Realistically, it seems like you would have to go 36" above the cooking surface to avoid serious annoyance to a 6'2" chef. And that would add to noise and undermine the effectiveness of the hood because the "rising effluent" spreads as it rises.

So I have read in other threads that rising effluent spreads at an angle of 22.5 deg from the edge of the cooking pan. That would mean that even a 27" deep hood mounted 36" above the cooking surface would fail to capture a lot of the effluent:

So, based on recommendations that I have read about here on GardenWeb, in order to
1. prevent head bumping and provide for visibility for a 6'2" chef and
2. provide appropriate capture area for cooking effluents rising at an angle of 22.5 deg
...I would need a 36" DEEP hood mounted 38" high from the cooking surface.

Does anyone do this?? Or am I missing something? That is an awfully big structure.

feisty68, here is a wild thought --

How about moving the two 22K BTU burners to the back in your RNB configuration, so the smoke generated from the back burners is more likely to be captured by a standard depth hood (24" or 27")? Given that you and your husband are both tall, I imagine you won't have trouble frying or searing things on the back burner(s)?

I also saw that you asked the following question in a different thread:

``I am having trouble finding hoods with concave bottoms. Most of them have flat bottoms."

I want to mention that BlueStar and Prizer hoods do have a pyramid-shaped bottom, but I cannot speak to their noise level. Below are a couple pictures to illustrate what I mean.

Also, if you are going to consider putting in the larger duct (8"), you might as well consider 10", which is the duct size recommended to me by an appliance store owner for 1200cfm internal blower. I think he is way more knowledgeable than an average sales person.

BlueStar:

Prizer:

This post was edited by ILoveCookie on Wed, Mar 26, 14 at 15:44

Thanks for your suggestions ILoveCookie!

I'm actually 5'5" and my husband is 6'2". I think having the hot burner at the back would be a problem for me as it's not a comfortable reach for the stirring, etc. required for a complicated dish.

Good to know that BlueStar and Prizer hoods have pyramid-shaped bottoms! I will have to further research the noise levels. Those hoods certainly do look good!

I'm not sure what is involved with increasing the duct size on an external load-bearing wall with a special building envelope rainscreen. The studs are probably 12" on center so I assume a 10" duct is not feasible and I don't want to get into structural issues.

feisty68, for some reason I thought 5'5" is quite tall... probably because I am barely 5'2". :)

The studs in my current (and previous) houses are 16" on center. Even if they were 12" on center, I think a good GC or carpenter could find a way to compensate for one possibly lost stud, like adding some horizontal studs or boards or something like that, to distribute the load. The waterproofing shouldn't be too difficult either.

Just to give you some idea... it may not be as scary as you thought. :)

This post was edited by ILoveCookie on Wed, Mar 26, 14 at 16:17

So, looking at the option of a 36" deep hood that is 38" above cooking surface...

Would I use a hood insert like the one linked to below? It is only 19" deep so it would need shroud that would build out the bottom area to 36" deep and have a concave pyramidal bottom. I would only have about 18" clearance from the ceiling to the bottom of the hood.

Here is a link that might be useful: Kobe Built-In IN-026-700

ILoveCookie, load-bearing walls definitely have studs that are 12" on centre in my building (4 storey multifamily complex) - I know for sure based on experience and looking at the engineering drawings. I don't want to tinker with the studs because it would require a building permit...a Pandora's box that we are already dealing with because of structural issues related to converting a small load-bearing wall to column(s).

This post was edited by feisty68 on Wed, Mar 26, 14 at 16:22

I understand the permit process can be a huge pain. I am going to be dealing with it soon...

OK, here are the dimensions of my preferred hood Kobe CH9136SQB-1:

The drawing below represents my custom solution. The orange part would be framed with 2x4s and provide a way to mount the hood at the desired height of 38" above the cooking surface. The hood + soffit together would extend 36" from the wall. Although only the forward 22" of that depth would be the hood itself, most of the smoke is created by the front two burners so this set-up should capture most of the cooking vapours.

The effluent angle varies also with different cooking so the "Finnish" papers I reference at my Clippings should be consulted for the variation. Note that these angles are without any effects of the hood. The hood can't do much down at the cooking surface, but if the air flow rate is high enough at the hood, there will be some modest curvature of the effluent paths as they approach the hood, bending the effluent toward the hood center, thereby modestly reducing the effective angle in the direction of the nearest hood aperture edge. Also, perfect capture may be difficult when depending on residential hoods, so some effluent escape can occur, and sackcloth and ashes are probably not called for in such a case.

