4 feet is way beyond the recommended hood placement of 18-24" above the cooking surface. You'll have a grease-spattered window with a dysfunctional hood above it. IMO, sinks go in front of a window, not cooktops.

Thanks. But this particular class of hood is designed for higher heights (in fact the Zephyr suggests NOT placing it any closer than 4 feet to the cooktop). What I'm wondering is if it would work acceptably well, or if it's basically useless like downdrafts are.

You'll still have a grease-spattered window. I would not build that feature into my kitchen.

Unless that hood is 72” wide by 60” deep, it has zero hope of capturing the V shaped cooking product effluents as they rise. You’ll still get heat, odors, grease, steam, and smoke all over the kitchen. More CFM does not make up for lack of capture area. A cooktop in front of a window needs a minimum 6” of clearance to that required tempered glass window, with zero trim protruding into that noncombustible space. You can never ever have any window treatments. Cleaning any grate at that height will become a neglected chore, instead of the weekly pop into the DW easy task, And you’ll constantly be cleaning that window, band cause you’ve got completely inadequate ventilation planned.

You need a better design. Hire a Kitchen Designer,

Thanks for the feedback. The hood is 63" by 27". It would be placed relatively low for a ceiling hood, and it would vent straight through the roof (a vertical exhaust of only a few feet long). If the hood is located 4 ft above the cooktop, it would be located 7 feet from the ground, which would be easy for me to reach using the step stool we keep in the pantry.

Also, using back-of-the-envelope trigonometry, a v-shaped effluent rise that spreads 10 degrees would require 8.5" beyond the edge of the cooktop. For a 36" cooktop, that means 55", well under the 63" of the wider model. It's true that it wouldn't capture the entire depth, but if we leave some space between the cooktop back and window, it might be acceptable. This is our induction cooktop:

https://www.bosch-home.com/us/productslist/NITP668UC

Note that the center burner is centered and the side burners are 14" long, which means that effluent for the center burner should almost be covered (12"+8.5"+8.5"=31"), and almost for the sides (33").

The reason we are considering this as opposed to a conventional hood is for the design of the room. We would like to have a wall-to-wall window as in this rendering:

(Rendering doesn't show but there would be a 1-ft soffit where the hood would go)

Alternatively we would have to break up the windows like so:

I prefer the look of the panoramic view, but don't want to put form over function. My question is really whether or not a ceiling hood as we are considering could suffice in our circumstances.

Thanks!

Combine cooktop and ovens into a range and place it to the wall to the left. Add a secondary small oven under counter. Place the sink where you have the cooktop. Not crazy about the bulky and intrusive pantry either. Or the fridge location.

The whole thing needs a rework from a skilled Kitchen Designer.

It really depends on your cooking styles, how often you cook, your and guests tolerance for the odors of meals past, and your thoughts on health and IAQ.

What you are describing will do a quite poor job of exhausting effluent. If your cooking is limited to boiling water for boil-in-bag meals then not much of a problem. Cooking a small meal once a month then perhaps not much of a problem. Otherwise you could have quite significant problems. It Depends!!! :-)

More: https://www.gardenweb.com/discussions/5161173/hood-faq

.

That's very helpful kaseki, and gives me a lot to think about. Hadn't thought about the design of the ceiling extractor vs a traditional wall one.

The reasons we are wanting the sink on the island, rather than the window, is to keep the cooktop off the island. I like having the sink across from the island for cooking efficiency, and I also would prefer that the sink face the center of the room rather than window since I spend more time during prep.

My sense is that it's probably too much of a compromise to not use a traditional wall hood, and that we should forgo the panorama window.

For those weighing in on the overall kitchen design, I did a post on the kitchen design seeking feedback here:

https://www.houzz.com/discussions/5928597/kitchen-layout-feedback

OK so I've read the FAQ @opaone posted, as well as @kaseki's responses. It sounds like getting this to work at 4 feet is going to be require a commercial hood that will be quite large in area, and consequently, in CFM requirements.

So let me try to see if I can understand the requirements for a wall-mounted hood. I'd appreciate if you could double-check my work and give any additional feedback.

