These are the links to the wolf cooktop I chose and the hood that was recommended by the appliance representative:

http://ca.subzero-wolf.com/en/wolf/cooktops-and-rangetops/gas-stovetop/36-inch-professional-gas-cooktop-5-burners

http://www.broan.ca/products/product/245684b7-ca08-4a9f-b714-d4787154c0a0

Pro cooking requires pro ventilation. Please review the many hood topics in this forum for an idea of the requirements that apply to hoods. If your purpose in buying a "Pro" cooktop is "Pro" cooking, or for that matter any cooking that yields hot oil or grease vapor, or excess moisture with or without entrained odors, your hood has to capture and contain the cooking plumes from the cooktop pans as well as the burner combustion products that pass around them.

This requires a hood that extends beyond the cooktop in width, and beyond it in front-to-back depth. One would need a rather high (and loud) airflow rate to achieve even mediocre capture with a 15-inch depth hood because the hood flow would have to bend the rising (meter per second) and expanding front-burner cooking plumes toward the narrow hood aperture. Hood flow is very ineffective at changing air direction well away from the hood; rather a hood functions by keeping plumes that make it to its aperture from escaping into the kitchen. Wolf should be embarrassed by their poser kitchen imagery on the linked page. A 15-inch depth hood will limit you to heavy cooking on the rear burners (assuming a wall mount), and even then the hood has to be wide enough.

If the hood metallic structure is to be hidden, then hood inserts are used in bump-out cabinetry in order to achieve a 24-plus-inch depth (as determined by cooktop size and placement), and in this case a desirable 42-inch width to overlap a 36-inch cooktop.

For a powerful cooktop in action, baffle filters are more suitable than mesh filters as shown in the Broan link. Mesh filters will loose effectiveness unless rigorously kept clean. They also have higher pressure loss if effective, and thus reduced flow rate for a given blower.

No air flows through the hood to the outside that hasn't been allowed into the house, and this inflowing air is called make-up air. Supplying it at low pressure loss, and conditioned where necessary, is an integral part of hood selection and integration into the kitchen when capture and containment require significant air flow.

Once the scope of the kitchen ventilation task is understood, we can support determination of the details.

kas

Kas - who should someone look for locally about this stuff? The last couple HVAC guys we spoke to (about a variety of things, we were getting quotes for adding a/c and replacing our boiler also) seemed not as clueful as I would like about this stuff. (A/C and heating, fine. Fancy kitchen stuff not so much.) Is that the right specialty to be talking to?

Thank you so very much for your information. It will definitely determine my choice for the hoodfan. It's actually not the first time Wolf has used "poser" pictures in their ads; I found the same kind of misleading image for their cooktop and matching sized oven below (ones there is an oven that fits perfectly understandable 36" cooktop).

Actually, you really saved my family from probably years of breathing the "burner combustion products". I will also make sure it has the baffle grill... Something I thought I didn't want because of the look, but here function needs to take center stage. Thank you again.