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super-quiet 600+ cfm range hood for condo - mission impossible??

Posted by feisty68 (My Page) on
Thu, Mar 6, 14 at 18:15

Pretty please save me from hood research misery?! I have read many threads and articles on this, but I still don't know what the best solution is for my needs. Here's my set-up:

This post was edited by feisty68 on Thu, Mar 6, 14 at 18:17


Follow-Up Postings:

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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

* range is 30" BlueStar RNB
* planning 36" wide hood
* 6 ft horizontal duct leads to exterior walkway
* I *think* the duct is 6"
* don't want glass
* easy to clean

I am very sensitive to noise. I spend a lot of time in the kitchen cooking multi-course scratch meals for a family of four every.single.night. I like to talk to my family or listen to music or the news. I know myself - if a hood is too loud (like my current one) I will simply not use it.

I roast and fry and wok and regularly set off the fire alarm in our single level apartment where the cooking odours and smoke go *everywhere*.

Another issue is that our windowless bathroom needs a bathroom fan and it's not uncommon that someone takes a shower or bath when I am cooking. Then the bathroom fan starts "fighting" with the kitchen hood, drawing odours down the hall from the open concept kitchen.

I was very interested in exterior/remote or inline blowers to move one of the sources of noise away from my head, but according to Modernaire they should be at least 10 feet from the actual hood - my hood would only be 6 feet from the outdoor duct outlet. Plus I will have to open the window for makeup air and then I would be listening to the external blower through the window. Not to mention the risk of annoying neighbours with the blower noise. My husband said that in his last kitchen he installed an external blower but because it wasn't far enough from the range, it was pretty noisy and not worth the hassle.

Although I really care about the looks of this kitchen, I can live with a hood that is not about the looks if it's *quiet* and really works.

I know there is someone out there who can advise me :)


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Makeup air isn't a huge issue for us though - in-floor radiant heating, not air.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Can you go 36" wide x 27" deep and mount it 32" off the counter top, use a 600 cfm blower with an 8" duct ?

Advantages of the above are

1) Extra width and depth means smoke and grease can get in the hood easier with less blower power / noise.

2) 8" duct will be much quieter than the 6" duct you mention.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Thanks for your reply trevorlawson! Yes I could do what you recommend I think. I would have to use a 8" to 6" duct transition at the exterior wall though. I can't alter that due to building rainscreen issues, etc. When you say 600 cfm blower - do you mean in the hood or external? Any brand/model recommendations?


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

If you can't change the outside hole from 6" to 8" then you have the best you can do, but it will be louder than you want. For a Bluestar range you need air flow restricting air flow makes more noise and less effective smoke and grease removal :(

This makes it more imperative that you over size width and depth. You will need to go with an internal blower, if they wont let you increase the hole size to 8" i doubt they will let you put a huge box on the outside wall.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

At a given flow rate, noise-inducing airflow turbulence through baffles and along a given duct path will be independent of the fan. However, blade tip turbulence will be less with a larger fan run at a slower speed. In any case, the fan curve should support the modest pressure loss at the 8 to 6 inch transition, in addition to baffle loss, hood transition loss, duct loss, AND inadequate MUA loss (negative house pressure).

There is always make-up air (MUA). The less there is the less air that the hood can move out of the kitchen, no matter what the fan rating is. I can only guess that the reference to radiant heating was intended to conceptually connect hood MUA to a furnace or A/C system MUA. However, furnace and A/C MUA is not normally of the same scale as needed for replacement air for a 600 cfm hood.

To get the hood to flow air it will be necessary to provide a path to the outside that is relatively low pressure loss, e.g., in this case an 8-inch duct with damper or equivalent open window. (Heated or air conditioned MUA is a bigger issue ignored here.)

If there are any combustion appliances in the house in contact --- air-path-wise --- with the kitchen, then a house negative pressure greater than about 0.03 inches of water column can back-flow the appliance exhaust and potentially pull carbon monoxide into the house. Do not neglect the need for MUA, particularly in tight houses.

kas


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

When I was looking a year ago, Kobe had some if the quietest hoods I saw. We got the 30 in chx191 and love it. Works great and very quiet.

I'd suggest going to a home improvement store with a working bath fan display set up. Get a feel for different noise ratings. Then look at the specs for the models you are considering.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Thanks very much for your comments Trevorlawson!

"For a Bluestar range you need air flow restricting"

Can you clarify what you meant by what you wrote above?

