I don't think it matters that you vent straight outside. The CFM specs of vent hoods basically assume you have a pretty straight run, with perhaps one 90.

Joe

250 isn't adequate - you should get a 600 CFM hood.

Listen to weissman......250 is like almost nothing. Game starts at 400....600 with variable control is viable consideration.

The cfm you need is one number; the cfm claimed by a vent hood manufacturer is a second number, and the cfm that a hood/blower installation actually pulls in the configuration in which it is installed is a third number. The third number is less than the second number. Your goal is to get the third number at least as large as the first number.

This usually requires the hood/blower combination to have a rated cfm significantly larger than that which is recommended for your cooktop. Many pages have been expended on this topic in this forum, and many more by researchers investigating adequate effluent capture. I'm installing trim today so I can't reprise this information.

Oven effluent is difficult to fully capture. Commercial systems called eyebrow hoods can be effective, but in a home such a collection system is usually impractical or unaesthetic. Ovens specified to broil with the door closed help, but when the meat is removed, there will be effluent released that escapes into the room.

I have a pair of registers on the ceiling above my double wall ovens connected to a dedicated roof upblast fan. These do not capture the rising effluent like a local hood would do. They do remove it from the air over time, just as a hood across the kitchen will eventually do. The registers are probably more efficient at removing air that rises to the ceiling than the hood over the cooktop.

The concentration of odor that escapes into the house air will be removed exponentially as a multiple of the time it takes to replace the volume of the house air at the cfm being removed (assuming uniform odor distribution and uniform room leakage.

kas

I had a 600 cfm Modern-Aire hood venting straight out in my old kitchen. It was barely enough for an underpowered gas cooktop which might have been an old Dacor, though it was mounted a bit high because of an existing window. I now have a 1200 cfm M-A hood, also venting out the wall, and mostly use induction. It's quite a bit more power than I need (they didn't have anything in between), but does an admirable job, rarely on full, often on lowest.

I don't think 250 cfm would be adequate for more than very basic things like a little boiling water, a low saute of a few vegetables, or eggs. For browning meats, boiling down stock, or frying, it doesn't seem adequate at all. Certainly not for pulling from the oven.

I have Gaggenau ovens, and I love them, but I sure do smell what's cooking! Perhaps the filters trap grease or other particulates, but not smells! On the rare occasions I make a bad smell (i.e., something spills and burns), I do find that my big, overpowered hood, which is about 6-8 feet away, does help. On top power. As in major suckage. Doesn't completely do it, but it helps. They used to make special hoods for wall ovens, but they don't seem to any more. I looked. I have a place to put one if I ever find one. :)

Thank you all for the advice. Turns out my research was a bit for naught, as we ran across the Zephyr Chang/Cache (with the hidden storage area) and my wife pretty well stopped my research there. I still have the choice of 290/600/1000CFMS, so it looks like we'll be going for the latter two (have to check my local MUA requirements).

Plllog, sounds like I'm trying to replicate a lot of your kitchen! Interesting comment about the smell out of the Gaggenau, as the catalytic converter is supposed to burn it off before it has a chance to escape. More marketing speak, I guess. That, and the side opening door, were the big selling features for me over the Wolf(E). I might just save the money and get me some rolling racks in the process. :)

Actually, you raised another question for me in your post. Apparently the Zephyr can be mounted anywhere from 24-36" from the counter. Where do most people mount it -- eye-level? above? below? We're fortunate in that my wife and I are both relatively the same height. I'd prefer not to clonk my head on the corners, but with this Zephyr we also have to make the allowance for reaching the storage area.

I personally would not go lower that the 600cfm. I had a 250 CFM for way too long with a fairly normal gas range and grease went everywhere excessively.

Our Kobe is only 24" above the stove deck, I wish it was higher:-) However hubby is 6'1", cooks quite a bit and has never whacked it with his head, I'm 5'4".

I think 30" is considered standard??

Consider drawing a scaled side view of the cooktop and hood, with the hood drawn on a separate piece of paper. Draw a stick figure representing the tallest cook at the position typically used, and draw eye-sight lines to the burners (or better to the likely sized pan edges). By moving the hood drawing down until the sight lines are interrupted, the lowest acceptable placement may be determined.

It may be of further value to evaluate how tall the pans can be before one has to get under the hood to look in. If this is too shallow, then the hood may need to be higher if head contact is predicted.

kas

I wonder if it's relevant to ask here about a glass (transparent) plate positioned at sneeze guard height. This won't interfere with arms a cooking and eyes a looking.

I agree. I think 30" is "standard". It's certainly the number most quoted as minimum height above gas. My previous hood was higher, but I don't remember exactly. It pulled pretty well, but I think it was above what was considered optimal height. Sounds like optimal for your Zephyr is probably 30" too, being that it's in the center of the range given.

About the filter, it's not that it fills the room with smells, mind you. There's a lot more when one opens the oven. It may just be that a certain amount of aroma escaping is inevitable. I never thought anything of it because I never believed that it could prevent all smells in the first place. The nasty burnt spills smell was mostly from opening the oven, if I remember right. No filter can prevent that. In fact, I can't say for sure that the odors are coming through the filters, and not let out when the door is open and then blown around by the vented air afterward.

Is all this venting to prevent smells? I have one of those recirculating hoods and am thinking of getting a venting one when I get my new Wolf cooktop (which specs does not require a venting hood). I just want one so that it takes the heat out in the summer when I'm doing all the fruits/veggies on the burners. How many CFMs does it require to get the heat out? Hang the smells; I like to smell what I'm cooking.

davidro1: If the sneeze guard is mounted outside the expanding plume zone, then it should aid capture. Otherwise, it could separate the plume into two parts, a captured part and a part to be eventually captured.

Sufficient hood overhang may require that the cook have very long arms to reach the pans on the back burners. Also, heavy pots may require that the cook get his shoulders somewhat over the pot to lift it. A flexible or swinging guard could accommodate these factors.

kas

I'm working on a pullout sneeze guard. Slide out. One part slides out, one part remains fixed to the wall. Without the fixed half, steam would escape out the back. So far, first version will be part Lexan part glass.

Thanks all.

Davidro1, I think kaseki's right in that a sneeze screen would be cumbersome (the only reason you tolerate it in a buffet is because you're not there for very long....and you're hungry!). A hinged screen might be best if you're going to install one.