The stress on the roof beams should be least at their ends, so the amount of structural enhancement needed to allow a roof penetration for a horizontal duct near the hood height should be less than for penetrating higher on the roof. You might want to consult with an architect who can engineer a solution for that location. I can't help with any illustrations, although you might check out Soler & Palau's web site. I vaguely remember that they had some unusual duct runs shown there. kas

Boy- that's a good question. I'b probably go for the downdraft. It's out of the way until you need it. your eye will be drawn to that above island hood and maybe take away from other interesting things in your kitchen. And here's the big one. I have a stainless hood over my cooktop (not island) and I'm constantly wanting to degrease it. It always looks dusty on top, then you go to wipe it off & it's sticky, from grease or I don't know. I don't cook with a lot of grease. And don't even talk to me about the underside of hood. So I'm just saying that probably happens at every home, but I don't know if I'd want it out on display in the middle of my kitchen. Just my opinion. Not knowing the layout or look of your kitchen, I can't advise any different Good Luck Here is a link that might be useful: granite countertops

building2017 wrote: ... - What are the silencers I have read about and how do they work/would they work here? These are like giant truck mufflers, except designed for various diameter ducts. They have low pressure loss (forget the value but it is a lot less than baffles). Fantech is the source. - Any benefit re:sound to using two smaller liners instead of one big one and only using one at a time when using only one side of stove? Or is this magnifying the cost for no good reason other than sound? (Because I'm assuming I'd then have two runs up and out and two things on the roof because they wouldn't combine to avoid a turn and to ensure proper function? If only one side were run at a time, then MUA costs could be lower, but where code requires MUA, I am willing to bet a donut that the AHJ will demand an MUA system that can handle both at once. In theory, the sound reduction will be only 3 dB less. Also, when using the central burners, you will still need both systems for capture and containment. Well, I guess three things on the roof then with the MUA. While commercial systems mostly use roof MUA entry, and I use roof MUA entry, the options for residences are wide open and may include side of house entry, or entry into a basement that has an air path access to the kitchen.

In this -- expertly staged to look unstaged -- photo, one can see a Wolf Pro Island hood with a duct cover above it connected to an 8-ft ceiling. In this case, the 10-inch duct is centered in the cover. However, given enough ceiling height, the duct could be angled in the longitudinal direction of the hood. Whether this would help with the truss situation would depend on what direction the truss was relative to the hood. Also, it is possible to move the circular duct interface hole at the top of the hood in many cases, giving one more room for angulation or offset. Note that for best capture, the hood should be centered on the outline of the pans to be used on the burners, and not on the physical stove structure. This may be worth a few inches. In general, one would want to remove a truss by adding two equal trusses, one on each side of the duct penetration. This may not be possible without a serious amount of ceiling destruction, and possible cutting and rerouting of electrical, HVAC, DWV, and or water lines. If one calculated all the loads on the truss (may depend on walls, water beds, etc.), then a number of microlam beams might do, carrying the truss loads around where the truss is broken. I wouldn't consider this without having an architect involved, unless I had done all the calculations and knew what the loads were and what the safety margin was. And before I did that I would look into a custom hood in which the duct was offset from the hood entry aperture in the transverse direction. Some commercial hoods are of this type and the design can be carried over to a custom residential hood. And, before I did any of that I would seriously look at the kitchen plan to see if I could move the hood rather than ravage an existing structure.