Ideally, you start with enough aperture to capture the rising expanding effluent. Then, having the aperture defined, calculate the CFM necessary to achieve a velocity equal to the rising effluent velocity. This would require 180 CFM per square foot of aperture for 3 ft/s rising effluent if there weren't other considerations. One of those is that with baffles, that velocity only needs to be achieved over about half the area due to the aero shape of the baffles and the flow around them. I didn't figure this out from computational fluid dynamics, but from the behavior of my Wolf Pro Island hood dealing with my induction wok which is offset towards one side (the induction cooktop is offset toward the other side). I expect mesh filters to behave similarly due to the mesh blocking at least half the area of the filter. While a fairly poor analog, if one thinks of the effluent as billiard balls in a zero gravity field hitting the hood filter, one can appreciate that conservation of momentum will cause those hitting a flat surface to bounce away from it such that the angle of exit equals the mirror image of the angle of arrival relative to the perpendicular to the surface that the effluent hits (just like light). The need is to change the momentum of the reflection by entraining the effluent into the hood air flow. Ideally, this is done as the effluent reaches the baffles/mesh and there is little bouncing reflection going on. You may appreciate that the flat surfaces of your nominal hood where there is no mesh will be regions where there will be effluent reflection. Some of that will be captured by the air flow which pulls in from a range of angles. In any case, for best operation, one wants the actual hood aperture to encompass all of the rising effluent and not make the aperture smaller just to get the local air velocity up. (A commercial kitchen hood is an example what is relatively optimal for maximizing capture while minimizing the cost of air handling.) But the bigger the hood, the more CFM needed, and the more make-up air CFM that has to replace the air in the kitchen. This not only adds the modest cost of ducting in MUA, but significant cost if the MUA has to be pushed by a fan and the fan has to be controlled to keep the house pressure in a narrow range. This can be more complex in some ways than large commercial buildings which can run MUA continuously and use pressure differential across a damper to control whether the fan output just circulates around in the fan loop or is pushed into the building. I think my previous post suggested that for the hood aperture you have, the actual CFM achieved will probably be enough. But imperfect capture and containment should expected from the hood aperture design due to the flat areas not being capture areas. kas

I have a recommendation for whole-house fans, and that is to go with the ones made by Triangle Engineering of Arkansas (made in the USA!). These things move more air than any other brand. As an example: the 36" belt-drive model sold at Lowes & Home Depot moves 6,900 CFM on its highest speed. The 36" one that Triangle makes moves 10,600 CFM. I just put one of these in last week and am so taken with it that I'm evangelizing for Triangle now. These things are much higher quality than the other brands too -- these are made with very heavy-gauge solid welded steel (as opposed to the thin, flimsy metal - often aluminum - that other brands use). They use a very solid motor made by Emerson, the best of the top three motor-making companies (the other two being Fasco and A.O. Smith). They come pre-framed on a wood frame for installation, AND they have sponge-rubber noise-dampening material between the fan and the frame, so they are much quieter than the other brands. Also, Triangle holds a patent on an automatic belt-tensioning system these things use, so you don't have to worry about getting the tension right when you install the fan (or in the years thereafter as the belt loosens up). Also, they come in more sizes than the other companies -- from 24" all the way up to 48" blade diameter (which moves a ridiculously whopping amount of air; no one else makes one that big). They're sold online at Southern Tool amongst other places that ship nationwide, so they're available wherever you live. Also, Triangle re-brands some of these as a private label for Dayton, which is the "store brand" of Grainger - so if you have a Grainger store near you (check your phone book or their website), you can buy one there. I will say this, though - Grainger/Dayton makes their own shutters, and those shutters are much better than the one Triangle makes. Triangle makes great fans, but crappy shutters. Luckily, they're sold separately -- so buy a Triangle fan and Dayton shutters; money can't buy better products. They also re-brand some for a company out in San Francisco called "Fanman" (a/k/a "Delta Breeze"). A word to the wise -- these fans move a lot of air, so make sure to install at least the recommended minimum amount of attic exhaust space (gable vents, soffit vents, roof vents, some combination thereof, whatever works for you) - if you don't have enough, the fan will operate at reduced capacity, and there will be a backpressure which will cause the shutters to rattle when the fan is in operation (any time you hear whole-house fan shutters rattling, you know there isn't enough exhaust space). Oh, and one other thing -- only buy a belt-drive whole-house fan, don't EVER buy a direct-drive model...the direct-drive models are at least five times louder, they sound like standing on an airport runway next to an old prop plane getting ready to take off. Several of the dedicated whole-house fan installing companies have chosen to use Triangle fans; that should tell you something. These companies want satisfied customers, so they use Triangle and only Triangle. Refer to http://www.trianglefans.com/wholehouse.html for more info Here is a link that might be useful: Triangle whole-house fans

