I have 1200 CFM above a 36" Bluestar rangetop and I rarely run it on high...if I do it's usually when I've burned something in the wall ovens, set off the smoke detectors, and I'm trying to clear the whole room of smoke.

I would think you'd be fine with 600 CFM.

Agree, with reservations. Ours is 1200 cfm and most of the time it runs at the lowest setting. However, when using the grill, oven, and several pots or when stir frying it's nice to be able to crank it up. A window is fine for MUA. Even though I don't use the full volume 90% of the time, its nice to have it.

I have a 36" radiant cooktop with a 650 hood. It's not the most powerful brand but its ok. On high, it pulls. I cooked 8 pieces of bacon the other day with the hood on low and I could smell bacon in the house the next days.

Also, I found I need make up air even with the hood on low. Otherwise it will suck smoky air down the chimney from across the house. So I crack the back door or a window in back. We have a picture window in an interior kitchen so no window to open directly. It's good to have one that opens I found.

As a hood, it's plenty powerful. I could see 1000 cfm with a Blue Star or Culinarian with powerful gas burners definitely. But for induction or radiant it isn't the same type of heat.

It's silly. You know what is required for you to use your range based on actually using the darn thing. Get what you want.

Unless you plan on changing your cooking style you're gonna be just fine with 650 CFM. And yeah I'd splurge on the 650. You don't have to actually turn it up that high you know!

(If it matters, I had a 600-650ish CFM GE monogram slideout over an induction cooktop for a few years and found it to be extremely acceptable.)

crl_:

1000 CFM over a 30" induction range in an old house kitchen? And no MUA? Really? Sounds almost like a case of "too much of a good thing is never enough." :>)

So, I'm with fori, rococogurl and the others on this.

However, I am interested in hearing the contractor's side. Has he/she explained any reasons for suggesting such a large capacity hood?

Is your contractor maybe thinking in terms of "resale value" arguments? (I.e., an argument like "YOU may not want or need one for YOUR range but everybody else in the neighborhood has them and any future buyers will want to put in a pro-style gas range" etc., etc.)

Or, when you said that "quieter would be nice" (as indicated in your post), is your contractor maybe thinking that high capacity fan in the hood hood can be run at low speeds, pulling, say, 350 cfm, when it will be a lot quieter than a smaller hood with a max capacity of 350cfm?

Also, I note that you are looking at a "slide out" rangehood. That suggests to me that your old house may have a smallish kitchen without room for a deep canopy venthood and that you are looking at a shallow vents. Believe me, I understand that calculus very well from working on the small kitchen in my own old house; I wound up with a 5" tall 650 cfm Zephyr because it fit where deep canopy models could not.

A good canopy (i.e., a vent with a real hood) over a stove helps make for efficient capture of steam and vaporous effluent and so requires less potent fans to be effective. With shallow, flat bottomed hoods (as well as OTR MWs and high-style flat-bottomed designer hoods) you have to depend almost entirely on the fans to collect the effluent vapor/ odor/steam. That means you need a lot more fan capacity to have any hope of effective capture. (For that reason, like Fori, I'd suggest going with the 650 cfm unit as long as you don't have a fireplace or woodstove in the house.)

Further limiting effectiveness, many slide-outs and other shallow and/or stylish venting units do not fully extend over the front burners on a range That is, many OTRS only project out 16 inches from the back wall. It's only a little more --- 18 to 22 inches -- on many other rangehoods. What that means as a practical matter is that a fair amount of the steam from a large stockpots of pasta water on the front burner can going up past the front of the hood onto your cabinets and walls. (At least with your Frigidaire induction range, you can bring the stockpot quickly to boil on a large front burner and then move it onto one of the smaller back-burners to maintain the boil; back there, a shallow hood or OTR will be capturing more of the steam.)

Of course, all this is speculation about what the contractor might have in mind. Can you get a clear rationale for the recommendation?

A hood/blower RATED flow rate of 135 cfm times the aperture area of the hood in square feet should for most configurations provide sufficient air velocity at the hood to successfully capture and contain 3 ft/s rising effluent from hot cooking.

Need for MUA depends on the presence of combustion appliances such as gas dryers, water heaters, and furnaces and whether they have their own MUA. The house pressure (difference with the outside) should not go more negative than 0.03 inches w.c. You may backdraft a fireplace with negative pressures also.

jwvideo covered the other aspects. A too small hood won't capture all of the rising effluent so while the value I gave will clear the hood, it won't immediately clear the kitchen if the hood doesn't overlap the rising and expanding effluent.

kas

"Is your contractor maybe thinking in terms of "resale value" arguments?"

