Could you post a picture of the space with a bit of an idea of your style. You also need what CFM is needed for your cooktop. What kind of cooking top gas or induction.

Great questions. The space was just demo-d so I don't think a photo will help, but I'm looking for a simple "modern farmhouse" type style, shaker cabinets, stone or marble counters. Want a simple stainless hood. and like both the square "T" style and the pyramid ones. Here's one example - https://www.build.com/kobe-isx2136sqb-2/s1430060?uid=3360744

Cooking over electric, not gas, but we're a high cooking household. Duct run is straight out about 10-12' and I'm thinking somewhere between 300-900 CFM will be fine.

If this hood is intended to function as a means of capturing and containing cooking effluent, then requirements should precede selection.

Req. 1: Capture requires the hood to overlap the cooking surfaces by enough to encompass the rising and expanding cooking plumes. At the preferred height, the hood entrance aperture should be at least 10 degrees from the vertical outside the limits of the relevant pan sizes to be used. This is 5 inches at 30-inches height, 6 inches at 36-inches height. These values are smaller if measuring from the the boundaries of the range or cooktop instead of the pans. Hence the rule-of-thumb of 6 inches wider than the cooktop, and at least 24 inches of aperture for island hoods. Drafty areas need larger hoods over islands.

Req. 2: Containment requires sufficient air flow that all that is captured is pulled through the baffles and exhausted from the house (or filtered and recycled). Typically, 90 ft/min == 90 CFM/sq. ft. is sufficient. Somewhat less may be sufficient for nominal induction cooking where high temperature (near smoke point) grease is not being generated. Velocity times aperture area equals volumetric flow rate (CFM).

Req. 3: The relationship of actual flow rate to blower rated flow rate depends on the blower's fan curve and pressure losses in the system loop: cooktop to outside to inside to cooktop. Lacking any other data, a multiplier of 1.5 applied to the calculation of Req. 2 wil be sufficient.

Req. 4: Make up air will be needed, either incidental, passive, or active depending on factors not yet specified.

Req. 5: Duct size should be sufficient to not exceed 2000 ft/min in the duct at full power, with preference to be closer to 1000 ft/min if feasible, particularly if some of the duct is exposed to cold.

This should do as a starter, from which selections can be made consistent with aesthetics and cost. Note that only two of performance, aesthetics, and low cost can be achieved, and generally trades among them will be necessary unless cost is no object.

Req. 1: Capture requires the hood to overlap the cooking surfaces

Yes, going for a 36" hood over a 30" stove, and as you note, pan size and placement will be set within the 30" wide cooktop.

Req. 2: Containment requires sufficient air flow... Typically, 90 ft/min == 90 CFM/sq. ft. is sufficient.

Not sure I'm exactly following your math here (90 CFM for each square foot of room in the kitchen would mean you'd need a 103,680 CFM fan in a 12'x12' kitchen with an 8' ceiling?) but I've done enough reading and research to have a general sense of what CFM ratings mean and suspect that the 300-900 CFM range I suggested will be more or less ok here. If I'm missing something, I'm open to learning more.

Req. 3: The relationship of actual flow rate to blower rated flow rate depends on the blower's fan curve and pressure losses in the system loop: cooktop to outside to inside to cooktop.

Exhaust will go up into the ceiling, and then take a 90 deg turn into a rigid 6" duct that runs about 11' between joists and vents out through the wall to outside.

Req. 4: Make up air will be needed, either incidental, passive, or active depending on factors not yet specified.

I live in a 100+ year old house and while I've done some air sealing, I think it's still leaky enough to allow for incidental / passive makeup air. There's no combustion of any kind in this space so I'm not too concerned about backdraft on chimneys or gas heating systems or anything like that.

Req. 5: Duct size should be sufficient to not exceed 2000 ft/min in the duct at full power, with preference to be closer to 1000 ft/min if feasible, particularly if some of the duct is exposed to cold.

Duct run is entirely inside the conditioned envelope of the house until it exits the wall. 6" round rigid metal duct, running about 11' horizontally in joists between the kitchen ceiling and the floor of the living space above.

@kaseki - I wonder if you're thinking of the HVI guidelines posted here?

https://www.hvi.org/resources/publications/home-ventilation-guide-articles/how-much-ventilation-do-i-need/

They recommend 150 CFM per linear foot of range - so with a 30" wide range (2.5') I'd want 375 CFM.

My two current top contenders are from ZLine and Kobe, but I'm looking for feedback on those choices and very open to other suggestions.

Here's the ZLine: https://www.zlinekitchen.com/ke2i

And the Kobe: https://www.koberangehoods.com/product/isx21-sqb-2-series/

And I'm liking the look of this lower-profile pyramid type hood on this one from Sirius, but can't find as many specs on the company and would love to keep the budget under $1,000.

http://www.siriuscappe.com/usa/island_series/island_hoods_siu3.htm

There’s nothing “farmhouse” about the Kobe, Z Line, or the Sirius hoods. Modern, yes. Farmhouse, no.

Are you more concerned about price, or efficiency and quietness of a hood? For under $1,000, I doubt you’ll be able to get anything close to quiet, when the fan is on medium or high.

Listen to @kaseki. He/she really knows their ventilation “stuff.”

Is there anyplace else in the kitchen you could put your rangetop? Most pros are quite negative about having one in an island.

There are people here who are great at figuring out the best kitchen layout. Post a sketch of the room, with dimensions, to help them help you. Are you working with a KD?

