The electrician finally came today and hooked up our power. And then they turned on the A/C for the first time since our fire in March '09. I couldn't have worked a minute longer in that house - it's July in Houston and man is it hot. Now that the A/C is on we have to wait a few days and then the marmoleum installer will come and do a moisture test on our slab. At that point we'll be ready for the kitchen floor to go in, and then I suppose we'll follow up with the Thermador 48" built-in fridge. The cooktop, wine cooler, wall ovens and warming drawer are boxed up in the L/R, so they could go in (I guess we need the plumber for the gas cooktop, but the electrician can do the rest). We'd hoped to move in this week, but I think we still have a week or so of work to do. So hopefully next week. Because if we are not in next week then I am going to have to cancel or significantly revise my planned vacation and someone is going to get a serious lecture. Our builder said on June 9 that we were 4 weeks away...hah hah hah. That was before his electrical sub stopped returning his calls. GRRR! Time for a glass of wine.

We need a lot more information, I think. Ideally, I would suggest, rip out your central AC system and replace it with a minisplit heatpump. Takes up less space, much more responsive, much more energy efficient, and neatly solves your problem. Unfortunately, it does incur a big upfront cost. So, this might not be what you want to do. The next question is, what is above your kitchen? Can you vent to the roof? If so, you might be able to have an S-shaped section of vent pipe that navigates past your AC ducts. Or you might be able to push your AC ducts into the ceiling joists above, and then there are all sorts of other ways to either route the vent to the side of the house or past the AC duct. If you can run the AC duct in the ceiling, that would also allow you to move it away from the wall. Of course, a bigger soffit would do the same job, but I can't tell whether that would look OK. It might also be possible to place the stove somewhere else. Or, if you are really desperate, you could get a VentAHood recirculation system. It's not as good as a properly venting hood. But of all the recirculating hoods, this is the only one that actually does work, as it has extensive filtering built-in. There are so many possibilities. But it is really hard to tell without seeing more details and without knowing your budget.

All of this is backwards! To determine requirements, one starts with the cooktop size and based on cooking plume expansion determines the hood entry aperture (capture area) size. From this the flow rate (CFM) is determined, and thence the duct diameter. Also, based on the flow rate and local ordinances, personal preferences, house architecture, and exterior environment, one establishes the requirements for the make-up air system. When requirements are established the hunt for systems or components of systems can proceed. Details of the requirements process can be found in many "hood" and "MUA" threads on this forum. Absorbing the first dozen or so pages of Greenheck's commercial perspective on this topic may be helpful. See: http://www.greenheck.com/media/pdf/otherinfo/KVSApplDesign_catalog.pdf

@sarah hossain I'm not an expert like @kaseki is on vent hoods, but here's my best try at answering your questions: Is makeup air (MUA) absolutely necessary if your house isn't tight? Well, my house was built in 1985 before more modern insulation methods were used and isn't tight at all, but I still get better exhaust through bathroom fans when I open a window, and those are only 150 CFM. When you get into 300 CFM or higher for a vent hood, you'll probably want to open a window or door to help with airflow if you don't have MUA regardless of how leaky your house is. Lack of MUA whether ducted or via something like opening a window will actually restrict the effectiveness of your blower at any speed. I don't have MUA and am about to install a ducted hood like you want to do. I chose a Wolf hood for the premium under-hood capture space with tilted baffles and a 300 CFM blower. In my city, I am required to keep the CFM of my blower 400 or less unless I have makeup air. This is very common because it complies with the International Residential Code (IRC) and helps prevent dangerous gasses from being pulled from the water heater, fireplace or other appliances into your breathing space when a high-CFM blower is being operated. If you live outside city limits, you won't necessarily need to abide by any code, but I wouldn't put anything more than a 600 CFM blower in a house without MUA for safety reasons. Most cities will require a permit for inspecting the new ducting work, and the inspector is usually going to also be checking that your new hood meets whatever code has been established. In northern climates where homes are built tighter, some cities have adopted a 300 CFM limit without MUA. Other cities have made exceptions to the IRC and allow up to 600 CFM without MUA. The requirements could be anywhere in between, but I've never seen mention of any city's code that exceeds 600 CFM for any reason without MUA. Keep in mind that while ideally you would want to open a window if you don't have MUA, that isn't always going to happen due to convenience or outdoor temperatures year-round. Does a large home and open floor plan reduce my need for a make-up air system? Having a large home such as yours as well as an open floor plan probably does help with exhaust issues if you don't have a MUA system. However, at some point if you are running your blower at the highest speed setting for a long period of time, you will need some way to provide make-up air even if it is through opening a window. A blower rated for 600 CFM won't provide that much actual exhaust if the interior airflow is restricted due to lack of make-up air. Limited options for ducting out of a centralized kitchen. It sounds as if you're bounded on all sides with that kitchen. Staircase to the right, bedroom upstairs, sun room on another side, all of this leads me to wonder if you've considered a totally different option which I'll try to explain. In Germany and some other European places where air efficiency is critical, it is actually more common to install a good recirculating vent hood with filters and then a heated air exchange system about 6 feet away from the hood that helps to exchange air with the outside. This helps to preserve the heating/cooling in your home since the air that is put back inside the house is pre-heated, and it actually does a pretty effective job of removing the things you want removed from the kitchen airspace. I found this early in my search on hoods and don't know if I can re-find the links where I read about it, but it might be a really good option in your case. You could keep the range where it is, install an island vent hood with a deep under-hood capture area and replaceable filters and washable baffles. Then install this other air-exchange system somewhere else, and you may have what you want. If I can locate the link to more info, I'll try to post again here later.