Effluent expands as it rises, so the 27-inch hood will have a better chance of capturing it. Larger hoods also allow some increase in their mounting height for taller cooks. (But keep in mind that to look over the range one has to bend, thereby reducing one's distance from the floor.) Position and type of hood lighting is also relevant, as a hot lamp just above one's head can be annoying. Larger hoods require more air flow in proportion to their aperture area (or at least in proportion to the area where the baffles are, depending on interior design details. And the make-up air has to support this flow. A roof fan or attic in-line fan will reduce local noise, and if space and resources permit, an in-line sound reducer/muffler/silencer will also help. One can converse in my kitchen next to my Wolf Pro Island hood with its 1500 cfm - rated roof fan at full power. I do have a Fantech silencer and have much of the ducting wrapped with vibration dampening sheets. Ultimately it is a trade in cost and appearance versus effectiveness and noise that each person has to make accounting for any limiting architectural factors. kas

The duct covers are available in 6, 12, 18 and 24" sizes. Contrary to what capecodcook says the Wolf covers are NOT telescopic, they are a welded, seamless design and are very high quality pieces that match the finish on your hood exactly. I have the Wolf Pro Island version and the duct cover is a gorgeous piece that is the structural mounting for the hood (and it should be gorgeous for the price!). Any Wolf dealer can order the duct cover you need. If they won't or can't, find another dealer that knows what they are doing.

I think the sizes you reference are height, mine was when I ordered the pro wall hood (not chimney style). Anyway, the height I needed was odd sized and the tallest extension they offered at the time was maybe 12 inches. What ever the limitations were, I remember I was going to need 2 pieces which meant a seam, then I was going to have to have a sheet metal shop cut one to size (one not enough, 2 too many...) and the pieces were expensive as sin. My Wolf distributor said they rarely used Wolf's rectangular SS chase's but rather had them custom made locally by a sheet metal shop for a fraction of the price. Interestingly enough, I checked into it and he was right. I had a local specialty sheet metal shop make one out of 18 gauge brushed SS and it matched perfectly! Actually, the protective film on the SS unit made locally was the same as on the hood that came from Wolf and ou could not tell it was not part of the Wolf package. I measured the width and depth needed and subtracted 1/8 inch to give a 1/16 inch (not noticeable) inset. You will never notice if the chase sits just inside the perimeter of the hood deminsions but will more likely notice it if hangs out even ever so slightly past or outside the finished hood perimeter. Then I had the height made to fit the exact height from the mounted hood to the ceiling. I also had (and this is VERY important) a 1/2 inch lip put on all of the "free" edges of the sheet metal enclosure to stiffen up the unit walls all of the way around. I spent less than half what Wolf's would have cost.

I am reading these posts with great interest as we moved into a house in September that has an island with Jenn-Air 4 burner gas cooktop and downdraft vent. We've always had electric but wanted gas in an island with an open floor plan so I could interact with our guests while cooking. The Jenn-Air system has many drawbacks. 1. I want/need 6 burners 2. Only one larger burner, two medium and one tiny. 3. Fan is LOUD on high and ineffective, even on high. 4. Fan IS EFFECTIVE at drawing the gas flame away from the pots/pans, thus greatly increasing cooking time. I want to replace this with a 6 burner gas cooktop that has enough space between the burners to use a couple of 12" saute pans plus a couple of 6-16qt pots and a couple of smaller pots. Based on the discussion above and the fact that I installed an 800CFM Broan under cabinet hood that barely kept up with the fumes in the old house, I think I'll want a 1200 or 1600 CFM blower (mounted in the attic to reduce noise in the kitchen). Problem is the master bath and walk-in closet is above the kitchen so I will have to shoehorn the ducting in the walk-in closet. I assume the extra run will eat some of the CFM. Does anyone have recommendations for a cooktop and vent/blower for this application, or links to sites with good product selection and design planning info? What about so-called "stacked" burners that are supposed to allow low simmering without compromising high output? If this post belongs in another category please let me know. I did a search but this seemed to be the discussion that most accurately covers my concerns. Thanks, Don