Suppose I went for a wall-mounted hood, located 30" above the cooktop. We will be installing a Bosch Benchmark induction cooktop (https://www.bosch-home.com/us/productslist/cooking-baking/cooktops/induction-cooktops/NITP669UC). The width of the burners is really closer to 32 inches, and the max burner depth is approximately 14 inches. Our biggest pans (certainly any used for pan frying) will be placed on the center burner, which I hope will help with catching effluent.

Following the 10 degree rule, I'd need about 5 inches beyond, so at least 42 x 24 inches for the hood if mounted 30" above cooktop. Using the 90 inches per foot rule of thumb, this would mean approximately 560 CFM.

Given all that, I'm wondering if something like this could be appropriate:

https://zephyronline.com/product/monsoon-dcbl-range-hood-insert/

It's 42 x 22.5 inches. (I'm not wedded to Zephyr by any means, I just like this one because it has some of the lowest rated somes I had seen, and it uses baffles, which I now realize is important for extraction effectiveness).

I'm open to other suggestions, but I also see that the FAQ pretty much points you towards commercial hoods, which I'm a little skeptical of pursuing. If it's actually required, then I am willing to make room in my budget for it. But I also have a straight shot out of our one-story roof that will limit the scope for using an external motor, so I'm likely stuck finding the quietest built-in blower I can. I also am not wild about the idea of having the hood extend too far over the cooktop depth wise, since I worry about it getting in my way while cooking if it's located just 30 inches above the cooktop.

Thanks again in advance for your feedback. I want to get this right, as IAQ is very important to me.

90 CFM/sq. ft. of hood entry aperture.

Hood size should consider the pan size, not just the hob size, if large pan use is considered and such pans will be used for high temperature cooking. (High ==>Temperature greater or equal to the smoke point of whatever cooking oil is to be used.)

Care should be taken to find a best compromise on cooktop location on the counter and hood position. Sometimes a smaller than optimal front-to-back size hood can be used spaced out with a panel placed at the back to fill the gap.

What isn't obvious at the Zephyr hood site is a fan curve for the blower to determine how much flow will result depending on various pressure losses, including imperfect MUA. However, 560 CFM x 1.5 should be sufficient for an adequate blower rating. (This cannot be an exact science without pressure vs. flow data for every part, hence significant approximations are usually employed.)

Thanks again @kaseki. Hadn't considered the fan curve. A couple follow-on questions, if I may:

1. If we install an adequate make-up air dampener, would the 1.5x increase in CFM rule of thumb still be required?

2. After reading the Hood FAQ and lots of posts, I am still pretty discouraged. There doesn't seem to be a clear "best" option that I can identify. Clearly the sentiment on here is that the ceiling-mounted hoods are severely compromised at best. Yet when I read the hood FAQ @opaone pointed to, it states that none of the residential brand hoods are up to the task either (mainly due to inadequate depth if I'm reading it correctly). So it seems like a 42" hood with 22" deep is still not good enough, yet I can't find anything that is deeper. So if I am left choosing between two inadequate solutions, I'm wondering how much "less bad" a wall-mounted hood at 30" above is vs a large ceiling mount.

Surely there is a way to get acceptable ventilation in a residential environment that doesn't require custom-ordering from a commercial hood manufacturer. But if there is, I haven't been able to find it yet!

A couple of quick thoughts...

DO NOT get hung up on CFM's. This is a marketing thing. A well designed hood with appropriate capture and containment can use far lower CFM's than a poorly designed hood. Commercial hoods require far fewer CFM's than you'd think.

Do though consider the fan curve.

Hood depth (front to back) is important and possibly more important than width. This is where you are standing which creates turbulence and a more spread out plume. This is why commercial hoods are usually at least 36" deep and often deeper.

Yes, there is a gap between consumer hoods and commercial hoods. Consumer hoods rely on marketing and CFM #'s make good marketing fluff. That a properly designed consumer hood (proper clear open aperture, appropriate containment volume, etc.) could cost less, be quieter and perform better w/ 600 CFM's than any of the current crop of 1200 CFM consumer hoods doesn't make for good marketing schtick. Commercial hoods are sold on performance (how well they exhaust effluent, how quiet they are, how easy to clean). Think about that commercial hoods are all very simple fairly inexpensive boxes with a gob of containment area - why?

There is no clear best option in consumer hoods because the only consumer hood with anywhere near adequate containment volume is Vent-A-Hood but their hoods are quite loud, difficult to clean, and the location of the blowers reduces their effectiveness.

