Well THANK you Weissman, Breezy and Madeline for your strength on this! I'm recharged to have it done properly, according to Code. DH is on board with this too. We do not have a GC so will have to take the stand ourselves. Madeline, I was unaware of Coburn's. The closest one is in Athens TX, about 1.5 hours away, but I'm going to call them tomorrow. Thanks so much for sharing that. At least mine does not go up into the attic -- it is all self-contained in the hood itself, and goes straight out the wall behind the hood. But your point is well-taken -- one squish or kink in the flexduct and that can ruin the whole reason for having it. One more question for you: I see his problem. There is no access panel, so how is he supposed to get his hands up there to connect the unit to the rigid duct after he has pushed it up into the wood hood? Thus he's saying he needs the flexduct to dangle down... BUT, don't you think that with precise measurements and good care, he could arrange and position the rigid pipe so that it mates up perfectly with the unit when he pushes it up there?? Or should the cabinetmaker have made some kind of access panel on the front of the hood? I see a lot of pics of hoods that definitely don't look like they have access panels. I've just spoken to our plumber about this, who's coming tomorrow to hook up the sink etc., and he thinks the above is do-able (mate the two pipes as the unit is being pushed up and positioned.) What's your experience on this? Thank you again, I'm so glad I asked.

Sorry if I was unclear, but the silencer removes noise that is beyond the silencer relative to the listener. So, not that it would matter, but hood baffle noise would be partially silenced when listening on the roof. Relative to the cook in the kitchen, the silencer removes noise beyond it. So, hood baffle noise and local duct noise and local hood interior transition noise won't be affected by the silencer when listening at the cooktop, but duct noise on the roof side of the silencer and most importantly blade tip turbulence noise from the roof blower or the in-line blower that is past the silencer (relative to the hood) will be attenuated when listening at the cooktop. The blower noise is typically the loudest, so the silencer is important to minimizing noise. (It is worth pointing out as I think I did sometime in the past that blade tip turbulence noise dominates baffle noise given well designed baffles. I only have personal experience with my Wolf/Independent hood, so it is possible that a particular baffle design could be noisier than a particular blower design.) So the silencer should be as near as feasible to the hood (past any dampers), and the motor closer to the roof or on the roof. A duct that passes heated rooms should be insulated from the rooms passed, and possibly partially coated with damping material (I use automotive sheet metal dampener sheets). A damper is needed at the hood (probably part of the hood) and another should be at the roof. The Wolf/Broan low profile blower I have has its own damper which opens upon flow. Abbaka and Broan blowers look similar and appear to use the same approach. An upblast or downblast quasi-commercial blower and housing design may need a conventional damper just below it. Dampers should be checked for function without hanging up on errant screws before workmen can escape the project. A straight run will have minimal duct bend turbulence noise (caused by flow separation, perhaps). It may or may not make adding a silencer inconvenient, architecturally. kas

All of the above may be true, but are not in themselves totally limiting. In general, there is always a blower that will move a desired air flow volumetric rate through a given duct, but one might not want to operate it, listen to it, or pay for it. But in this case we are on the margin, and feasibility is not prohibited using conventional devices. For example, I have a Wolf/Broan 1500 CFM rated roof-mounted blower operating with a 10-inch duct, and given various estimated pressure losses, expect that it moves 900 - 1000 CFM. A 1000 CFM rated typical hood blower, no matter how large the duct, at a minimum will be significantly restricted by the hood baffles, and at a maximum by any added MUA pressure losses, and would be unlikely to move more than 700 CFM in use with a hood. An 8-inch duct has a sectional area of 64% of that of a 10-inch duct, so the pressure losses operating at 67% through an 8-inch duct of the air flow rate through a 10-inch duct will be similar. In general, one wants to select a blower having a fan curve that supports the desired flow rate at the pressure loss that one estimates is present. Without my looking up the specified hood, let us assume that its entrance aperture is 42 x 27 inches or just under 8 sq. ft. This calls for 8 x 90 CFM/sq. ft. or 720 actual CFM. A typical 1000 CFM blower may achieve this with a 8-inch duct, and one certainly can check the assumptions against blower fan curves (where available) to either ensure adequacy, or at least force the MUA system to be active and not cause significant pressure loss. Note that this doesn't violate your appliance guy's opinion about duct flow rates, although I am sure that his view is based on typical in-hood blowers. If you have the room in some part of the duct path, then including a silencer will help reduce noise back at the hood for only a small added pressure loss. In any case, numerous commercial kitchen ventilation blowers can be found that will pull 720 CFM against any pressure loss likely from a well designed hood/MUA setup. It is quieter to move a given flow rate when the fan blades are large and moving slowly than small and moving quickly, as the latter generates more high frequency noise from turbulence. Induction motors can be controlled by rheostat adjusted phase circuits, and these can be put into hoods. My Wolf hood has such a control, and now the technology allows for it to be performed with better techniques at low cost. These comments are meant to touch on most of your questions, but feel free to delve deeper as needed. kas

The curved glass canopy is what makes this all a little more complicated. If you fabricate a new cover, it has to trace the same shape. That's of course entirely doable. A laser cutter or a water jet would easily be able to cut this shape. But you need to pay somebody to program the shape; and they might need access to the hood to take really precise measurements. Also, you need to pay for the length of the cut. That's how billing for these things usually works out. The good news is that the cover doesn't look structural at all. You can make it from relatively thin material. That drives down the material cost, and it substantially drives down the manufacturing cost. Cutting thin materials is a lot easier than cutting thick ones. My guess is that you'd still be looking at several hundred dollars to make a custom cover including the bottom cut, some tabs for the screws, and the openings for the exhaust. In the big scheme of things of a full kitchen remodel, that's just the expected cost of overages. But compared to the cost of the hood, that's a painful extra charge. When all is said and done, it'll look great though.