevent high temperature air from escaping, especially downstream of the exhaust fan, since it is positively pressurized. Duct material should be 316SS or black iron, and slope towards the range so any grease in the duct trickles down into the grille where it can be captured and disposed off.

How do you wire 2 exhaust fans each a black wire and white wire to an single pole double switch? The breaker is a 20 amp.The kitchen exhaust fan is about 6 feet away from breaker.The gable fan is about 20 feet away from breaker .What kind of wire can be used with the breaker and fans?One fan is 1.5 amps and the other fan is 5 amps.

You articles are the best ever.
I want to use an existing stovetop hood to exhaust through the existing port through the cabinets. The problem is that the port is wood and after looking in the attic it seems to dump straight up into the attic with the vents height extending to that of the rafters only. I know that it should be lined with a stainless steel vent. Should it run straight up to an exhaust vent through the roof only? Or can it be be vented some other manner?

I have a 8 inch vent line from my micro wave fan to the roof vent. The roof vent does not have a flapper valve to stop reverse air flow. Does a micro wave fan create pressure to open a valve? Can I create more pressure by necking the line down to 6 inches at the vent?

I was looking at the down vent option for our cooktop and the builder insist that it would take up space and eliminate any options to have drawer space under the cooktop. I know that it would be limited but are there designs that show drawers using a down vent?
Thanks

Sal - Don't use a standard residential inline fan for hood exhaust. If you want to reduce noise in the kitchen, move the fan from the hood to where the fumes are exhausted - either roof or wall-mounted. The fan may be a bit bigger and more expensive, but you won't get the noise.

Gene - you're comments are definately right on. I would just caution against everyone against trying to utilize commercial practices in residential applications. Keep in mind most people are only using their exhaust fans once a day for 30 minutes at the most, and utilizing residential fans that won't have the horsepower required to overcome the static pressure required to exhaust air at 1500 FPM, so grease entrainment will be fairly minimal and most of the grease that is entrained should be caught at the filter in the hood.

The safest, easiest, and cheapest way to ensure proper kitchen exhaust opperation will always be to minimize the length of the ductwork and any and all transitions and turns - just get it out of the house as quickly and easilly as you can.