Thank you all for the replies! Glad to know that you guys think a couple of inches is not a big deal. Good to know that baffle filters are good for grease. What's wrong with oil cups? All things being equal baffle definitely looks better for sure. What do you think of a smaller thinner hood with mesh filter, like the 400CFM Bosch DUH36252UC? Yes I am also concerned about field of view. The height of the future range is a standard size (36 inch). Our options are limited. Really don't want another downdraft -- the only downdraft range is Jenn-Air, expensive and also terrible reviews for its reliability. The only other option is a low profile hood with sliding glass visor. But that will eat up the cabinet above the range in kitchen already tight for space. :(

The canopy wants to trap the rising smoke/vapor/greaseparticles, which we call "effluent" for short, and the effluent column expands as it rises. What that means is that as you increase the vertical gap between the stovetop and canopy, you need a wider and deeper canopy to get the same amount of effluent capture. You may also need a little more cfm. If not, as Momto says, some of the effluent escapes. How worried you are about that will depend partly on your cooking. If you do a lot of wok cooking and meat-searing, I'd be more worried about effluent capture. Also how close the kitchen is to the rest of the house, how sensitive people are to odors, how often you want to wash your walls etc. A lot of folks go for 30" or less vertical distance to get good capture, and say that they soon learn not to bump their heads. I went for a canopy just above my 6' height, but with 12" overlap on either side of the cooktop and a 9-inch bump-out from the wall. You will find *lots* of discussions of hood height if you search the appliances forum, as well as cfm and other issues. For example, makeup air is essential if you are venting a 60" Wolf, and will have a lot to do with how effective your ventilation is. This is new to a lot of people...

The standard walkway range between work surfaces is anywhere from 3 ft. to 5 ft. Three feet is not enough for two people to pass each other, so if you have more than one person using the kitchen at once, definitely don't do the minimum. If you are the sole cook and value efficiency in your kitchen above all else, you might find 3 ft. ideal. It means you can just turn around, rather than turning and then walking to use your island. Five feet is very comfortable for people passing each other, so if you often have a crowded kitchen, that can be nice. However, I have often heard on here that various people feel that five feet puts the island just a step or two farther than feels natural to walk to get to the island. The sweet spot for the majority of people seems closer to 4 ft., but the exact distance seems to be personal thing. Your best bet is definitely to mock up various distances in your existing kitchen and see what feels the most natural to you.

The specifications on my GE range are identical to the NKBA guideline that Benjesbride posted: 30" min. to a cabinet or other combustible surface; 24" min. when the "bottom of wood or metal cabinet is protected by no less than 1/4” (6.4 mm) thick flame-retardant millboard covered with no less than No. 28 MSG sheet metal (.015” [.38 mm] thick), .015” (.38 mm) thick stainless steel, .025” (0.64 mm) aluminum or .020” (0.5 mm) copper." Say that three times fast. :) Just to be double sure, I called GE customer service to confirm that a metal vent hood in fact falls under the 24" guideline. It does. Our Zephyr hood specifies the same numbers, 24" to 32" over the cooking surface, if I recall correctly.