I don't think that's the contractor's role. The contractor should worry about getting everything properly built, on schedule, up to code, with good craftsmanship and technically correct let the owner worry about resale.

I can see a contractor recommending a 1000 cfm hood if he's accustomed to installing Wolf or other gas ranges, especially large ones.

My hood is the same size as the top -- both are 36". Again, it clears sufficiently on medium and high and also will clear odors from the oven, which is about 18 inches away. I expect the capture isn't perfect without the overhang but no complaint. I also am able to use my Breville grill, my pancake griddle and my Oster steamer on the cooktop with the vent hood going and it does a good job. Messier with the grill when it's used open for burgers.

The one thing I can complain about is not having an operating window in the kitchen but it's my fault. We removed one and put in a picture window. I had no idea it would have that much impact. Our house was leaky and it was no different. We did full insulation and air ceiling but it's the same deal.

I will try to answer questions. I don't know our GC's rationale and that's a good point that I should just ask him to explain his thinking. I doubt he is thinking resale as we have very clear with him that we intend to live in this house for the long term. (And the neighborhood defintiely does not call for huge "professional" gas ranges.)

The capture point is a good one. The counter is that it's a small old kitchen. A big hood would dominate unreasonably, IMO. And I'm tall enough to bump my head on it too. So I think the slide out is a decent compromise.

We have a gas furnace that is located in the attic. I doubt it has it's own mua, though the attic is also leaky. We have a gas tankless water heater located on the exterior of the house. And we do have a wood burning fireplace--currently never used, but with very long range tentative plans to convert it to gas and use it.

The kitchen will have multiple operable windows (one of my main goals for this remodel is windows I can open in the kitchen).

Thanks everyone!

Oh, I forgot to say that I never made the quieter comment to our GC. I suggested the slide out vent we used in our last kitchen (the 300 cfm version I happily used with a gas range). He said, oh you need way more cfms, at least a thousand. Then he googled for a bit trying to find a slide out that he thought would be acceptable. Then he said we will have to work on that some more. And we moved on to the next topic.

rococogurl wrote>>> "'resale value" arguments?'I don't think that's the contractor's role"<<< Agreed, I thought it was self-evident but, since some of them overstep, it does bear stating. Anyway, looks like crl_ foreclosed the issue.

crl_:

MUA is just a way of providing outside air to appliances that might be drawing it from inside the house. Your furnace and waterheater are exterior to the living "envelope" and already should be getting outside air.

The fireplace will be the MUA concern if and when you start using it. Definitely want operating (and maintained) CO detectors. In your situation, MUA can be pretty simple if you need it.

If you had a gas range, I might agree with him. But not with induction. There is still that thing that larger is better as to noise if you always run it at a lower speed. IE, a 1000cfm unit running at 600cfm will be quieter than a 600cfm unit running at 600cfm. You're probably going to be content running the unit you like at 400cfm.

You can talk about MUA with him if you want to. It can be as simple as cutting a hole in the wall and using a barometric or electric damper, or far more complicated than you'ld ever want to pay for.

Thanks everyone! You have clarified and confirmed things for me. At our next meeting, I will ask why he is suggesting at least 1000 cfms. Unless his rationale changes my mind, I will let him know that I appreciate his input very much but we want to go with the highest cfm version of the slide out I had previously mentioned to him.

I purchased a 600 cfm ModernAire hood to go over an AG Wolf range. I placed the order early this month. I chose 600 based on Wolfs recommendation. This thread is causing me to wonder if I ordered the right size. I'll be using the oven to sear meat, stir fry in a Wok, and broil meat in the oven. Is 600 cfm enough?

Causing you to second guess yourself, eh?

First thing, a takeway from the above discussions is not to get fixated on CFM. Your Modernaire is a custom-built canopy hood, right? An actual hood helps a lot with collecting and directing the vaporous stuff to the baffles/filters and outside. You didn't buy a 48" range did you? How big is your stove?
Will you be running four woks on four burners at a time or just one wok on
one burner? Will you be searing/broiling dozens of steaks at a time or
just a few?
In the meantime, it may be reassuring (or not) to know that a lot of others have been down this same road before. Try a search on "wolf + all gas + rangehood + gardenweb."

I apologize for spreading self-doubt!