My hood has to overlap both a 36 inch induction cooktop and a nearby 3500W Cooktek induction wok hob. At full fan power (probably 900 cfm from a 1500 cfm rated blower) the wok effluent is pretty well captured, even though the wok edge is only a few inches in from the hood aperture left-hand edge (not at home right now to measure this) and the hood is 34 inches above the counter. I attribute this to a combination of the smallish zone where the wok hob actually heats the wok, the actual expansion half-angle for this cooking being more like 10 degrees (guess) and the effect of the 900 cfm gathering air from around the peninsula such that there has to be a slight inward angle to the least effort air path.

One other comment. I am at least 70 inches tall and the hood base is at 70 inches from the floor. Due to natural bending when reaching into the cooking zone, I clear the hood by at least an inch.

So my recommendation is to choose a slightly lower angle than 22.5 degrees, be sure it is measured from a likely diameter pan bottom and not from the edge of the cooktop or of the counter, and depend on enough air flow to deal with the reduced angle. I'll try to remember to measure the angle that is working with the wok. I think at full power my air flow at the hood aperture is in the ball park of 90 cfm per square foot of aperture.

kas

Thanks again for your input Kas! That is helpful.

I have modified the design as follows:

* hood bottom is still 37" above cooking surface
* the 22" hood is now centered over the front burners depth-wise
* a 7" deep frame backs the hood
* from the actual front pan edge (on front burner) to the edge of the hood, an effluent angle of 10.5 degrees should be captured

Update and correction.

My hood is 35 inches above the counter, and since the hood edge is over my head when standing at the counter, the one-inch of head clearance is better explained. Caution: If you will end up standing under a halogen light, be sure that the replacement LED light will clear your head or that you have a tin-foil hat.

My wok hot zone edge is roughly 6 inches inside the hood aperture at the hood end, which computes to a half-angle of 9.7 degrees. I think you will be OK with 10.5 degrees except perhaps when searing at temperatures higher than achieved when wok cooking. (My induction wok is only equivalent to about 30 kBTU/hr, whereas Chinese restaurant wok gas burners may running in the 100 kBTU/hr playground, so my temps for a given quantity of food may be lower.)

Next issue is the offset at the frame in the back. To keep rising effluent there from reflecting downward and outward when it hits the 7-inch frame, it is desirable that the backspash be angled from the back of the stove to the aperture, preferably over the entire 38 inches of height so the angle is shallow, but shorter angled sections may be used to compromise with aesthetics. An angled backsplash might typically be sheet metal. I've seen diamond embossed stainless steel backsplash photos here, although I don't recall any that were angled.

Alternatively, or in addition, side skirts like commercial hoods often use, particularly when a shelf is above the burners, can keep the reflected effluent (now with low momentum) within the cooking zone long enough for it to become entrained in the other rising effluent and air and be exhausted. Side skirts don't go all the way to the stove, but might want to be around 18 inches for your configuration. Side cabinets may perform this function, but in my view should have metal on the sides exposed to the heat. They will certainly be easier to clean.

kas

Along these lines, I'm replacing a hood and if I use the Kobe hood I'd prefer, it's 9-1/8 in high. With the existing cabinet configuration, that would place the hood at 25" above the range. Kobe recommends 26"-30" above the range. What issues would I have at 25", other than maybe some vision to the back might being blocked?

Kas, thank you very much for your analysis! I will consider an angled back and/or side skirts.

Interestingly, I was above to observe how much 520 CFM "sucks". My old hood is installed adjacent to the new range position, but completely non-overapping (right hand side of hood lines up with left hand side of range). While frying bacon, I was surprised at how much the smoke was deflected towards the hood. Of course, the hood is a below-cabinet mount so that is much lower than I will have.

Willinak - have you checked your range specs? My Bluestar specs require minimum height of hood above cooking surface.

feisty, my range, Capital Precision 30" doesn't show any hood height specs, at least that I can find. The hood, Kobe says 26"-30" above range. I'm a bit less than that, and wondered if that's ok. Should trap more smoke and grease anyway. ;-)

If low noise is important, here are a couple of ideas that I've used to solve the noise issue for my clients.

1.) The dimensions of the range hood have nothing to do with the noise level. In high-quality range hoods (NOT made in China), the noise is created when the air passes through the filters (regardless - baffle or mesh). The dimensions of the duct, in this case, also don't make a difference, as long as it's rigid (not flexible) and not smaller than 6 inches, and properly sealed at the joins.