That said, many people are quite happy with their hoods. Perhaps they don't realize how bad their house smells because of stale cooking odors or the harm that poor indoor air quality is causing them or they keep windows open all of the time or their range and style of cooking doesn't require a very well performing hood. Or they don't realize that there are better options that work much better and are much quieter.

Thanks @opaone. OK I have one more idea before I throw in the towel. What about a 54" wide Wolf Pro Island Hood? Could that work even though the cooktop will be against the wall? It's 34" deep (can't quite tell the dimensions of the catchment area). Wolf recommends placing between 30-36", but I'd need to mount a bit higher (probably 42" above the cooktop) since it would overhang the countertop and I'm 6'1". In this case, we could make the countertop jut out a few inches to give more space between the cooktop and the wall and to center better on the hood.

Might that actually work? I would worry a bit about exceeding the recommended height, but based on the calculations discussed in this thread, I think it would have adequate coverage at that height. Cooktop area is roughly 36" W by 15" deep, so the 10 degree calculations require adding 15 inches. That becomes 49" by 30" deep required for the hood.

My Pro Island hood internal capture aperture, front-to-back, is 26 inches, but the flats to the outside will have some performance, and certainly whatever is against the wall will count, as will any sides that meet cabinets. With respect to shape, note that the island hoods' outside contours have a curved shape. The internal aperture at the ends is about 3-inches less at each end than the overall hood long dimension.

It may be aesthetically nicer looking to treat the hood as an island hood and space it from wall and cabinets enough to look OK, and as you mention, bring the cooktop out a bit from the wall. More cabinet volume under the counter can always be helpful. I have wire racks in mine for maximization of induction cooktop cooling air volume.

It is unfortunate that Wolf doesn't supply a deep wall hood. (But my catalogs are old, so YMMV.)

My picayune wall hood.

Deep wall hood (Handcrafted Metal Inc.)

As for the increased height: I think you would be OK at a wall if the cross drafts are minimal. Upping the flow rate might help cover the case of a serious plume emitter. Judging from Figure 6, page 30.4, 2003 ASHRAE HVAC Applications Handbook, below the hood aperture the flow contour lines extend somewhat outward, giving the hood a tad more effective aperture area. Put another way, a 42-inch mounted height hood is "weaker" but "larger" measured at 36 inches above the cooktop.

Keep in mind that the goal is entrainment of effluent into the hood, and this will be easier with induction due to the reported lower peak velocity of the cooking plume (no hot gas combustion products).

Thanks, this seems like a promising way forward. And maybe we can stick it closer to 36 after all.

Tyler,
Same situation.
Wrath did you end up doing?
His is it working out?
Why did no one mention a downdraft?

@Laura Tater: Search on 'downdraft' in this forum for a load of discussion on why downdrafts cannot be effective against hot cooking plumes. Capturing the odor of boiling cilantro on a back burner might be possible, if you wanted to do so.

Re-reading this entire thread, I thought it worthwhile to inject one other thought with respect to the original post. The edge perimeter ceiling vent (no use of the word hood should apply) may depend on the rising and expanding plumes losing momentum with height such that reflection from all that metal is weak. In such a case there would be some horizontal plume spillage that the edges can, in principle, capture.

First, I have no velocity data for ceiling heights so I cannot disprove this concept, but I have my doubts. And such effects won't apply at seven feet ceiling height. Second, I stand with the argument that any ventilation air velocity high enough for the edges to capture and contain the effluent volumes that might be present would necessarily be noisy, albeit somewhat more removed from the cook than baffles or internal fan blade tip turbulence would be with a more conventional design, and in particular the historical VaH "Magic Lung" design.

I also wish to correct an impression that the OP apparently absorbed from @opaone's and my writings. In my view, for most applications, a proper residential hood will perform the needed functions of capture and containment (and grease fire propagation protection). With low reservoir volume at the bottom, residential hoods will require a higher CFM than a commercial hood would need for the same plume capture and containment (assuming not all hobs/burners are operating a maximum plume generation).

Stated differently, the recommended flow velocity from 90 CFM per sq. foot needed at the aperture of a residential style hood can be reduced at the aperture of a larger commercial style hood due to reservoir volume averaging of plumes across the entire cooktop.

