The only one that comes close to meeting the performance requirements would be the Kobe RA-02.

For a 100 bucks more you can upgrade to the 42". If that fits into the area that is what I would get hands down. It will expand your capture area to fully meet your venting requirements.

Capture: Getting the effluent into the hood. Generally a function of the hood size and distance above the pans, in other words, the hood overhang relative to the expanding rising effluent plume. Cross drafts can also degrade capture.

Containment: Keeping the effluent in the hood long enough for the fan and ducting to get rid of it.

Example of failed containment: Smoke rises into hood, curls around, and get out of the hood before being exhausted. Steep hoods tend to reflect upwards until the smoke reaches the baffles/meshes. Flat hoods tend to bounce the smoke down if the air velocity is too low.

If the air velocity everywhere at the hood aperture is at least the effluent upflow velocity, around a meter per second, all captured smoke should be contained. Otherwise, the hood has to direct the smoke toward a smaller sectional area where the velocity will be higher for a given flow rate.

kas

wow, kas, thanks...

so just theoretically, would you say a flat 940 cfm would be more or less effective than a 760 cfm with good containment (a deep inverted V shape)?

the reviews, though few, of the futuro futuros here have been so darned good, even though almost all of their hoods are flat and 940 cfm. i'm wondering how credible those reviews are now...

i get that the big kobe would be most effective... i just wish it were a tad more elegant and cheaper!

There are no "performance requirements". 100 CFM / 10000 BTU is a rule of thumb fwiw, but it depends more on how you cook. Strictly speaking, I don't think a hood is even required for any consumer range. It is all a matter of comfort. Of course, you'll be pretty uncomfortable if you don't get one ;-) And yes, it should probably move at least about 600 CFM of air, but I caution you not to get too caught up in the hood overkill craze. The larger hood will work better in general. 24 is a nice depth. If you can go to 42" wide that is a good idea too. Height also makes a lot of difference: low works much better, but melts and catches fire, high looks cool. Pick something between 28-30".

So my recommendation is to focus more on size (width and depth) and less on CFM. Do not rely on CFM to make up for a small physical size or you will have too much noise.

At 600 CFM use a minumum 8" round duct. at 1000 a minimum 10"round or you will waste you CFMs overcomming resistance.

You can't blow air out of your house unless you first suck air into your house somewhere. Either open a window or otherwise provide make up air, or you won't get anywhere near the rated flow. Oh, and your furnace flues may run backwards and other deadly stuff like that. Do you have radon in your area? a basement? mold? Just open the window ;-)

Hello, just wanna throw in my 2 cents, I have a 30" over a 30" and I regret every bit of it because the hood simply can't catch everything that the side burners/pots are throwing at it. Plus, if you have other things such as a rice cooker in the vicinity, that steam's not gonna find its way out of the kitchen very easily. If it were me, I would pick the size, and then work the complex price/CFM/brand/effectiveness/reliability/style math. Hope this helps. :)

Does this flat hood have an aperture out to its edges?

Reviews may be colored by past experience with inadequate ventilation and by sensitivity to odor or lack thereof.

One way to look at the situation is that one has one or more pans/griddles/etc. on burners of some type. The part of the pan that is hot is cooking the food. The burner, if gas, is sending combustion products around the pan and up. (One hopes not to have combustion products from within the pan unless Bananas Foster is on the menu.)

Anyway, the rising effluent expands as it rises from the area it started from. The rate of rise and angle of expansion varies with burner type and other factors (I can provide a reference if anyone really cares), but a good model is an inverted right circular cone with the cone peak below the pan so that the edge of the cooking area is encompassed by the cone and the base (wide part) of the cone is at the hood. The total cone angle will be around 45 degrees and the velocity will be around 1 meter/second.

So why put the hood at a head-banging 30 inches above the cooktop? To allow a smaller hood to capture more of the expanding effluent because the effluent hasn't expanded as much as it will at 36 inches.

