Range Hoods - conflicting advice! What to consider?

12 years ago

Hi - I am remodeling my kitchen, and have selected the Wolf 48' dual fuel range with a grill and griddle. I'm getting different advice re: the range hood from my architect, appliance rep, general contractor and home building friend. I need help!

My husband is 6'3' so we want to mount the hood at 36" instead of standard 30". The hood will vent directly up and out the roof thru 10" duct.

Our kitchen, living room and dining room are now all one big "great room" so noise and smell issues are real.

The appliance rep recommended VentAHood 48x18x27 b/c it is "quieter and more efficient". She blew off all other brands, so I'm wondering if maybe she gets better compensation from VAH? Our builder friend recommends Wolf Pro "Low Profile Wall Hood" or the "24 Deep Wall Hood".

They are all expensive, but I'm realizing how critical they are to the house.

What else do I need to consider? Any personal experiences -- do you love or hate the one you have? THANK YOU for any and all advice.

Featured Answer

aprince

12 years ago

The reason you are getting conflicting advice is because of your 10" duct.

Your builder recommends the Wolf line because the 1200 CFM and 1500 CFM blowers connect to 10" duct. However, this will be noisier than the Vent-A-Hood when connected to 10" duct. Therefore; your salesperson, who appears to have been listening to you, is aware of the noise factor in your situation and recommends a 900 CFM hood. Vent-A-Hoods are very quiet but 900 CFM is not enough to ventilate a range with a griddle and a grill.

They'll both perform okay, but you may not like the noise from the Wolf and probably won't like the power of the Vent-A-Hood.

Your situation requires adequate ventilation and quietness. A different Vent-A-Hood, with a 1200 CFM rating instead of 900, would do both, but you will need to change out to a 12 inch duct. The size of the duct is a determining factor in overall noise of a hood. Larger is always quieter and the extra 2 inches decreases noise by about 30%.
Your builder does not want to redo this and the salesperson is selling to what is already there.

There could be an X factor. The Vent-A-Hood, although you won't have to clean it often, requires you to reach up into the shell and detached the box around the motors for cleaning. Not knowing your health or what you look like I don't know if this is practical or not. Your builder may know this and recommends the Wolf for that reason. But, your 6-3 husband can certainly do this task then.

IMO, when comparing these two lines, go with a 1200 CFM Vent-A-Hood, utilizing 12 inch duct.

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Comments (14)

francoise47
12 years ago
First, mounting the hood at 36" is not going to be a problem if you have sufficient CFMs.
The specs for our Best hood said it could be mounted anywhere between 30 and 36" off the range top.
30" is not the only standard.
A powerful hood mounted up to 36" above the range will work very well.

Second, both VentaHood and Wolf make very good hoods.

But, the new Wolf Low Profile hood you are considering,
although a sharp looking vent hood,
is not ideal for a big 48" wide range with grill and griddle.
The flat low profile shape does not provide enough capture area for the rising smoke and grease.
If you want a Wolf hood, you should be looking
at the Wolf Pro Chimney hood or Pro Wall hood
(depending on the look you want.)

See the pro hoods at this link:
http://www.subzero-wolf.com/oven/range-hood/chimney-hood

Your vent hood for a powerful range should ideally be 6" wider than your range.
This means you should be considering vent hoods that at 54" wide.

If you plan to use your griddle and grill to any extent,
consider the 27" deep version of the Wolf vent hood.
24" deep would be the minimum depth.
Don't consider the 22" depth at all because it won't cover your front burners.

All of the above general advice about dimensions also applies to the VentaHood.

You'll also have to make a decision about what kind of blower to get -- internal, inline, or remote.
You can read all about ventilation at this link:

http://www.subzero-wolf.com/resources/products/downloads/WolfVentilationGuide.pdf

Here is a link that might be useful: Wolf Low Profile hood
markb
12 years ago
Hoods can be mounted at any height you wish provided that certain criteria are met. The higher the hood, the higher the cfm exhaust requirement and the greater the capture area.

My hood is mounted 43 inches above the range and allows a four inch clearance above my 6'2" head. To allow my hood to be effective, the exhaust rate is 2000 cfm and the hood depth is 37 inches.(37 inches is NOT a typo)

Cooking effluent expands as it rises.(think cone shape) The higher hood needs a likewise greater depth and length or a portion of the smoke and/or grease will escape the hood entirely.