Commercial designs are optimized for efficiency within the scope of applicable regulations. Their large entry apertures make them awkward for many residential kitchen layouts, and their intended height of 7 ft from the floor, while convenient for tall cooks, imply a high ceiling for the large reservoir, baffle assemblies, and other inside parts (the blower will be on the roof, usually).

Kaseki,
Thx. Yes, I’ve read many of the houzz forums on downdrafts. Our options are limited due to Reno a 1910 solid brick craftsman. This is not to say that anything is possible, as anything is possible when money is no object. I was curious as Tyler is debating many of the same things I am what he actually ended up with and if he’s happy with it. Thx so much for your additions to this thread. I found this thread very helpful thus far.

Laura: You might describe your cooktop environment. Is it against an exterior wall? Against an interior wall? Is there a nominal 7 -- 10 ft ceiling? What is above the ceiling? Do you thread-jack often? [Just kidding, we are pretty relaxed here.]

Our renovation is still going on. But we have purchased a 48" wide imperial hood over a 36" wide cooktop and placed it 3 feet above the cooktop, within the recommended distance. We followed kaseki’s rule of thumb to select a vent of around 90CFM per square foot of surface area, with of the hood, which is 8 square feet in our case.

In the end we decided that the dispersion of effluent meant that we had to lower the hood. Function trumped form in the end. Should know in about 6 weeks if it was worth it.

Function! Thanks

Tyler: Please clarify the following. Did you choose a blower rated at 720 CFM, or a blower rated significantly higher such that it would flow 720 CFM installed in the hood system subject to the MUA system? What is the front to back distance of the actual hood aperture, not the overall hood front to back dimension?

I chose a variable speed blower, goes to 1000 cfm. We installed makeup air. Actual hood aperture is slightly less than

24x48. More like 20x48. I was rounding up. (I also hit enter too soon ;)

6.7 sq ft x 90 ft/min = 600 CFM. A 1000 CFM rated blower should be adequate for 90 ft/min. I am surprised you got much dispersion, although 20 inches depth might be a bit skinny.

Project is finally done. Here is the final result. Hood seems to work well.

Thank you for getting back to us with a conclusion.

Looks quite awesome. I'd not want the poor exhaust in my kitchen but we all have different priorities and hopefully this works for you.

The kitchen looks great ... but am I the only one that was expecting some amazing lake or ocean view out of the panoramic windows that seemed to drive this project? 🙂

Tyler, so how is it going with the cooktop/hood? We are planning a remodel and considering a similar situation. We are in Florida, so I’d like to avoid MUA if possible as it is painfully humid and hot AF here 360 days of the year and one of my main goals of this remodel is to keep the hot air out. We have an older 1959 home, 94” ceilings. Our kitchen designer wants to put a 36” wolf gas range-style cooktop in front of a 104” window with a 6” backsplash/ledge using a wolf or zephyr 48” ceiling mounted hood at 600 or 700 CFM. So if the cooktop lands at 36”, that puts the vent 4’8”away from the countertop on the ceiling. I’m looking for functionality of suckage (sorry, I never made it past geometry into trig, so “suckage” is as good as it gets for me—lol) and if I have to use a different island hood that hangs 36” above the cooktop, so be it.

I’m curious how it’s going for you, especially cleaning the window after cooking. Is it a daily chore or weekly? (I don’t see the window as a cleaning issue, when I cook, most of the splatter winds up on me or flies sideways, but rarely backward—but I’ve been wrong before, and I’ll be wrong again). I just don’t want to make the hood mistake. Any and all input is appreciated ;)

Cooktop and hood are working out great. I would say that food splatter gets on the window once or twice a month max and we cook daily. It hasn't been a problem at all. More commonly we do get some splatter on the counter behind the cooktop. So I'm glad our cooktop bumps out 6 inches or so. That space ensures the window stays clean most of the time.

We mounted out hood 37" above the cooktop (1 inch higher than spec so my head doesn't hit). I am glad that we mounted it that high but I am also glad we didn't put it higher toward the ceiling as we originally considered. The window isn't really obscured by the hood. Any higher and I don't think it would work well.

And we did install MUA. If you don't then you need to install a hood with lower max CFM. That may be a compromise worth making but if you do, then I would surely mount the hood lower so less CFM is required.

