If you look at the Modern-Aire site, they have several shapes where the front tapers at the top to the depth of an upper cabinet, and the sides are straight so as to butt up to, and cover, the yellow cabinet sides you mentioned. Their typical sizes are 18" and 30" high, but you could get a 24" custom one if your budget allows. Or you could get an 18" and have a box made for above it to cover that area and to which you could attach replacement moulding. The box could be made of either wood matching your moulding or sheetrock. Vent-a-hood has a stainless direct replacement if you decide to stick with the same size you now have. I'm attaching the link to the Modern-Aire page that shows their shapes. PS-10, PS-11, and PS-26 all have the characteristics I was talking about above. Here is a link that might be useful: Modern-Aire Hoods

Nadia I think you will really like it. I love that it slides out of the way, and is flush with my upper cabinets. I have a galley kitchen so this was absolutely perfect for me. Just be aware that it is light and not very heavy. The motor is heavy though,...if that makes sense. At first I was disappointed thinking it was flimsy, because I had nothing to compare it to. But it made the installation a breeze. There are three buttons on there that are not marked. I called the company and asked them how do I know which ones are which? The first one is 200 cfm, then 300 cfm then 600 cfm. There is also a timer button. The LED lights are really nice and light up my cooking surface very much. Also remember to turn the fan on before you start cooking, this really helps. One other thing I noticed is that when sautéing the surrounding area on my stove is cleaner,...bonus! For me the mesh will be a lot easier to clean than baffles. The mesh screens on these units pop out very easily. But this is a controversial subject on GW.

By interior air path, I meant that there would be a way for a cat or a butterfly to get from the vicinity of the air intake of the combustion appliance to the kitchen. If a combustion appliance has an air inlet path from outside, and a reasonably sealed exhaust path to the outside, and lives in an area that is more or less sealed off from the kitchen, I would call that isolated. Isolated combustion appliances would not be expected to backdraft due to the kitchen ventilation. All other such devices can backdraft when subjected to lowered house interior pressures, which is what happens when a big blower is used to pull air from the kitchen without sufficient MUA. As hinted at above, keeping the pressure drop low in the MUA path can be challenging, as large flow rates across even large filters can have a significant pressure drop.* So, unless the MUA has its own blower, filtering has to be minimal -- somewhere between sparrow restriction and mosquito restriction. Blower MUA systems have their own complexity (potentially a lot of it), as unlike many commercial operations where ventilation rates are held constant and the MUA can be tuned to a fixed rate, the hood blower likely has several speeds, there may be bathroom exhaust fans that can be on or off, and fireplaces can move a lot of air, but tolerate only a slight pressure drop to maintain sufficient draft. This is why I suggest where feasible that combustion appliances have some combination of their own MUA and some isolation from the kitchen (via a basement door that stays closed, say, or better, a closed room within the basement). My oil furnace has its own intake duct to the outside using a kit manufactured for this purpose. I'm not familiar with modern gas dryers or hot water heaters to be able to comment on equipment of this sort that might be available for them. In other words, minimizing the need to keep the house pressure difference to the outside within 0.03 inches may be a lot easier than incorporating a sufficiently sophisticated MUA system. There are some simple ways of controlling MUA that may appeal in some cases, and I'll try to get to that subject in the near future. kas

@opaone: your numbers, while still higher than my estimates, are at least within an order of magnitude, which in this business probably is reasonable correlation. I agree that this could rise to a significant concern with 10 people really cranking away in a poorly ventilated room. So we're on the same wavelength. @spurpura: you are correct in that I've not invested in air quality monitoring devices or hired PhD's to test my house. But my calculations are grounded in simple physics. The only assumption I have made is in the estimate of CO2 production during exercise, and that was from an academic sports physiology laboratory, authored by a PhD and published in a peer-reviewed journal. If you have figures showing that CO2 production during exercise is roughly 10 times higher than my estimate (which is what would be needed to support your observations), I'll await the citation. There are really only three possible scenarios: You are measuring local concentrations of CO2, presumably close to where you are exhaling. Your PhD consultants and their equipment are wrong. There's an exogenous unidentified source of CO2 infiltrating your exercise room. Enough of that dead end discussion. But...as to your original question, I think you're on the right track. As noted upthread, our 1200 cfm hood runs through a straight run of 10" duct, about 25' upwards, with an attic-mounted Fantech LD10 silencer and FKD10XL blower. It measures 60db (LCS weighted, ear level, roughly 4' from baffles) on high. So we hit the mark you are shooting for and I expect your setup will too. Good luck!