Because I wanted my hood at a height that is rather uncommon in a residential setting, I had my hood fabricated and installed by a commercial HVAC company. It was rather pricey but a wise investment nonetheless.
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OK, lets go at it piecemeal. What is the width of the range? Is it electric coil, gas, or induction? If installed, or if there is a fixed installation plan, what is the spacing of the upper cabinets on the sides of the range? With respect to air flow: There are several commonly used rules of thumb, one of which is based on total potential BTUs. The BTU method is an indirect method of estimation of needed flow rate, and doesn't account for how well the hood overlaps the range. I prefer the more physical approach based on the needs of capture and containment (what hoods are supposed to do). Capture efficiency depend on how well the hood aperture overlaps the rising and expanding cooking plume (effluent). Containment efficiency is determined by how well the hood air flow through its baffles (or mesh filters) keeps the plume from reflecting out of the hood when it hits the sheet metal baffles or mesh structures. A generally sufficient air velocity is 90 ft/min for gas cooking; induction cooking may allow one to get away with a bit less as it doesn't have a gas combustion plume adding velocity to the cooking plume. Electric coil plume velocities may be in between; the lab measurements that I've seen published don't include coil cooking measurements. (Gas cooking can cause the central part of the rising plume to reach 1.2 m/s.) The necessary air velocity has to exist over the entire hood aperture; we don't get to block off portions of the aperture that we are not cooking under. The aperture has some area -- more if there is good overlap of the plume expansion. Hence I suggest 90 CFM/square foot of aperture to get 90 ft/min everywhere. (You may notice that this is about half of the uprising velocity. We don't need to equal it, only keep it from reversing while the baffle aerodynamics take control of it. Baffle design and mesh flow effects may vary how well a given average air velocity works. I know that around 90 ft/min works for me when induction wok cooking, and that Greenheck suggests for similar cooking a value of 85 ft/min for their commercial hoods. There are types of commercial cooking that call for considerably more velocity, such as grilling, but this is not in the scope of our present discussion.) Ideally, to get good capture to make use of this containment, the hood has to overlap the locus of hot pan bases by about 10 degrees half angle. From this another rule of thumb has arisen that suggests overlapping the cooktop by 3 inches on the sides and front. This overlap is probably too optimistic for some searing or wokking, but many here have reported good capture with this size. For a 30-inch range, this would require a 36-inch wide by 27-inch deep hood. You may not have room for this, or you may wish to depend on the side cabinets to channel the effluent from rear burners and cook the greasiest stuff there. So for a 30-inch range, the minimum hood would probably be 30 inches wide by 24 inches deep (front to back). I suspect for most 20 inches deep is too short. As you may appreciate, the larger hood thus has higher total air flow requirements than the smaller hood, costs more, and requires more make-up air. So you may also appreciate that this aspect of performance alone is in conflict with affordability for a given level of aesthetic design. Wait until we get into make-up air issues. kas
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The OP wrote: "So...I’d love the size of a larger range and a larger hood just for “style”..." Few want a larger hood for style; most resist having a larger hood even though it increases effectiveness at the cost of more required air flow rate and potentially a deliberate means of supplying make-up air. Cooking plumes expand as they rise, hence the hood capture aperture has to be larger than the area occupied by whatever pans might be used on the cooking surface. Otherwise, the effluent partially spreads into the kitchen allowing grease and moisture to settle on surfaces, and odor to spread and linger. A six-inch wider hood helps achieve this. A large enough front-to-back dimension is also needed. Assume the plumes expand at an angle of about 10 degrees from the vertical. The hot cooking plumes will have an upward velocity that depends on cooking surface temperatures and presence or not of gas combustion products. When these plumes (to the extent that they are captured by a large enough hood) reach the hood filter, they will bounce off due to conservation of momentum unless the air velocity induced at the filter by the hood blower is high enough. Commercial and residential practice suggest a value of 90 ft/min at the hood entry aperture (not the filter) is sufficient to retain the effluent and achieve containment. 90 ft/min is equivalent to 90 CFM per square foot of hood entry aperture. Use of induction cooking without any searing or wokking or hot frying may allow a lower value, but not below 60 ft/min. Hood blowers can only meet their specified zero pressure loss flow rate when hanging in free air. All other configurations have pressure loss (air flow resistance) as a function of flow rate, and thus when installed each blower flows less than its rated value. Buying a blower rated around 1.5 times that needed for containment (see above) should overcome the likely pressure losses, assuming there is a make-up air path suitable for the flow rate.
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Unless you already have make-up air from the previous ventilated hood installation, I'd go for 390 cfm (cubic feet per minute), which is below the limit for MU air safety code requirement in most areas--but check with your local code. Since you have an electric range, and it appears to be venting directly to the exterior, that should be sufficient. If you post the questions to the Appliance forum, there a several very helpful posters who can answer specifics.
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kaseki
12 years ago
Congratulations, markb, on applying the concepts of capture and containment to a non-standard configuration!

