Sorry it's taken me awhile to get back here. Thanks for all your responses....some very helpful info here. Angie_DIY......Here is a link to the GE hood we're considering. After reading the manual I realize that the charcoal filter is only needed if you're using it as a recirculating fan. We won't be. There is also a grease filter that is washable. http://products.geappliances.com/ApplProducts/Dispatcher?REQUEST=SpecPage&Sku=PV970NSS michoumonster.......that makes sense, and I certainly would not be using the fan on high all of the time. But some other comments have mentioned that code often has a limit on how many CFM's are allowed. We're moving to a small little community where they are sticklers about code (we've had fits with them on several other issues), so we'd better check to see what is allowed first. GWlolo.....Yes, I've read that the hood should be slightly wider than the cooktop. Ours won't be unfortunately. We have a 30" cooktop and a 30" hood, but I guess the range hood will extend beyond the actual burner area, so I think we'll be okay. I have to confess that until recently I didn't know that range hoods removed odors from cooking. For years I had a Thermador down-draft cooktop, and the fan was so loud that it honestly sounded like a jet engine taking off, so I didn't use it except on rare occasions. It's nice to know that in my new kitchen I'll be able to get rid of smells like brussels sprouts! A2gemini.....I agree...that's the only way I'll make bacon anymore, and I just learned this method about a year ago. BTW, we do live in a cold climate, and we do have building codes to contend with. But I didn't realize the hood CFMs would have to be considered. See above where I talk about this. I guess I have some checking to do. WileyBob.....I agree about Thermador....I never liked my down-draft, and I had it for about 20 years. I finally replaced it with a GE Monogram cooktop. I like it much better, but I still rarely use the down-draft. I'm looking forward to having a normal hood above the cooktop. I won't need anything as powerful as you need with your Wolf though. I've heard great things about the Wolf cooktops. Detroit burb.....I wish I had read your information before I started my research on range hoods. Good info there! The thing I've had the most trouble with is finding a 'not-too-high' CFM rated range hood with a low sone rating. We need something not too bulky looking, yet we still want a decent performance. So I think we're just going to go with the GE curved profile style in the link I've posted above. It's noisier than I wanted (7 sones on high), but I'm sure we won't have it on high for long periods of time. My husband and I did your calculations on CFM vs. room size, and I think we'll be okay with that one. Thanks for your help! artemis 78.....I also like the Kobe's, and we were considering going to Cincinnati to look at them (they don't sell them where we live), but I fear the building inspector (they really do inspect here) would think the CFM rating is too high. But I'll check on this.....glad to know you like yours. We're moving to a modest little home (we plan to spend most of the year in our RV), and I'm sure we already have the best kitchen in the neighborhood. We plan to stay in the house forever, so we're making it as nice as we can within reason for the type of house it is. Thanks again, everyone!

Actually, by aperture I meant the opening at the bottom of the hood that intercepts the rising and expanding effluent. The hood may be a bit bigger than this aperture. I believe this meaning is also relevant to Greenheck's use of a 85 CFM/sq. ft. value for certain types of cooking. (Many commercial hoods have thin edges.) Schlieren photography of successful and unsuccessful capture arguably puts the specific flow rate into this range. In some cases where the hood has a flush bottom with mesh filters, some effluent won't be captured due to reflection unless an extreme air flow is achieved, and for such cases reasonableness suggests using the area of the meshes and their close surrounds rather than the entire hood area. It is also true that at an actual 90 CFM/sq. ft., there will be a modest zone of a couple of inches around the hood where passing plume effluent may be captured. Further, baffle designs vary somewhat, and different shaped approaches to the baffles can exist, particularly in commercial hoods. For my Wolf Pro Island hood, the baffle area (mapped onto a horizontal plane) is essentially equal to the inside area of the hood at the base. And just to make this more complex, the actual plumes have different velocities with angle, and with pan temperature, and with presence or lack thereof of hot combustion products. So, in some cases with a large hood providing good capture, less than 90 CFM/sq. ft. may be sufficient, perhaps as low as 60 if using induction, or if no wokking or searing is attempted. And then the value of 1.5X can be debated depending on duct characteristics, losses in baffles and hood, the blower's fan curve, and whether the MUA is pressurized so that the house pressure is very close to equaling the exterior pressure. And last, the calculation leading to 1000 CFM for the blower zero-static-pressure rating implies an actual flow rate given various pressure losses of 600 to 700 CFM, not a particularly extravagant value. So, my suggestion is intended to be an estimate that covers a lot of sins and uncertainties, and which should lead to few complaints about inadequacy. I will not be inspecting your system and handing out black marks for non-conformance, so feel free to juggle the trades between performance, aesthetics, and affordability. When composing a message here, one can do it in a text editor and paste it into the composition window; this might have merit if one has dropouts that cause loss of one's creative effort. Also, one can write in the window and edit to his heart's content, and even change his mind and remove the entire text, then drop the page without submitting. As we aren't allowed html, and extended character sets aren't certain to work, I'm unclear on what advantage results from previewing beyond that which occurs as we write.

