The rising effluent from a pan or griddle will expand as a cone as it rises. The half angle of the cone can be as great as 23 degrees for very hot griddles. Further, the greater the separation, the more susceptible the rising column will be to cross drafts. Because of these factors, when ceiling capture is used in commercial settings the size of the "hood" is very large. In some cases the entire ceiling is perforated, and the space above it kept free of grease by the use of intense ultraviolet light.

Another point worth reviewing is that hoods provide very little "draw" down at the cooktop, even when the distance is only 30 inches. It is the velocity of the rising effluent that the hood depends on for capture. The primary purpose of the high flow rate is to assure that when the effluent reaches the baffles it does not reflect off (shown in Schlieren photographs as curling away) and escape the hood. (See page 4 of the linked pdf Optimizing Makeup Air - Food Service Technology Center.)

Downdrafts are basically useless. We're not going to get into a ton of details, since there's already plenty of material on this topic. Suffice it to say that if you're planning on serious cooking, you will NOT be happy with a downdraft. Overhead range hoods are the way to go.

Regarding ceiling height: most overhead range hoods are installed about 24" - 36" above the cooking surface (varies by brand, we recommend 26"-30" for best performance as well as keeping the lights below the eye level). If your ceiling is too high, there are extensions available for most range hoods, or you could build a "soffit box" to bring down the ceiling at the hood's intended location. Here are some examples of soffit boxes: FuturoFuturo.com - FAQ - Sloped / High Ceiling

I have used a down draft range for 15 years in an application like you describe. We are avid home cooks. We have been 100% satisfied with the performance of the downdraft fan system of the Jenn Aire stove we own. The fan is very powerful and has multiple speeds. One small issue is that the flame of the gas burners can be pulled slightly toward the fan. We have always been able to work around that issue with no impact on cooking even with low flame and no impact on the performance of the fan. I would not hesitate to purchase a new downdraft stove. The advantages in circumstances like you describe vastly outweigh the disadvantages in my humble opinion.

I agree with rpg51. Down drafts can and do work when they are vented correctly. I worked for Jenn-Air (pre-Maytag / Whirlpool) and saw many in-home installations. Most done properly and some not so good. ie. back to back elbows, wrong size duct work and flexible duct work. Are they perfect? No. If you know what the limitations of a center down-draft are ahead of time you'll not be disappointed. Rear telescopic down-draft work very well too. Again, with all venting it needs to be done properly.

Best Cattura 18" Down-Draft

With regards to the Best Range Hood Cirrus built-in hood. Yes they do work. See the video link below. Here is my question to you. Who in your house is climbing-up the ladder to take down the filters and clean the stainless. Maybe not be bad at 9-ft leve but may be more of a PIA in at 12-ft. height.

Best - Cirrus Range Hood

Please note that the comments made by Futuro Futuro Kitchen Range Hoods is a company that does not offer a down-draft or true flush mount ceiling hood. If seems that if they can't complete in the category it is much easier for them to poo poo the options you are considering because they don't have anything to offer. To be fair to Futuro their hoods look like a direct hood import from Italy and seem to of reasonable quality. But, unless you're in Brooklyn, NY or Hallandale, FL it is difficult to truly judge the quality and the long term support for service. Ask those folks that who own a Elitair or TecnoWind hood and that are now orphaned.

My recomendation is to look towards a nationally distributed brand and your local dealer for suggestions and long term support.

Please let us know what you finally decide. Good luck.

Hektor, what did you go with?

Sophie -

Dacor has a line up that features a downdraft that's compatible with their ranges.

dacor Downdraft