Fair enough - I'd say I'm looking for modern hoods and appliances and the farmhouse part of things can come through in other ways.

In terms of priorities, you know, I'm human and I want everything. I'm ok with a noisier fan at high speeds though - if whatever is cooking is sizzling and making smoke, I'm not too concerned about fan noise. Quiet at low speeds would be nice. But I mostly want something that works in terms of getting exhaust out and that doesn't break over time.

I have worked with KD's on layout, it's a tough spot and the one place I could move the range to would be right in front of a window. The setup I'm going with puts it on a peninsula that faces an eating area, and I'll do a deeper counter there so things can go right from the stove to a counter-top "buffet" setup. We did consider relocating but liked the placement and figured we'd spend a little extra on an island hood.

And, I'm definitely open to design input from you or @kaseki on the ventilation aspects of this. If I'm missing important details, let me know. Based on my research so far, I think 36' wide and somewhere below 900 CFM should be fine for my situation, does that seem like a mistake?

Thanks!

I may have left out some words due to repetition. The number of square feet refers to the entry aperture of the hood. For example, a 36 x 24 hood aperture would be 6 square feet, and would require 6 x 90 = 360 CFM actual, likely needing a blower rated at 540 CFM.

Pressure loss not only entails the ducting, but the baffles and the MUA path. Leaky walls are not exactly a free path for air.

A leaky house may be sufficient for MUA in practice (given that the blower rating takes the pressure loss into account), but the OP may live where aggressive code enforcement will demand at least a damper in a duct to the outside.

The rationale for 90 ft/min is based on ensuring entrainment into baffle gaps that typically are around 50% of the baffle area and have to deal with upward plume velocities of as much as 1.2 m/s.

See also the table (Figure 4) on page 9 of the Greenheck Guide available here: https://www.tagengineering.ca/wp-content/uploads/2015/02/KVSApplDesign_catalog.pdf

The discussion leading to that table should prove useful for background information. In particular, the Greenheck method vs. the linear feet of hood edge (all the way around for an island hood) method is discussed. (Note commercial cooking rarely is true island type; even located in the middle of a kitchen the hood is connected to the cooktop via a back section. There may also be side skirts on the hood.)

Last, let me point out that capture can fail under cross draft conditions, which are almost always worse for island/peninsula configurations than wall configurations.

360 CFM actual in a six-inch duct is 1800 ft/min. This is allowable, but may be a tad noisy. Internet sources of pressure loss vs. flow for straight and elbow duct sections should be consulted for comparison with the blower's fan curve.

Wow, there's a lot to think about with all this stuff. Thanks for the input and for clarifying what you meant re: square footage.

The ZLine hood I'm looking at has a 760 CFM blower, and at 36x21 that seems ok, right? I might need to get into the MUA question a bit further, but am I wrong to think I can pick the hood first and then plan for that detail?

I feel like the majority of kitchen hoods on the market are designed for 6" ducts, and because my run was simple (only one 90 where the vent enters the duct) and fairly short (about 11') I didn't think about it a lot more than that. 8" would also be pretty hard to fit in the space I'm using.

Does anything here seem terribly off? Honestly, I've lived without any sort of exhaust in my current kitchen, so I'd expect it would be hard for this not to be an improvement.

Do you have any favorite picks or suggestions in terms of finding a decent hood that will do what I need for under $1000? You seem to really know your stuff, so I'd love to know your favorites.

760 CFM rated should be plenty (assumes the fan curve is reasonably normal in shape). You could probably run it most of the time well under max power. A six-inch duct would be kind of restrictive if the actual flow rate achieved was around 500 CFM. Maybe it would prove to be self limiting; that is, as the flow increases, the duct pressure loss increases until it balances the flow vs. pressure loss of the fan curve (along with other added pressure losses).

Given free MUA, baffle pressure loss usually exceeds the duct loss. With restrictive MUA, then the MUA pressure loss is not predictable. With restrictive duct pressure loss, then baffle pressure loss is merely additive, not dominating.

You may see from this that one can choose the hood on the basis of capture fundamentals, but the blower, ducting, and MUA have to be considered as elements of one system.

I only know what I had to research for my own kitchen reno. Lots of reported research is out there, but it mainly addresses commercial purposes. It needs to be extrapolated to residential purposes and construction limitations. An engineering background helps.

I don't recommend hoods I haven't owned, although I am willing to criticize hood features that deviate too far from those needed for performance. My hood is the largest Wolf Pro Island hood ventilating a 36-inch induction cooktop and a proximate Cooktek induction wok hob. It, and its adjunct components, are not in your price range. I haven't priced any other hoods, and mine is 10 years old.

Thanks, @kaseki! That's good context.

I'm wondering if you have input on the exhaust duct - most of the fans I'm looking at seem to include some sort of backdraft damper near the fan, but I'm wondering about additional controls on backdraft, whether at the exterior vent cap (this will vent out the wall) or as inline, butterfly style backdraft dampers. I've wondered about whether it would make sense to add an inline damper near the end of the duct if the vent cap doesn't seem like it will seal well. Any suggestions? Thanks again for your time.

Unless a hood is ducted through the wall it is mounted on, and hence the duct is very short, I favor two dampers: One at the hood (more or less) and one at the vent cap (more or less). This helps keep the duct warmer, reduces drafts due to wind effects, and may also reduce flapping noise of the interior damper. Note that some exterior vent caps that incorporate an external blower have a damper on the exterior side of the motor. This also keeps out bugs.

Thanks!