Exposed ductwork in an older home can be quite charming. It gives it an evolved over time feel. Or, it can be hidden within the cabinets. Either way, it will have to go straight up and then left to go out of the building. I'd do at least an 8" duct, as that gives you more versatility than a 6" duct. 6" limits the possibilities down the road. Doing 8" now instead of 6" won't increase the cost but a couple of dollars, and you could possibly do a higher BTU stove and vent at some point if that interests you because the infrastructure would already be done. [Modern Kitchen[(https://www.houzz.com/photos/modern-kitchen-ideas-phbr1-bp~t_709~s_2105) by Dallas Architects & Designers Domiteaux + Baggett Architects, PLLC [Modern Kitchen[(https://www.houzz.com/photos/modern-kitchen-ideas-phbr1-bp~t_709~s_2105) by Fairfax Kitchen & Bath Designers Kleppinger Design Group, Inc. [Contemporary Kitchen[(https://www.houzz.com/photos/contemporary-kitchen-ideas-phbr1-bp~t_709~s_2103) by Chicago Kitchen & Bath Designers Steve Bailey - Amish Custom Kitchens [Eclectic Kitchen[(https://www.houzz.com/photos/eclectic-kitchen-ideas-phbr1-bp~t_709~s_2104) by Denver Interior Designers & Decorators Momoko Morton

The hood's width at 6" wider than the cooktop is ideal, but many people have the hood the same width as the cooktop, and it's fine. Often people don't want to give up the 6" of upper cabinets, or cannot, because the cabinets are already there. If you have the space for a 42" wide hood, it would be the better choice, but is not an absolute requirement. The thinking on hoods has moved somewhat from emphasizing the width of 6" wider, to more emphasis on the depth of the hood front-to-back. Many hoods sold these days are only 20" front-to-back, leaving the front burners uncovered. That is more of an issue than ensuring extra width on the hood. Find a hood that is close to 24" front-to-back if you can. The height of the hood is ideally 30-36" between the top of the cooktop and the bottom of the hood. If you install higher than that, you are allowing too much space for smoke and grease to escape and float around the kitchen. Go lower than that and your cooking area will feel cramped. I want to reiterate what Stan Z said about the correct ducting. You can have the best hood in the universe, but if your duct diameter is too small, your hood performance will be constrained. Most hoods require 8" or 10" diameter - the specs will say which. You can find hoods with specs for 6" diameter, but those hoods will be noisy, as air is pulled through a more narrow space. 600 cfms is usually enough for most people with a 36" width cooktop. Underpowering the hood is a mistake - you will have spent all that money on the hood, and it will be inadequate from the get-go. If you are thinking about going with more than 600 cfms, the advantage would be that you can run the hood on a lower speed setting most of the time, which will be quieter. The disadvantage of more than 600 cfms is that may require make-up air depending on your locality, building code, and how tight your house is.

We installed a similar vent-a-hood (48" with 900 cfm triple blower fan), and you will definitely need to do some work on your ceiling. We installed in a 1 story house, and we were using the vent-a-hood liner, not the stand-alone housing. They built a decorative plenum above the range (cathedral ceiling) and recessed the hood liner up into the plenum. The ducting then connected straight up to a vent through the attic and to the roof. I believe that the unit you picked is actually two 600 cfm dual fans that each require an 8 inch duct. You can then use a duct combiner (about 17" tall) to bring them together into a single 12" duct. The centerline of each 8" duct is about 11" away from the centerline of the hood. Do you plan to build any type of decorative plenum/trim above the hood to get the hood to the correct height over the range? If so, that could give you some working room for ducting options. The option I am considering is whether you could use two 8" ducts, but jog one over so you could run them between two adjacent floor joists or one above the other (hidden by a plenum). It still requires removing quite a bit of ceiling, but will fit well with typical joist spacing. The other choice is to run each 8" duct a different direction along the joist, but you will probably run into a load bearing wall in one of the directions. The other option is to look at the floor above to see if you could route the 12" duct (or two 8" ducts) vertically. If you could grab space from a closet or the corner of a room, you could run the duct(s) straight up and out the roof. The code requirement for make-up air when a fan moves more than 450 cfm is a relatively new requirement. If your city follows code, you will have an added expense for an automatic make-up air vent that opens when you run the exhaust. However, I installed a 600 cfm fan during renovation of my current house in 2014 and the inspector never even mentioned make-up air, so YMMV. Removing and replacing sheetrock ceilings is messy, and looks bad when its out, but its really very straightforward construction work that does not require a licensed professional. I would not get very concerned about how much ceiling has to come out. Bruce

"Can we attach flexible piping to the 6" duct" DANGER. You cannot install flexible pipe for a cooktop exhaust. Flexible duct is prohibited by Building Code. It is a fire hazard. Here is why: the duct must be smooth so that grease particles do not get trapped and cause a fire. If you have grease particles in the crannies of flexible duct above your hood, and your cooking has even the tiniest flare-up, that grease will catch, the fire will whoosh up the duct assisted by the pull of the air flow, and then spread across your walls, and ultimately your house. You may be thinking "this isn't likely for us". Except that according to the Insurance Information Institute, a home fire occurs every 87 seconds in the U.S., and 50% of all home fires are caused by cooking fires. So just use rigid metal duct, and an elbow if you need to turn it in a different direction. "Will it affect the venting power?" What will affect the venting power is the 6" duct size you specified. The duct needs to be a 8" or 10" diameter for good air flow to pull up the smoke and grease. People get by on a 6" duct size because their homes already have the 6" duct behind walls so they are stuck with it. But if you are installing new duct - which it sounds like you are - you have the opportunity to install 8" or 10" duct. It does not make much sense to spend money on a new hood, but curtail its air flow from the getgo with a 6" duct. "induction doesn't cause as much smoke." Not true. The smoke and grease is a function of what you are cooking, not the energy source. If you are cooking bacon, frying a hamburger, or stir frying, the smoke and grease are the same whether using induction or a gas cooktop. If your family is vegetarian, or you never use the cooktop for frying , then it makes sense to say your cooking does not cause as much smoke, but it's not because of an induction cooktop. I think it's best to budget for smoke and grease, and if you don't often generate it, you can turn the hood fan to a lower speed, but on the occasion you are cooking a smokey item, you have enough ventilation not to set off the smoke alarm. Not what you asked, but essential measurements: - width of the hood is ideally 6" wider than the cooktop, so your hood should be 42" wide. - depth of the hood front-to-back should be 24" in order to cover the front burners. This is where a lot of cabinet hood surrounds fall short. You can get away with a 22" depth, but not less, or you would have spent all the money and effort for a hood that does not even cover your front burners. - Distance from cooktop to bottom of hood shoud be between 30"-36". Shorter than that and you will have a cramped feeling when cooking. Higher than that and you are giving the smoke and grease too much opportunity to escape.