Perhaps you should mention how you obtain make-up air, as it is unclear whether tredog is aware of the need.

kas
djg1
12 years ago
We did 34.5" high on a full-depth tented hood, with baffles (1100 cfm, 10" duct straight up through the attic and roof) -- that was within spec for both the hood and range and it works great.
billy_g
12 years ago
We just put in a hood for a high power 48" cooktop. Definitely go 54 inches wide. We went 27 inches deep and if we had it to do again we would go 30 inches deep because the front of the hood doesn't get in the way.

For the least noise put a big fan on the roof. Abakka makes a great 1400 CFM fan that we used. There is nothing magical about Vent-A-Hood and I doubt you want to reach up there and clean those squirrel cage things.

You can even put in a muffler if you have room in the attic.

Billy
tredog
Original Author
12 years ago
You are all amazing and thank you for the helpful responses. I never knew range hoods were so complicated. Thank you for taking the time to help me. I really appreciate it.... especially aprince's advice about having my husband clean the hood!
davidro1
12 years ago
tredog the big thing is capture and containment. This has been mentioned.

A few stray remarks here and there have mentioned other important things.
1 is MUA, the incoming air you need to fill the house when your powerful fan sucks air out of the house, and the 2nd is the benefits of a remote fan blower motor (inline in the ducting in the attic or external attached to the outside of the house.) If you don't know about MUA you haven't got anything yet. If you only look at fan blowers that are installed in the kitchen right in front of your ears you really haven't looked at the whole range of options yet.
tredog
Original Author
12 years ago
Hi davidrol... so, i have a feeling this will be an incredibly naive comment... but I was just planning to open a window for the make up air?? I've been thinking about a 1200 or 1500 remote CFM roof mounted blower (i can also increase vent to 12"). Do I need a separate appliance for the MUA? Thanks.
User
12 years ago
Your local building codes office will regulate how complex the make up air will need to be. If you live in a mild climate with little heating or cooling, and you also have little building regulations, then MUA may be as simple as opening a window when you cook. That is an unlikely situation though. You are more likely to need a dedicated duct for the MUA, and if you live in a cold climate, you will need a Heat Recovery Vent system in order to not freeze your home to death by sucking out all of the warm air and replacing it with cold. That can run into several thousands right there. Your best bet it to consult a HVAC professional to deal with the whole ventilation issue.

If you have other gas fired elements in your home, correct MUA is a critical life threatening issue.
markb
12 years ago
Thanks kas for mentioning make-up air as I neglected to address that in my previous post.

As was discussed previously, I utilized a commercial HVAC company to fabricate and install my hood as my requirements were somewhat nonstandard. This company was recommended to me by a local restaurant supplier from whom I purchased a commercial gas range and char-broiler. I was aware that I would need make-up air but was unsure how best to accomplish this. At their invitation, I went to a local Applebees's that was under construction to view the ventilation systems said company was installing. It turned out to be the perfect solution for my home.

My hood was fabricated to deliver make-up air from the inside front of the hood. It blows air directly to the baffles in the rear and is, along with the cooking effluent, exhausted outside.

The hood exhausts 2000 cfm, make-up air brings in 1600 cfm which results in a meager 400 cfm draw from my living space. The real advantage of a hood of this type is that make-up air does not have to be heated or cooled; a real energy and money saver.

As I said previously, a system like this is a bit pricey. Mine was installed about thirteen years ago. The hood, roof mounted blower, roof mounted make-up air unit,all electrical and complete install was about $8000.

It was worth every penny.
davidro1
12 years ago
markb I'm glad to find out about someone who has make-up air delivered to the point of need without any air handling.

tredog i'll guess that in your climate you can open windows.
kaseki
12 years ago
Markb:

It seems your ventilation company came up with a good design. I've seen at least one paper that reported a study result based on Schlieren photography indicating that the proximity (and direction, I'm sure) of the MUA flow disrupted containment (in that particular hood).

Please let us see a photo of the hood guts, if you have a chance.

kas
markb
12 years ago
kas,

I have no doubt that proximity and direction of make-up air can interfere with effluent containment regardless of hood design. Something as rudimentary as an open window opposite the hood can cause cooking vapors to escape the sides of said hood.

In order to eliminate that possibility in my configuration, the hood (along with the range and char-broiler) was installed in an alcove with each end of the hood making contact with the corresponding wall.

Range Hoods - conflicting advice! What to consider?

aprince

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