Here's a side view, shows the gap between cooktop and window

Remember, everyone, that the rated flow rate is measured for the blower hanging in free air, and the actual flow rate will be determined by the blower's fan curve versus all the pressure losses from cooktop to outside and back to the cooktop. The less MUA you allow, the less air flow the hood will have, the poorer the capture of the effluent plumes, and also potentially the poorer the removal of grease by the baffles.

Nice photo @Tyler, clarifying the configuration.

Tyler, thank you SO MUCH for the response! You have helped me greatly in my decisions I’ll have to make in the near future.

Kaseki, it has been an education, to say the least. My kitchen designer has 30+ years experience and I’m doing my due diligence to make an informed decision on choosing a contractor (both applicants have 20+ years experience) and ventilation placement. Thanks to this conversation and a dictionary, I should be ready for the upcoming makeup air/CFM conversations with the professionals so that I’m happy and not disappointed with the outcome of my cooking setup. So, again, I thank you all 😊

Here’s something someone told me the other day when we were appliance shopping—I try to learn something new every day—she said to turn the vent on 10 min prior to cooking so the vent sets the ventilation pathway. Very interesting! I’m really looking forward to our new kitchen!

I personally think that unless one's house is measured in tens of kilo-square-feet, establishing a path should not take more than a minute. And this assumes that establishing a path is actually needed, as pressure differentials cannot be significant for very long, and practically any path will have some turbulence towards the sides of the path. Perhaps with an active controlled MUA system having the pressure sensor remote from the kitchen one would want time to stabilize, but such as design would be against principles of good servo control.

However, if it is winter and you want to warm the exhaust duct where it might pass through a cold attic to minimize grease and water condensation, then longer operation before sending up much effluent is a good idea. Sometimes dampers can be frozen shut and need some air disturbance to shake loose.

We live in South Florida, we don’t have winter. Best we ever get is 40s. I’d kill for a a week of 30s, though, it would kill off some iguanas taking over the state.

Hi, all, thanks so much for a great discussion. We are chewing on a similar issue—30” induction range going in a new island. The sightlines of an island hood really bug me—even a slimline—and having been talked out of the Best Cattura downdraft, I am trying to find a good approach. We’ll have an 18” ceiling overhang above the island, and i am wondering if i can mount a 48” vent hood flush to it, so that we don’t get any visual interruption and it would be hidden from the dining room side. The hood would sit 40 inches above the cooktop. i’ve attached some schematics—1) our designer’s plans with an island hood; 2) some rough drawings of my idea from sketchup; and 3) a photo of the space as it sits now. thanks in advance for any guidance!!

You can use the guidance above in this thread and in others to determine hood entry area for a 40-inch hood height. From that you can determine desired CFM (and counterpart desired MUA CFM) and from the desired CFM the necessary rated CFM of the blower.

As long as you can envelope a hood of the requisite size in the dropped ceiling (if I understood your question), and have a suitable duct path, then hiding the hood is not an issue. Be sure to consider cross drafts when deciding whether to chance a barely adequate entry size vs. a perceived overkill entry size. It doesn't require much of a breeze, or even particularly fast moving persons, to deviate a cooking plume.

Note that some below-the-baffles reservoir volume is better than none. (See the image of my Wolf hood above for barely adequate reservoir volume that works with heavy cooking because I can exceed 90 CFM/sq. ft and have induction hobs.)

@Lawrence Kluttz, this depends a lot on the styles of cooking you do, how often, other ventilation in your home, etc.

To capture 85% of the effluent @ 40" you'd need a hood OPENING of approx 41" x 35" but with an island approx 48" x 44". My guess is that the 48" hood you're looking at is about 46" x 25"? If so then you'll get maybe 40% and the other 60% will spread throughout your house. And this is assuming that your hood has sufficient containment volume and exhaust capabilities.

If you mostly boil water then this isn't a problem or if you have a lot of windows open all the time so that you get good ventilation from breezes through constantly then not a problem but otherwise you'll likely have a lot of VOC's and Carcinogens building up in your home.

Similar to your hood being out of sight, so too the harmful effects on your health until you're sick from them.

More: https://bamasotan.us/range-exhaust-hood-faq/