I'd like to try to convince you not to put the cooktop, especially gas, in front of a passthrough. It's very tempting for people to actually pass things through there, and that can be very dangerous. Knocked over pots are the least of it, burns and sleeves on fire are the worst.

If you put the cooktop to the side of the opening you'll be able to use a wall hood, have a backsplash, and still be able to see into the next room.

Oh Plllog! You have no imagination! I can think of far worse than mere burned sleeves and arms! :)

John, have you run your plan by the kitchen forum yet? I recommend it if you haven't. They (except maybe for me) are very sensible!

Have not run the design by the kitchen forum yet, but I should do so. I would have maybe 6 inches of wall above the counter before the opening so that provides some barrier for people's arms, etc.

I'm trying to preserve the location of the gas lines rather than moving them which is why i'd like to keep the cooktop where it is. I'll see if I can come up with a configuration that moves it slightly.

Moving or adding some gas line may shouldn't be that big of a deal.

Definitely avoid downdrafts, they just dont work (especially for the front burners). An overhead venthood is much better. As far as your concern with "blocking the view", there are plenty of companies that make slim models that keep the air clean without looking bulky. Here are a few I found while I was doing my own search:

Miele Lumen DA6290D
Kuppersbusch IKD122500EUL
Thermador Professional HPIN
Futuro Futuro Streamline ISSTREAMWHT
Franke Opus FDF367IXS

The higher the hood, the larger it has to be to collect the rising and expanding effluent. Also, the higher the hood the more the effluent is disturbed by drafts, including those from people moving about. Nonetheless, there are cases where this can work. I have seen ads for commercial kitchen ventilation where the entire ceiling is perforated metal and used as one giant collection surface.

kas

Kaseki - I agree. For example, commercial kitchens do not place range hoods 30" above the cooking surface, yet they place massive exhaust systems up near the ceiling.

My proposal is much the same. For a 30" cooktop with a distance of ~60" to the ceiling I would need roughly a 42" vent. This assumes steam/grease vapors expand 3" left or right for every 30" up.

Ellencrowe - Thanks for these suggestions. A nice slim island hood is not completely out of the question so I will look into the models you suggest.

I may be missing something, but it looks like the Broan L500k doesn't actually have any filters or baffles? It just exhausts the air out without filtering it at all? If so, if there is any length of ducting at all I would guess it would end up coated in grease, which would really not be good.

On the other hand, if it does have some kind of filter then it must be a pain to change, being up in the ceiling and all..

I jsut don't see how this works in the real world?

Commercial kitchens also get a lot of deadly grease fires.

And yes, what you have found is merely a fan. No filter, baffle, etc. This is just the part that moves air.

You can completely forget calculating the geometry of expanding effluent if you're cooking in front of a pass through. Room breezes will take your grease into the dining room, living room, family room, manscaping room or what have you well before they reach the ceiling.

Very valid points, there are no filters and baffles which would make this solution a grease nightmare after a year or two of use.

I guess i'm stuck with a conventional island hood or a telescoping downdraft...

For what it's worth...Best By Broan does have an in-ceiling option that includes filters. It requires a dropped ceiling of at least 13.75 inches, however, and only works with inline or external/remote blowers. I still don't see it working great in real world situations, since there is no contained capture area. Maybe if your kitchen was self-contained enough it could act as one big capture area it could work...

Here is a link that might be useful: Best By Broan Cirrus

A useful number for undisturbed air is +/- 22.5 degrees from the pan edges, although the angle varies with several factors.

The perforated ceiling systems address grease above the perforations with intense UV that breaks up the grease compounds into simpler relatively inert compounds.

One would want to build the kitchen from scratch or start with very high ceilings to consider such a system. One also has to deal with the ozone generated. I don't recall how that is addressed commercially.

kas

If the conditioned make up air you will need were dumped into the room where the pass-through leads, there would be less odor passing into that room.

Note that a 4 ft x 6 or more ft hood aperture mounted at 7 feet approximating a normal baffled commercial unit will force three inconvenient actions:

o Provision of enough vent cfm to keep the entrance velocity high enough at the hood aperture; i.e., to meet the requirements you can find on Greenheck's site for commercial cooking. You might be looking at 2000 cfm depending on cooktop size and what you cook.

o An equal amount of conditioned MUA and an attendant MUA control system

o A cooktop mounted far enough from the wall and pass-through to allow the expanding effluent to be captured and not passed through (at least in still air)

I'm not recommending this.

kas

We are also considering placing our cooktop infront of a pass-through which will be added to the wall between the dining room and the kitchen. I have been following the responses to your posting hoping to gain some insight. I am also concerned with using an island hood which will block a good portion of the pass-through space. What did you decide to do? What did you find regarding your options?