2.) It has nothing to do with make-up air, since residential type range hoods, especially those designed for 6-inch duct, in most cases, will not require make-up air. There's no such thing as a completely airtight house, and you will have outside air coming in through various sources, such as doorways, window frames, bathroom exhaust ducts, dryer vents, etc.

3.) What really makes the noise is when the air goes through the filters, and the only thing to reduce it is to use a "muffler", which does the same thing as it does in a car - reduces the noise from the engine. The only company that I'm familiar with that makes such mufflers, which they call a "silencer", is an Italian manufacturer Futuro Futuro. They're available in the US, and in my experience, they reduce the noise, I would say, 20-25%. They also offer a remote blower adapter/kit, which in combination with the silencer, makes a significant difference. VAH also offers a remote blower option.

Here is a link that might be useful: Range Hood Silencer

It has nothing to do with make-up air, since residential type range hoods, especially those designed for 6-inch duct, in most cases, will not require make-up air

Many municipalities require makeup air if a hood is capable of 300-400 cfms.

A silencer can only reduce noise generated beyond it (away from the hood). The hood baffle noise (due to air turbulence) and duct noise (due to air turbulence) before the silencer will not be affected. Silencers are most suitable when the blower is mounted on the roof or in-line in the duct beyond the silencer. Most of the noise that the silencer can reduce is higher in frequency, and this noise will be due to blower blade tip turbulence and duct turbulence.

It occurs to me that there can be variations in baffle design such that for some air velocity through them one design can be quieter (lower turbulence) than some other baffle design. One would hope in such a circumstance that the effectiveness of centrifugal collection of grease would not be compromised by the quieter design.

Baffles have to be cost-effective to manufacture (they won't be NACA airfoil shaped), so I would expect that reduction in noise is a trial and error proposition, at least without a big deal computational fluid dynamics project. Quieter hoods (with remote blowers) may be so due to fortuitous design, or a lot of trial and error.

When the blower is in the hood, then the blade tip turbulence noise is likely to dominate the baffle noise. In the case of VAH; where the blower is also the baffle, one gets the combination from a single source.

kas

kaseki and robert_sett....you are both on point, and have posted informed commentary. Thanks!

Robert_sett, thank you for your comments.

Do you have personal experience with installed Chinese-made hoods? IMHO, the fact that something is made in China doesn't automatically mean that it's poor quality - my new sink is a case in point. Also, I wonder if any North American or European brands of range hoods can assert that their products are made 100% in North America/Europe? I know that my new BlueStar range (US Brand), which I'm very happy with, is a United Nations of components - US, Europe, China, etc.

Good point about make-up air being available in non-airtight homes, though that can be an issue in a new-ish apartment like mine. I purposely left a gap under my front door for that reason.

Silencers and remote blowers are also made by Fantech.

In your experience, would a silencer be expected to reduce the noise by 20-25% in my particular configuration?

As discussed earlier in this thread, a remote blower is unlikely to result in lower noise in my particular configuration (remote blower would not be far enough from window/hood).

Thanks for the comments kas...you are my hood guru!

Feisty68, yes, I do have experience (fortunately, in the distant past and "never, ever again") with Fabyka and Euro-Kitchen hoods. You're right, it doesn't "automatically" mean it's bad quality, especially today, when things are made from parts from all over the world. But it's one thing to compare a sink, which is an inert piece of metal, to a complicated mechanism with associated electronics - there's a lot more points of failure there. Plus, the ability of Chinese companies to "get creative" with specifications is simply amazing.

That being said, yes, even some major European appliance manufacturers don't produce all of their components in Europe. However, the quality of materials & components, the assembly process and quality control, and the truthfulness of specifications, such as CFM, noise level, grade of stainless steel, etc - is very different from China/Taiwan/India.

You could do your own test. For instance, take any Chinese range hood which is made from "highest quality stainless steel" (supposedly AISI 304), and stick a magnet to it. If the magnet sticks - the steel is NOT "highest quality", it's simply well-polished combination of cheap iron and just a little bit of nickel (nickel for color only).

However, REAL high-quality stainless steel will never attract a magnet. That means that a significant portion of iron has been replaced by chrome and nickel - that's what makes stainless steel truly stainless.