You will need to go with an internal blower, if they wont let you increase the hole size to 8" i doubt they will let you put a huge box on the outside wall.

It's not really an issue of permission from the condo association. It's more an issue of what I would be required to do to increase the hole size on a load-bearing wall that has a rainscreen etc. It's more technical than a typical house...I'm not sure I want to go there. I don't know if a "huge box" would be an issue or not. It would have to not be a head-bumping hazard, and it could not be too noisy because it will be right outside my window, which is often open (no air conditioning in summer). I could possibly get permission if it could be make to look unobtrusive.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

SORRY.... meant to say """"For a Bluestar range you should not restrict the air flow if possible.""""

Moving the blower away from the hood will reduce the noise level in the kitchen, having said that the further away you can place the blower the quieter it will be, you only have 5' which is about half the distance where I could honestly say you will notice a big difference.

I am not sure if using a remote blower ( ie sucking) would be better when going from 6" - 8" than an internal blower (blowing) going from 8" - 6" .... maybe Kaseki could chip in on this question..............


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Kas, I really appreciate you chiming in with your sage advice :)

"However, blade tip turbulence will be less with a larger fan run at a slower speed."

So I should consider oversizing the fan? I think 600 CFM is probably adequate for my needs based on my current NuTone hood which goes up 550 CFM with crummy "J"-shaped ductwork (but which is 2 ft shorter than planned). But maybe I should increase the CFM to reduce the noise?

"If there are any combustion appliances in the house in contact --- air-path-wise --- with the kitchen, then a house negative pressure greater than about 0.03 inches of water column can back-flow the appliance exhaust and potentially pull carbon monoxide into the house."

The apartment is very tight but there is no furnace, no air conditioning, or any other combustion appliances in the apartment. So I don't think there is a safety issue here. Negative air pressure is an issue with the functioning of the bathroom fans (two windowless bathrooms down hall from kitchen on single floor apartment) and the hood - all potentially trying to suck air at the same time.

The MUA source would be opening the kitchen window I guess? As you can see from my plan, however, the window is quite close to the hood location, leading to the likehood of undesirable cross-drafts (diagram below from Greenheck guide). Is there a better way?

Here is a link that might be useful: really great Greenheck guide that Kas linked to in another thread


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Trevorlawson -

"For a Bluestar range you should not restrict the air flow if possible."

Thanks for the clarification :)

"Moving the blower away from the hood will reduce the noise level in the kitchen, having said that the further away you can place the blower the quieter it will be, you only have 5' which is about half the distance where I could honestly say you will notice a big difference."

Yes, Modernaire recommends 10 feet, so I don't think an external blower will buy me much noise reduction.

What about a duct silencer? Fantech says:

"The Fantech LD silencer reduces the "perceived" noise of a kitchen ventilation system by 50-60%. This is particularly important with range hoods where the airflow rate is generally high (300cfm+).

Here is a link that might be useful: Fantech Kitchen Ventilation FAQ


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Hi Feisty68!

Have you looked into VentAHood? I'm not sure what your budget is, but VAH is some of the quietest on the market. Disclaimer: I do sell appliances (Factory Builder Stores in Texas), but VAH is one of the few products that works exactly like it says it does. The ducting is the biggest potential problem that I see, I would recommend you have at least 8".

I wouldn't recommend the remote blower, they don't work nearly as well (pulling air down the duct is a bit tougher than pushing it through) and on top of that, the motor typically is not the main source of noise in a hood. Movement of air in general is going to cause some noise, and it gets louder when it has to move through a mesh or baffle filter. This is one of the main reasons VAH is quieter, there are no filters for the air to pass through because the contaminants are separated through a centrifuge system.

We do offer several different brands of hoods at my showroom, but VAH is definitely the quietest which seems to be your main concern. It also has the benefit of staying at about the same sound level even as you increase the cfm because they utilize multiple blowers. For the hood you're describing, it would most likely have two blowers in it, and you would just increase the cfm by turning on the second blower.

Anyhow that's it for my sales pitch, but I really do think VAH is the best bet for your criteria. ;-)

Here is a link that might be useful: VentAHood Magic Lung


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

The fantech silencer does soften the noise, your issue might be the the size of such a unit its over 10" round.

While I respectfully disagree with most ares RodneyFBS posts, he does recommend the 8" duct which I feel you should revisit just in case its at all possible, even if it means more work / more money.

