I have the 36" Broan Elite (the shorter version but I think it has the same guts). It's over a 30" gas range with a lot of BTU. It does a really good job at sucking but it is noisy on high. While my wok cooking is bad, my seasoning of a wok (as well as a 18" cast iron skillet that totally did not fit under the hood) demonstrated that it works well. It also passes the bacon test.

I have cabinets on either side of the hood and the range and hood are pulled about 6" from the rear wall. The front burners are mostly (not entirely) covered but I make enough smoke at times to see where it goes and it's satisfactory.

If you are tall enough to use the back burners for Asian-style cooking, you'll have even better results.

Maybe consider pulling the hood from the wall a few inches--that would require getting one that is meant to show the sides though!

The CFM per BTU/hr rule of thumb comes from commercial (and fairly standardized) cooking appliances vs. their (fairly standardized) overhead hoods.* Neither the cooking zones or the hoods are a particularly good match to their residential counterparts. A better rule of thumb, in my view, and more aligned with the action of the hood, is to ensure that the velocity of the air/effluent that reaches the hood baffles is high enough to ensure that there is no smoke reflection from metal parts back into the room.

I recommend a velocity of 90 ft/min. Because we don't have a way to shut off parts of the hood that the effluent doesn't reach when only certain burners are operating, this velocity has to be achieved over the entire hood aperture. Hence, the hood requires an actual flow rate of 90 CFM per square foot of aperture, independent of the number of burners that are operating. (This is for maximum cooking surface temperatures (smoke point of peanut oil, for example, when wokking) and for gas burners. With induction, there is no combustion hot gas entrained in the cooking plume and its velocity is a bit less. At lower temperatures, the flow rate can be lower because the rising effluent velocity will be lower. However, at low air speeds through the baffles, there will be less grease collection by centrifugal impingement. I successfully use about 90 ft/min over my induction cooktop and nearby induction wok hob with an island hood. Your plumage may vary.)

Our hood blowers use a fan blade design that only supplies the flow rate listed for the fan at zero static pressure across the blower; i.e., with the blower hanging in free air. When mounted in a hood, or in a duct, or on a roof, the blower sees restrictions. These include the baffles (or mesh filters), the pressure losses from turbulence -- both at transitions and from the duct walls -- and from similar such losses in the make-up air (MUA) path.

There is always MUA. How much you get vs. how much you need determines what the actual flow rate of the hood will be due to pressure losses across the blower. So whether or not a municipality requires a deliberate MUA system, or the cook opens a window, there has to be good flow into the kitchen to make up for the flow out of the hood. Else there won't be much flow out of the hood.

Even with reasonable MUA, there is enough pressure loss in the loop from cooktop to outside and back to cooktop to significantly degrade the rated blower CFM. I recommend choosing a blower that is rated at about 1.5 times the calculated required CFM from the 90 CFM/sq. ft. rule.

There are also safety aspects of adequate MUA that may apply.

Hood overlap is important to minimize the grease that escapes the hood and condenses on the rest of the room. In a wall application where there are side cabinets, the air flow toward the hood helps direct the rising effluent toward the hood, so the hood's effective capture aperture may be a bit larger than the physical aperture, particularly if there are no drafts that displace the smoke away from the hood. Mounting the hood out from the wall can also help, but the filler plate at the back should be angled to aid reflecting the effluent toward the aperture rather than down.

kas

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*For a description of both methods of CFM requirements estimation (from a commercial point of view), as well as images of smoke capture and containment vs. smoke capture and failed containment, see Greenheck's "Kitchen Ventilation Systems Application and Design Guide" (KVSApplDesign_catalog.pdf) available from their website.

http://www.greenheck.com/media/pdf/otherinfo/KVSApplDesign_catalog.pdf

MUA is also addressed in this paper. Note that all Greenheck CFM requirement values are actual flow rates, not blower CFM rating rates, and that balanced air pressure MUA is present in the commercial kitchen.

Exhaust hoods do not removes odors. They remove grease, smoke and moisture. You could have the best hood in the universe and it will not remove odors. Hoods will remove the grease droplets that contain odors, but if for example you are cooking fish, a hood will not remove the fish smell. To minimize odors, clean your pans, utensils and cooktop that cooked the odorous foods immediately, and use a garbage disposal for the leftovers (if you don't have a garbage disposal, take the trash with the odorous items out immediately). Your hood's filters will retain the grease droplets that have the odor, so clean the hood filters immediately too.

A good hood needs baffle filters, needs to be at least 24" deep, minimum 600 cfm, installed 30-36" above cooktop, no more no less, and needs a duct diameter of at least 8". That about sums it up.

Thanks Fori, for your input, still not 100%, which hood. I hope not to bump the range hood out because the way my kitchen is laid out, my range hood is directly next to a window (left of range hood) and on the right, it is opened with no cabinets.

Thanks, Kaseki, When you said "aperture" do you mean the area of the opening? See attached. I took a few models that I was looking at and highlighted what I think the aperture would be. I just want to make sure I understand it, for science!

^ Elica Titan

Thanks M Miller for the clarification of the odor. Based on all these comments, it seems like I definitely want to go with the next step higher. For the Elica range hoods, there is nothing in between, so I would end up having to go with the 1200 CFM blower.

At this point, should the 1200 CFM blower be internal or integral? Elica has them integral. Hopefully, that won't be an issue.

Thanks all!

Aperture Definition

For flush baffle hoods, like those shown above, I would define the aperture to be the baffle space that you have outlined in red. For recessed baffle hoods, like Wolf hoods or commercial hoods, it is the inside area of the bottom of the hood.

Capture

On other point w.r.t. the lower image above: The baffle space is much smaller than the overall hood area, and without a decent lip and cavity rising effluent (cooking plume) can easily reflect from the flat surfaces and escape. Such a design may work if there is sufficiently high air flow, but not having experimented with such designs, I am uncertain whether 90 CFM per sq. ft. for the entire base area would be sufficient to ensure containment by the modest baffle area.

Note also that this design doesn't actually perform the two-step commercial hood process of capture and then containment, it only captures what it contains (moves to the other side of the baffles). Using a sub area of the base area for baffles will, at best, make for a noisier hood when the air flow has to be a lot higher than baffle function (centrifugal impingement) alone requires.

Design

My view on hood design is this: One of the highest expenses for commercial kitchens is the power expended on ventilation and make-up air conditioning. This has led to hood designs that strive to maximize ventilation performance per kilowatt expended, which also saves on MUA movement and conditioning costs. Residential hoods have a higher need for aesthetics than most commercial applications, and due to intermittent operation, a different balance between electricity cost and ventilation capital cost. Nonetheless, deviating too far from the basic commercial design will penalize the hood in either capture and containment or noise or some other performance factor that may result in a less-than-satisfactory residential experience.

The more aesthetics drive the solution, usually the poorer the performance. In the limit, as in poser kitchens shown in magazines, there is no hood at all. Even this extreme case is consistent with a useful hood maxim: performance, affordability, aesthetics -- pick any two.

Internal vs. External Blower

If a blower external to the hood can be put far enough away from the hood, the fan blade tip turbulence noise will be somewhat attenuated -- quite attenuated if space along the duct path is available for a silencer. If the hood is mounted to a wall and the choice is either an internal blower or an external blower on the other side of the wall, then differences in noise will be slight. In such a case access to the blower for repair might be the main consideration, or perhaps options for dual dampers (best in cold windy climates) may be affected.

kas