Did you know that some high-end refrigerator manufacturers actually have to insert a sheet of low-grade steel behind the (high-grade but non-magnetic steel) door panel, so fridge magnets actually stick?

But, let's face it, 99% of consumers don't know this, and moreover, don't care. By the time the cheap stainless steel turns yellow and the seams start to rust, they will be occupied by another project (for instance, replacing the previously purchased Chinese product).

There are many types of corrosion resisting steels (CRES) including the 300 series and 400 series. The 300 series is non-magnetic and tends to resist discoloration. This is the type I would expect on SZ, Perlick, Wolf, and other high-end brand exterior surfaces. The 400 series is magnetic and discolors somewhat more easily from fingerprints and food contact. 400 series CRES might be used for induction cookware lower surfaces, all of which are magnetic.

For a much better treatment of this subject there are many web sources, including Wikipedia [http://en.wikipedia.org/wiki/Stainless_steel]. For relative corrosion resistance, see the link provided.

Here is a link that might be useful: Metal corrosion table

feisty,

Did you make a final choice on your hood? I'm in the same boat, but have a bit of flexibility since we are building a new house. I RARELY turn on my 360 CFM hood because its so load (to me) at ~5 sones. I want a more powerful, and quieter hood. It would be an insert since we are doing a custom hood (made by the cabinet maker).

Sorry I didn't see your reply Nepool - notifications don't seem to be reliable?

I haven't ordered a hood yet. Good luck and let us know what you get.

Nepool, if you're looking for quiet, consider the Insert-Liner hood from Futuro Futuro. It's only 3.2 sones at maximum speed, and you can add the silencer to reduce the noise down to the 2.5-sone neighborhood. They have it in different sizes, here's the most popular one: Futuro 32-inch Insert Hood

Also, if you're putting it into the cabinet / custom enclosure, consider adding some sound insulation to the inside of the cabinet. There are some automotive products that work very well in this application, such as CLD Tiles, GT-Mat, and DEI Boom Mat. Materials that are meant for "underhood sound reduction" or covering the engine compartment / transmission tunnel also have the benefit of being thermally insulating.

Here's a sampler of automotive sound reduction materials:

Eastwood - sound reduction materials

Hey feisty, what hood did you choose?

Our reno has tragically stalled so we don't have a hood yet! My husband had a series of health crises and we are DIYIng a lot. Still hoping to get the Kobe.

Curious to know if there is an alternate to the exhaust fan/hood over the cooktop.

Do pop-up venting systems work? Would a through-the-wall whole room exhaust fan work in this relatively small kitchen?

Hey folks,

I'm resurrecting this thread because I still don't have a hood! Life got in the way and our kitchen is half finished.

I want to revisit what my options are for venting my 30" RNB Bluestar. Some considerations:

• sound level is a huge priority - I know myself...I won't use it if it's loud. I need very quiet settings for stuff like making bacon which I do all the time, but also something powerful enough for searing steak
• venting to the exterior is directly out of the window wall (where there is a walkway)
• an external blower is not an option
• 36" wide hood, possibly just an insert as I'm interested in a DIY surround
• MUA will be open window (no fireplace, furnace, hot water heater, etc. to consider)

Recommendations for brands, models of 36" inserts or hoods? I was looking at Kobe but I'm open to other options.

[If you are a hood salesperson feel free to reply but I will only consider hoods that have readily available information about the CFM and sone level for each setting.]

Any experiences with Futuro Futuro 32" Insert-Liner Wall? The sound ratings seem really good:

• Power: 110-120 V / 60Hz / 4.0A / 940 CFM
• Noise level: 0.5 - 3.2 sones

Any reason why I shouldn't buy Kobe IN2636SQB-700? We can't seem to make a decision on this. Hood is next!!

I read somewhere how someone saw a vent a hood and kobe at the same place, same cfms, and the kobe was louder. I'm with you on this dilemma as we're going through it as well. It appears that I'm going to spend more on the hood than I did the range... seems backwards to me, but it is what it is. Hope your search is nearly done (I have 2 weeks to pick one as the "run" will be different depending on the style I pick). I've read the zephyr tempest II is relatively quite, but it's subjective.. so.. I also read that the zephyr SS is slightly off from the color of the bluestar... that I am trying to avoid (I was sold on the tempest II prior to that revelation).

Hey Eric, what did you pick? We have been stalled on the reno due to various family health crises. We need to pick a hood and move on with our lives.