Your range will most likely produce more smoke and grease than you are used too. effective venting is very important in order for you to get the best out of your new range.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

I would be able to buy this range hood locally:

36" wide but only 19" deep
6 speeds
6.5 sones highest speed - 860 cfm
1 sones lowest speed - 200 cfm
made in China
19 gauge steel
6" duct

Here is a link that might be useful: Spagna Vetro PSF-36


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Thanks for the VAH recommendation Rodney. The link you shared indicates this:

-600 CFM Magic Lung® Blower
-6.5 Sones (At High Speed)

6.5 Sones - to my ears - is quite an intrusive noise level. Can you provide the CFM/Sone ratings for lower speeds of the VAH?


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Hi Trevorlawson,

I am already using the new Bluestar. Adore it :) . It actually opens the door to cooking differently because the burners can go hotter. And yes, there definitely is more smoke/grease as a result.

I will investigate how feasible the 8" duct would be.

Diameter of the Fantech silencer isn't really that much of an issue. There are no upper cabinets, and if the silencer didn't fit in the soffit, the soffit could be redone. We will be doing drywall fixes towards the end of the reno anyway. It sounds like it could play a significant role in reducing noise.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Thanks for your Kobe recommendation Williamsen :) . I will be looking into that brand based on its reputation for quiet. The models that have the quiet setting of 1 Sone/300 CFM interest me.

"I'd suggest going to a home improvement store with a working bath fan display set up. Get a feel for different noise ratings. Then look at the specs for the models you are considering."
I feel like I have a baseline for the Sone ratings based on my current hood which ranges from 4.5-9.5 Sones. Basically, I have to be desperate to turn on my hood. The problem I find is that many manufacturer only give noise specs for the top setting (which is usually overkill for normal cooking) and sometimes the lowest setting (which isn't necessarily even enough for normal cooking). For example, the Chinese hood I linked to above that is rated 1 Sone/200 CFM. Pretty quiet, but is that enough CFM for normal cooking?


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Here is another locally available option:

made in China
36" wide x 24" deep
Airflow (Q/L/M/H) 400CFM / 600CFM / 800CFM / 1000CFM
Noise Level (Q/L/M/H) 1.4Sone(45dB) / 3.5Sone(58dB) / 7.0Sone(68dB) / 8.0Sone(70dB)
designed for 8" duct
19 gauge steel

Here is a link that might be useful: Spagna Vetro PS09-36


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Kas wrote this in another thread about a 36" wide x 24" deep hood:

"The actual flow rate needed for a six square foot aperture size is probably only a nominal 540 cfm (for wokking, frying, and searing), so selecting a fan in the 800-900 cfm at zero static pressure range should be good enough for the pressure losses from ducting, hood transitions, bends, baffles, and make-up air restrictions, and typical fan curve performance. Obviously, with a list of items that long, the actual restriction pressure loss can widely vary, but I think the factor of around 1.5 should be enough to make up for several sins."

800-900 CFM sounds like a good guideline for me as well :)

Here is a link that might be useful: yet another hood thread


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Is this the one for me? I love that Kobe publishes the CFM/Sone ratings for each speed!

QuietMode™ 300 CFM (1.0 sone)
Speed 1 370 CFM (1.4 sones)
Speed 2 440 CFM (2.8 sones)
Speed 3 540 CFM (3.5 sones)
Speed 4 640 CFM (4.2 sones)
Speed 5 760 CFM (4.5 sones)

22" deep

suitable for 6" duct

underside is somewhat concave which should improve performance

retails CAN$1200 - ouch but not insane

Here is a link that might be useful: Kobe CH9136SQB-1 (36

This post was edited by feisty68 on Fri, Mar 7, 14 at 16:36


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Focus on depth ............ width and depth is the key to giving you a chance.............


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Kobe also has 36" x 24" deep models (RA02 and CH100-1 series), but their lowest settings are 300 CFM/1.8 Sones. Given that the lowest setting is probably what I'd use for everyday cooking, I'm not sure I'd want that extra noise.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

For example, 36" x 24"

300 CFM/1.8 Sone
580 CFM/4.7 Sone
760 CFM/5.4 Sone

Here is a link that might be useful: Kobe CH0036SQB-1


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

ok super honest time......... low cfm's low noise does not work with a Bluestar. Moving air makes a noise. As I have said many times, If your in a jet at 30,000' noise is really good thing to hear, when it goes quite you are in big trouble, because the ENGINE is not sucking and blowing.

