@lithigin... It would be ok to vent through the roof and that is within our Residential Building Code. But, ours was never vented through the roof. The duct just ended inside the attic, near an existing attic vent to the outside. @lithigin and @artemis78... Well, I did not get to take a look at it in the attic. And, I would like to believe that it was a miscommunication, but they told me they ran the new vent duct into the attic next to but separate from existing ductwork so that it ended behind the attic vent to the outside. They said they also fastened a screen over the end of the duct. So, the unfortunate truth is that the cooktop vent ductwork was simply never truly vented to code. Whether or not it was vented to the outside, I guess, is in the semantics. The contractor and carpenter stand by their original work insisting that having the duct near the attic vent is appropriate as the attic vent goes to the outside. The dishonest part is that they led us to believe the cooktop duct had been vented to the outside TO CODE, when they knew it wasn't, even after my questioning them about it on several occasions. We did end up allowing them to correct the situation the way they suggested, through the outside wall. (At the time, I had asked them if a roof vent would be better, but they said it wasn't due to possible leak problems and my husband agreed with that.) So, now there is a separate grill vent directly below the existing attic vent. It works (the flaps lift up when the vent is turned on) and isn't particularly obvious or ugly from the street. I suppose once the new custom decorative chimney is up on the cooktop wall this won't seem nearly as bad as it does right now. (I have already found a fabricator and someone else to put it up --a recommendation from my real estate agent friend.) It's just that my trust was violated and it stings a lot right now. Instead of sitting around feeling sorry for myself, I am going to have to spend some time learning how to post pics (thank goodness for the instructions!) so everyone can see the finished results. Thank you for taking time to respond to my post.

Yay! I'm so happy reading things are getting fixed for you- I hope the finished product is done correctly and doesn't have the same issues. I didn't read every comment, so forgive me if you addressed this already- did anyone ever tell you exactly what caused this? I would want to know the cause to ensure the problem doesn't repeat itself. If it was poor craftsmanship - then I would want someone new fixing them. All I can say is, I have cheap builder grade cabinets that are almost 20 years old. I painted them five years ago (turned out great) and mine today look almost the same as they did five years ago. I have a couple hairline cracks but nothing like you pictured - so little oh me thinks - a kitchen like yours should be holding up way better than my old builder grade cabinets I painted myself. You had every right to be upset too. Again, I'm happy things are getting fixed. Post more pics when they get reinstalled :)

If it were my own home, I would have followed systems engineering process and analyzed the Hades out of the relevant subjects to be sure that what I ordered was all compatible, and then would have collected all components on site so final measurements could be made before ordering cabinets and placing electrical outlets. Perhaps needless to say, this has (and did have) the effect of greatly dragging out the reno. I would also have desperately tried to find a way to (a) use an exterior blower, and (b) find a place to put a silencer. And I would have to consider whether an 11 x 7 duct was too non-standard to contemplate. I have to assume for your home, eliasgrace, that your duct path is pretty fixed and there is no point in discussing variants. I think I would go with the squished 10-inch duct and then do the following: Tape all duct connections with approved tape See how well it works with more challenging plume generating cooking. Listen for how noisy it is Most importantly, not initially close up the access so that any vibration can be suppressed with techniques we can address later, and in any case, horizontal ducts should have a way to get into them if grease build up is detected, in this case possibly in noxious ways thru the cabinets. (Most of the time, residential grease not collected by the baffles is too sparse for grease drips out of the ducting, but plan ahead.) Some thinking about that now may save a lot of pain later.* You may wish to use a wood cover that is magnetically attached so it can be pulled off. If the blower is roof mounted, allowance should be made for having to upgrade it if flow rate is too low for full containment of the challenging plumes. If the blower is internal to the hood, then allowance for adding a roof blower is worth considering, although that could have electrical consequences. In spite of my comments above, I might be tempted to cut away the cabinets. However, this would change their structural strength without some additional structure that would have been much easier if added by the cabinet manufacturer. Replacing them would depend on their cost relative to the whole project. I'm not wearing your moccasins, so I fear that there is too little I know about all the details to assert that I know what's best. Last, let me note that your hood aperture is larger than my hood's 10 sq. ft. I use a 1500 CFM @ zero static pressure roof blower and 10-inch duct. It is adequate even without completed pressurized MUA (although it won't be if other exhaust fans are running so I still need it). Your actual specific flow rate (with all windows wide open) may turn out to be less than 90 CFM/sq. ft., and the impact on capture and containment will need to be closely observed. Fluid dynamics (applies to hood operation) is not linear or independent of the overall configuration, and general rules of thumb are merely ways of avoiding solving nearly intractable problems. What is your MUA approach? kas *Fantech makes some clamp unions that could perhaps simplify taking out a duct section.

OK, wok cooking: This requires the highest level of residential ventilation if you want all of the grease and water to be expelled instead of condensed on the interior. Start with capture. The plumes from pans expand as they rise. We believe that a good approximation for hood capture width is the cooktop width plus six inches. For a wall hood, the front-to-back opening should be wall to 3-inches past the cooktop (toward the cook). Lights and switch panels add to this, depending on how the hood is configured. Continue with containment. Given these aperture dimensions, modified by the reality of whatever products are actually available/affordable/aesthetic, and how the cooktop is installed in the counter, one computes the area of the hood entry area in square feet. Multiply by 90 CFM/sq. ft. (equivalent to an intake air velocity of 90 ft/min). This is the required or actual CFM. Multiply by 1.5 (if you don't want to do a complete analysis) to get blower-rated CFM, which is only valid when the blower is hanging in free air. Next is ducting: This is usually specified by the hood manufacturer, but the goal in cold climates is operation near 1000 ft/min, and otherwise in the range of 1000 to 2000 ft/min. This is given by duct sectional area divided by actual CFM. Don't forget noise: Best blower noise reduction is achieved by using a roof blower or in-line duct blower, with a silencer mounted between the blower and the hood. Silencers are about 4 inches larger in diameter than the duct, so silencer installation needs to be considered ab initio. Last, but really contemporaneous, is make-up air. MUA must be supplied such that the house internal pressure does not fall so far that combustion appliances, if any, are back-drafted. Some such devices, if not supplied with their own MUA, can be very sensitive. Even without such devices, one wants MUA pressure loss to be a small fraction of the cut-off pressure of the blower (top left of the fan curve). Review MUA related threads on this forum for more information.