I can get the company name if you want (they sell lot of high end stuff on the cheap). Don't see it on ebay anymore, and not sure what size you need.

Fantastic Eric! Great price. How is the noise level?

Even on high it's quieter than the OTR microwave we had before. We can easily have a conversation over it. On medium or low it's hardly noticeable.

As you can probably tell, we have yet to decide on a backsplash... ugh.. definitely one of the harder things for us thus far.

That sounds great Eric! I'd have to do some sleuthing to find a source that would ship to Canada but I appreciate your taking the time to share your hood experience. Congrats on your beautiful kitchen!

LOL, we've been renovating for 1.5 years so a backsplash is the least of my worries. Our current hood is hilariously NOT over our BlueStar range. Yes, the smoke alarm goes off. A lot.

We don't use our hood on all occasions, but it's handy for those frying/stir fry sessions.

We've been really happy with the way everything turned out. It was a long process, but we're happy to say that outside of the backsplash we're finished. Though, until we get one we can't call for final inspection on our permit... lol

I wound up putting a Vent-a-hood with the same CFM over a 30" Wolf. It was the best I could find running 6" duct. It's very quiet. I like your install as well. FWIW the Vent-a-hood was almost the same price. The only thing negative I have to say is that it's not quite enough CFM for the Wolf since the oven vents out the front from the bottom of the range (yes that's a RPIT*). It's totally adequate for the cook top just not for a self clean cycle.

Check this hood, Victory Twister MAX, assembled in Canada. Great hood, Video

Direct capture and containment of oven self-clean effluent is difficult for an over the range hood (because it doesn't overhang the range enough with appropriately increased air flow rate) and is totally impractical for normally mounted wall ovens (because the capture area and flow rate would have to be enormous). All one can hope for in practical residential settings is room air clearing by the time the self-clean cycle ends.

I have a supplemental ceiling vent over my wall ovens. Its 1000/600 (nominal rated/estimated actual) cfm supplements the main hood's 1500/900 cfm. In spite of this available air flow rate, a single Wolf oven's self-clean odor builds up to an annoying level before gradually diminishing. Thus I limit oven cleaning to days when windows can be wide open.

kas

feisty68, I would be keen on knowing what you ultimately decided on. I'm in a very similar situation and noise is important to me.

I just installed a Vent-a-hood 600 and I can barely hear it. Note that what I did was have the 8" duct that comes out of the hood connect to 10" ducting. I suspect that if I had the room and gone 12" it would be even quieter.

Rereading this thread in its entirety -- a trip down memory lane -- reminded me of some web sites with filters on their search function such that when one clicks on enough constraints there are no candidates left to purchase. feisty68's constraints have a similar effect.

Thinking that maybe there is some way out of the box, two concepts come to mind to bring up:

(a) One can choose a hood with internal blowers (as seemingly required) that has more specified flow than the external duct can handle. In this case, at full power the flow will be low, (or possibly zero, depending on the fan curve shape), but when run at part power to yield an appropriate flow rate for the duct, there should be reasonable flow. Whether this is adequate flow would require some analysis. At partial power the blade tip speed will be less and lower noise should result.

For example, a VaH hood with two motor squirrel cage fan assemblies run at part power would likely still expel grease onto their housings as intended. Choked flow, however, may be sooner (CFM-wise) than a similar over-sized conventional blower / baffle system due to the nature of a squirrel-cage blower (as implied by VaH CFM vs. pressure loss data). I wouldn't want to guess which approach was louder at the power setting that was at the point of diminishing returns, CFM-wise.

Related to this category is using an inline axial blower designed for higher pressure loss at the desired actual flow rate. Fantech might help here. Such blowers may be noisier, so an in-line silencer on the hood side of the blower might be essential. There are screaming-mimi aerospace fans that can push 1600 CFM through a six-inch duct.

(b) The other concept is a hybrid exterior/recirculating hood scheme. I think both Best and VaH have examples of recirculating hoods. In this concept, if the actual systems are so configurable, the path to the filter pack would be split with one branch going outside. When the pressure losses of the exterior duct path rose high enough as blower power increased during heavy cooking, additional flow would be through the filter pack and back into the room. Some recirculating hood users here have commented on effectiveness and noise and their threads might be discovered and checked for relevance.

Obviously, the simpler approach here is recirculating without engaging the external ducting. In that case, a separate soffit blower, soffit face register scheme could be used for further kitchen overall ventilation, helpful (slowly) when the oven is opened.

kas