Of note - lines I drew in black are where the walls will be located (haven't gotten updated plans with these changes).

Do you know approximately how much space it'd take up in the closet? what would it look like? (anyone know of any pictures online or have themselves what something like this would look like)?

Is there an ideal spot in the closet for the ducts? (bottom of U - -> where exactly? bottom left corner of the WIC (wall sharing bed #3 WIC)?

Depending upon which way the second floor joists, run, can you just run it between the joists, parallel to them? Or go down, and run it through the basement?

As for 8" ductwork in a 2X6 wall- no. A 2X6 is actually only 5-1/2", and an 8" duct is- 8". It won't even fit in a 2X8 wall.

You posted this question on Aug 11th and I suggested two straight horizontal routes in dropped ceilings to an outside wall. Why couldn't they be used?

It is also possible to go across the garage ceiling or up through the garage to the roof (not my preference).

This is not a difficult installation. I can think of no reason to put a duct in a wall or a closet. Is there no designer involved?

I recommend no larger than a 400 CFM fan. To help you design the duct you must tell us what unit you have selected.

JDS - I wanted to know all possible options before I present them to the builder (trying to be as prepared as possible). We have not selected a hood yet b/c the builder told us we couldn't vent (I want this issue resolved before I go and pick one out) and i'm not going to get a re-circulating hood. I agree - hood would be no larger than 400CFM.

When you wrote - "2 straight horizontal routes in dropped ceilings to outside wall?" Can you draw it out in a rough sketch so I can see what you are referring to? (I'm very visual & yes, please dumb it down for me even more). With this design, would the range have to be on wall shared by kitchen/garage to do this? would the 2x4 wall have to be changed to a larger wall? how large? When you say dropped ceilings - is this the same as covering up the duct work with soffitts? when you say dropped ceilings, would the entire ceiling in the kitchen and near the sliders be 8 ft instead of 9 ft?

I appreciate your help. Thank you.

Here are the most obvious horizontal routes for the hood exhaust duct. None are too long; the longest I have installed is 40 ft. I can think of no reason the contractor would object to any of these routes.

Use rigid steel ducts secured with sheet metal screws terminating in an exterior metal hood with a back draft damper.

The ceilings only needs to be dropped where the duct cannot be put between the joists. When the duct must be below the joists the ceiling can be dropped in the entire space or just at the duct (soffit). With a 9 ft ceiling you have plenty of space to do that. If the builder is saying this is difficult he is pulling you leg; it couldn't be easier.

JDS: Thank you very much for those sketches and explanation, extremely helpful for me. Between the 3 choices you drew, is there one that is superior than the others? (i.e. option C b/c there are no 90 degree turns)? Is it better to try and stay in the house (option C) vs go in the garage (option b)?

Not sure if you can answer this with limited info, but assuming it would be non-pro gas range and no more than 400CFM hood,

1) what size duct should be used to be sure the fan/ventilation is still useful? (6'' or 8'')?

2) Any reason to need to use rectangular duct work or should try and use round the whole way?

3) Wall between kitchen/rear foyer is 2x4. What size wall is needed to accommodate the ducting?

4) In these scenarios, is a remote/external blower possible/recommended or no?

Lastly, I've read comments on trying to go up through the master bedroom closet and then through the roof. In your opinion, is this feasible or better than running horizontally and exiting through exterior wall? Or would they both produce approximately the same efficiency for the fan/ventilation?

OK. Straight above your stove is the location where the duct would go. Your Master Closet is more of a Backwards J than a U. If you were using lined paper, it would be where the bottom of the J sits on the line. Can you go straight out to the roof?

The duct size is determined by the manufacturer of the specific unit you select but it is likely to be 8" round which will fit in a 12" dropped ceiling or soffit. A round duct is cheaper and more efficient but in such a short run you could use a rectangular duct to raise the soffit/ceiling a bit.

The duct could rise vertically in cabinets and then run horizontally to the outside wall. Your kitchen designer can easily accommodate that standard detail. I've never seen a range exhaust duct installed in a wall.

I can think of no reason for a remote blower unless the sound of the fan at the highest speed (rarely used except when something is burned) is seriously objectionable. Most people run these fans at the lower speeds to reduce odors in other parts of the house. In my experience a remote fan is common in a commercial kitchen but very rare in a residential kitchen.

If you are going to use a fan larger than 400 CFM, you may have to provide an automatic make-up air system. that would only be worth it if you have a very large, high capacity, semi-pro gas range or the room is unusually large.

I would not terminate an exhaust at a roof if I could possibly do it at an exterior wall. It's not a matter of efficiency but avoiding roof leaks and snow & ice in northern climates. I try hard to avoid all unnecessary penetrations in a roof because wall penetrations are easier to waterproof.

I would do option C because it puts the termination away from windows and on a less important facade. Also, the ceilings/soffits can be easily built at 8 ft. from the floor and there would only be one 90 degree bend, and it might simplify the cabinet design. Be sure to get rid of the attic access hatch in the ceiling of the closet. You wouldn't be able to use it anyway and it is contrary to building code requirements.

JDS: Thank you for the roof penetration advice. I live in the South, so build-up of snow and ice is not really an issue for us.

Wonderful advice - thank you very much. Yes, anything we can do to avoid potential roof leaks due to snow/ice is welcomed. Spoke yesterday w/ GC and looks like it can be done (at a cost of course); Think I'm interested in option B vs C. Only question I have now is what size will the kitchen wall need to be to accommodate the 8'' duct? (it's currently a 2x4).

Thank you again!

Any particular recommendations for a simple but effective hood that is no larger than 400CFM? What kind should I be looking at given this particular set up (wall mount vs under cabinet)? Do slide-outs work well or stay away from those?

CFM is dependent on the cooking surface below and how many BTU's it can produce. 400 CFM is inadequate beyond a 30'' pro style range with only a couple of lit burners. With a pro style range, your costs don't stop at the range. You need a matching hood, and an adequate MUA system as well.

I don't understand why you would try to put the duct in a wall. Even if it were possible, what would be the purpose?

I don't like over the range hoods because I always hit my head on them. Making one thin and retractable would just compound the problem. I have two 30" ranges side by side each with a downdraft exhaust and rarely turn them on.