Now, as it happens, hoods and other types of transitions between ducts with flow and the room environment are very bad at pulling in air from the sides. They best pull air from the region below the hood aperture. Even then the flow rapidly drops as one moves down away from the aperture, so one should not expect a hood to suck up the effluent from the region of the cooktop. This means that hood function depends on rising effluent, and also that any expanding effluent that misses the hood aperture will not be immediately exhausted, and will either precipitate on the house surfaces (in the case of grease), or be exhausted gradually as the air in the house is replaced.

As to whether a flat hood equals a peaked hood, maybe the problem can be simplified. Suppose both hoods have the same aperture. In order for the mesh of the flat hood (baffles need peaked hoods to work) to pull in the rising effluent without any of it reflecting downward, the air flow has to equal the effluent rate of rise everywhere in the aperture reached by any cone base.

I'm not going to pull out a calculator, so let's use easy numbers. Let the hood be 3 ft by 2 ft and the effluent velocity be 3 ft/s. Then the flow into the hood aperture has to equal 18 cubit feet per second or 1080 cubic feet per minute. This would require a blower rated at around 1500 cfm because the ducting, transition losses, and mesh losses, as well as the negative pressure pulled in the house even with MUA, will drop the flow rate from that specified for the blower at 0 static pressure drop.

Even with this setup, any effluent that isn't directed into the hood will spill into the room.

A hood shaped like the Wolf Pro Island Hood has baffles inside sloped upwards. There is little obvious concentration in this shape at the baffle area so it too would seem to need the same flow rate and corresponding blower as the flat hood. In reality the air flow at the baffles is somewhat complicated and effluent that isn't contained near the hood edges will rise and be contained higher up. If the baffle shape is correct, effluent hitting the baffles will not escape.

In general baffles will be more effective than flat mesh filters if the mesh is allowed to acquire grease and dust that reduces the flow rate of the system it is part of.

If one looks up into a commercial hood, one often sees that the baffles are only on one side and that the other side is designed to taper toward the baffles. In this case there is obvious concentration toward the baffles and the flow rate at the aperture can be lower so long as it meets the required rate at the baffle area. Note also that commercial hoods have deep cavities that are ideal for aiding containment.

A hood shaped like a hip roofed house would provide concentration in two dimensions and potentially meet required performance with less flow rate if it has a mesh filter high in the concentration area. This might make cleaning difficult.

The above has to be understood in the context that in general, all the burners are not in use generating grease vapor, and a trade-off between size, cost, mounting, ducting, rate of odor removal and aesthetics has to be made in most residential circumstances.

Duct size should provide for an air velocity of 1000 to 2000 feet per minute in the duct (at full flow) to keep the smaller grease particles suspended. No baffle/mesh/filter scheme removes all the grease at the filter.

kas

I checked out the links you provided, and noticed that the Kobe RA-02, while a little more powerful, also has a pretty high sound rating, 8 sones.

I'm not an expert, but one of my friends has a Ventahood in her kitchen, and while it's nice, even at 6 sones it's already so loud that you can't have a conversation.

What's the point of having a more powerful hood if you're never going to use it's full capacity b/c its too loud?

Just wanted to clarify. My 30-over-30 setup, I meant to say that I have a 30" range with a 30" hood over it, not a hood installed 30" above the range, if that's what kaseki was referring to. My bad. :p

Interesting you're buying a Wolf 36" AG but not the Wolf wall chimney hood...

I'm buying a 36" BS, but going with the Wolf hood.

Any reason you don't like the Wolf hood?

I'm going with the 42", and leaving a 2" gap between the hood and the gap framed on each side. I wanted the 42" over 36" as I'll use the grill for winter-time indoor cooking. I have 11 ft ceilings, so I have to have the pipe part (flue?) custom made. I'll use an outside 1200cfm blower, and I've remembered to ask that the piping and elbows in the attic use smooth surfaces and rounded not squared corners/curves.