Thank you so much, kaseki,colbran, and weedmeister for your very helpful responses. Kaseki, the education you provided was phenomenal, and I really appreciate the time you took to explain the science behind the decisions. I had read the forums fairly extensively, but you have added new depth to the discussions. It is interesting - came home to read these responses after a 2 hour meeting with our contractor. One member of the team is urging me to get a hood that is 450 CFM and is dubious about the need for MUA. They also indicated that I didn't need the 36" hood for the 30" cooktop. (This is a very good company - considered to be one the best in town (I won't say where) and I know we don't have a commercial kitchen. On the other hand, we do use high heat to sear meats and to stir-fry. The person doing the construction diagrams did indicate that the information I presented and the questions I was asking were in fact consistent with safety standards (why you want a wider hood, MUA concerns etc). . It is an induction cooktop, which does reduce combustibles compared to our current gas stove, but I still want to make sure that we remove odors and smoke adequately. Because we live in a cold climate, we would need to address heating the air from MUA. From reading other forums, I get the sense that if I am running the a lower CFM hood at its highest setting, noise is likely to be greater than if I am running a more powerful unit at a lower setting. (Don't know if that's correct or just someone's opinion) I'll continue to read the sources you suggested to see if that is true. So far I can't find any dB information on spec sheets. Again, thanks to all of you for your responses.

Odors are just one component of cooking ventilation. Heat, Odors, Grease, Steam, and Smoke are all what is removed by good ventilation. Those “indoor smog” pollutants affect your indoor air quality negatively. Having them stay in your home affects your health. Multiple studies show that ventilation of cooking products improves that indoor air quality and keeps you healthier. While a retrofit situation may not be able to strive for the ideal, in 85% of my designed from scratch kitchens, the hood will always be specified to be larger than the cooking zone. It is ALWAYS discussed as the ideal, with any client being fully informed and signing off on the consequences of any other choice. When there is is no other choice but to have the same size, planning for it to be as deep as possible is the best solution to limiting the width. In all cases, it is the cooking appliance below and cooking style that determines the CFM needed for ventilation. You will have a low number and a high number based off of that cooking appliance. A high BTU cooking appliance will always have a much higher low number than a consumer grade appliance. Cooking style will increase that base number of the acceptable CFM span. It will never decrease that number. A Wolf range in a kitchen with someone who uses it as an ornament will still need a 600 CFMhood above, merely based on it’s potential. If that potential is lived up to by it’s cook, then that top CFM number will increase. It is the choice of a high BTU pro-style range that has the consequences of requiring that expensive high CFM ventilation system and expensive make up air system. They are inseparable from each other once the choice of cooking appliance is made. It is a package requirement, even though most appliance store salesmen will never discuss that need due to their fear of losing a sale. Instead, they should focus on gaining a sale if they approach the needs for the vent and MUA with the customer. Ventahood or Broan are both good choices. But you need to get with your HVAC specialist to discuss that MUA system. That has to do with climate, local codes that are possible stricter than national codes, and several other details, in addition to the hood power.