@SparklingWater: Thank you so much for taking the time to post your thoughts. I have been checking in every hour to see if someone would respond. Yes, I definitely want to bring the cabinet above the hood forward and make it flush with the hood below. I thought it looked odd as well and asked the cabinet designer to modify it on the next plans. He also is planning on adding glass doors in the doors above. We are going to use 6" upper hood columns (instead of 3-4" columns as pictured) in that area as well. I also am replacing the faux "legs" under the rangetop with 6" "legs" that will have a pull out spice rack on each side. I think that will match well with the new 6" columns above. He has mentioned using furniture finishes to all the ends of all the cabinets although I did not ask him specifically about that area but will make sure to do so. We are using a counter depth fridge and that area you see will be covered. I hadn't thought about the depth of the cabinets in that area but will definitely ask (I hope the budget will allow it). My worry is that with the end bumped out, the middle pushed in, and then the one adjacent to the fridge bumped out it might look a little strange. Am I understanding you correctly? Appreciate your great feedback. I hope to post some updated pics in the middle of the week. If anyone else has any thoughts please let me know! Thanks and Happy Holidays! PS - Here's another view at that wall. You can see the furniture finish on the filler to the right of the fridge. Again, not sure on the left but I will ask. Sink wall/bar is open to the hearth room.

I have a master bedroom closet area along a wall that is bisected by the chimney chase of a fireplace on the floor below, making a his and hers pair of closets. This is a triple-wall metal chimney surrounded by firecode sheetrock on the inside, studs, insulation, and sheetrock on the outside, including an access panel. It eats up about 30 inches of closet length. For a 10-inch kitchen hood duct with significantly less fire and access restrictions, you would probably loose at most only 20 inches. Many things are possible if the house design is recursively adjusted to accommodate all of the requirements. Do not rush the construction until you are certain that you have met your needs; there will be enough surprises even after everything seems to be defined. If you go to equivalent rectangular duct, you may still need to bulge the wall or otherwise ensure that there is not too much duct restriction. Rectangular ducts of equal sectional area to round ducts have a bit more pressure loss per foot. This should not be your first consideration, however, because you can find a blower with a fan curve suitable for the duct design, even if the duct path is tortuous. As for all of your construction questions, I'll have to ponder them when I have time, if I can understand them. In any case, if cooking is an important part of your life, then ensure that the kitchen design and the ventilation design are given the attention and space that they deserve. Unfortunately, it seems that your framing plan is somewhat past the point of easy revision. For others reading this: Please, please, PLEASE look into and solve all of the kitchen issues before finalizing a design and signing a contract. Comments on your bullet questions: - ?run horizontal through floor joists? YES - ?use rectangular duct vent when necessary? YES - ?Is it allowed to run near/along side the gas dryer vent? Not aware of any restriction on the moist air vent (note dryer vent has to be metal also. However, care to allow access for both, and particularly for the dryer vent duct for cleaning, is important.) For gas effluent vent, that should be determined by consultation with the architect, code officer, or gas company tech. Note: given a gas dryer, we are now in the regime of not letting the differential air pressure at the dryer fall below 0.03 inches, w.c., and make-up air performance or sealing off the gas dryer from the kitchen air is another big part of the kitchen ventilation design. - Run down into the basement if it can't run up? YES, but less optimal than up - Exit through an exterior wall rather than roof? YES - Best to get it in the garage and up into the attic and then up out the roof? Don't know about best yet, but it is a valid option. - best to have the range on wall A or wall B (does it make a difference)? TBD. Kitchen layout should account for numerous factors, of which duct location is only one. - assume need to use remote or in-line blower with any plan given its non-traditional route? In most cases, an external blower with an in-line silencer will be the lowest noise solution. kas