You have two options as I see it

1) Will it suck enough smoke and grease out of my house that my alarms wont go off ?????

or

2) will it be quite?????

I don't think you can successfully have both with an internal blower, it makes no difference if its a Kobe, VAH or ModernAire. Your option is noise level or optimum function to remove smoke and grease ....

You selected the Bluestar range which means that function and ability is way more important than good looks, stick to that train of thought FUNCTION, FUNCTION, FUNCTION.

IMO........ Trevor


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

I see what you're saying Trevor. So you're confirming that it's mission impossible ;)

One thing that I wondering about is whether it's possible to mount a 22" hood outward from the wall to achieve better capture above the cooking surface? I think I saw that done in someone's thread. She used a stainless steel filler piece to cover the area between the wall and the hood. I am almost always doing grease/smoke-producing activities on the front burners so really that is where the capture area is most important.

I can't go too deep with the hood though. The bottom of the hood needs to be at 66" above the floor (5'6") based on manufacturer recommendations for BlueStar and Kobe. That is fine for me because I am 5'5". But my husband is 6'2". For one there is a serious head-bonking hazard. Also, if it's too deep he won't even be able to see what he is doing. Realistically 22" deep might be the limit...


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

So it looks like wall extensions for hoods do exist and they are for improving coverage of the hood over the cooking surface:

Seems cheaper/simpler than getting an overkill hood just for the depth?

Here is a link that might be useful: an example: Best brand 3


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Kas' comment on this:

If an extension is used and has enough slope to ensure that rising effluent reflects upward and the flow rate is high enough to keep it contained, I would expect effluent to be captured over the wider area. This requires the insert to be higher in the canopy to leave room for the extensions.

Here is a link that might be useful: range hood hell thread


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Apparently, Spagna Vetro=Cavaliere Euro


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Wow! This thread grew a bit while my back was turned. I owe an answer to somewhere up the thread.

feisty68 wrote, in part:

[kaseki wrote in part] "However, blade tip turbulence will be less with a larger fan run at a slower speed."

"So I should consider oversizing the fan? I think 600 CFM is probably adequate for my needs based on my current NuTone hood which goes up 550 CFM with crummy "J"-shaped ductwork (but which is 2 ft shorter than planned). But maybe I should increase the CFM to reduce the noise?"

By oversizing I meant a fan rated for higher flow rate at whatever pressure loss is estimated to apply to the configuration, BUT, running it at whatever lower speed is necessary for the hood to capture and contain the effluent.

That was for noise abatement, not neighbor pitchfork raising. The number one issue as Trevor has pointed out is that the hood has to overlap the rising effluent. Contrary to popular perception, the hood does not suck up the moisture, grease, and odor from the cooktop; it keeps the rising effluent (at up to 3 ft/s velocity) from "reflecting" out of the hood. Very little capture is performed outside the hood overhang. (If you fill your house with smoke, the hood will eventually remove it. Time required to 1/e^3 of the original concentration will be roughly three times the house volume divided by the actual hood flow rate assuming open windows in every room.)

So, yes, if there is one burner that is used for the noxious effluent cooking, then it would make sense to place the hood to ensure that the expanding effluent from that burner is captured by the hood aperture size and position. Generally, though, one wants a large hood aperture overlapping all the burners. There is a lot of tolerance in how high a hood can be from the burners, but the hood aperture has to grow as the height is increased. Hence the large area of commercial hood apertures set 7 feet above the floor.

Setting the hood away from the wall works if all the needed sheet metal to direct effluent that tries to escape behind the hood can be placed where needed.

And I can confirm that Fantech's silencers are significantly larger than the ducts they mate to. These units mainly reduce the higher frequency noise generated past them away from the hood. And this noise is mainly blade tip turbulence noise.

kas


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

Thank you Kas! Very helpful clarifications.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

So here's the problem. My situation is a countertop 36" above floor and the 30" BlueStar range trim adjusted to 11/16" above countertop (BlueStar installation requirement). Kobe recommends a hood height of 30" above cooktop. If you use a 27" deep hood (possibly by building out shallower hood from wall), you end up with a serious issue for a 6'2" chef (shown in green below) - not just head bonking but even visibility. IMHO, a little ducking doesn't address this issue adequately:


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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:


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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?


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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. ;-)


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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).


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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).


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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).


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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.


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RE: super-quiet 600+ cfm range hood for condo - mission impossibl

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


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