Telescopic Downdraft versus Ceiling Mount Vents - BEST

8 years ago

I've bought a JennAir Induction 36" cooktop which is going to be installed in front of a window so no room for a 'proper' hood. I have never used a vent but from reading the forums it is best to have one. I really do not want to lose the cabinet space to vent a downdraft but other than putting it on the ceiling that it the only option. I do have room to either directly vent outside, if that is possible to get a blower outside in the elements (we live in the snow belt in Canada), in the basement or in the attic space. I have looked at the BEST Cattura Telescopic Downdraft which seems kind of awesome? But I did notice that their CIRRUS model can vent 72" above the cooking surface up on the ceiling. Does anyone have either of these? Do they work fabulously? Do you get grease on the ceiling with the CIRRUS? Or just not worry about it ... I have already gone 40 years without :) Pictures would be nice if someone has one installed?? Finding a price on these on-line is providing difficult too! Thanks so much!

Featured Answer

kaseki

8 years ago

The best cooktop ventilation depends on your priorities and constraints (more or less like everything else). In commercial practice, it is common to use large capture areas with apertures at about seven feet, but there are many possible approaches, including perforated ceilings leading to exhaust blowers. Commercial practice is heavily biased toward effective and efficient (power wise) capture and containment.

Residential practice can make use of commercial approaches, constrained by architecture, aesthetics, cost, and noise. Sometimes, however, the constraints force significant deviation from the most effective approach to capture and containment, considered to be a hood over the cooktop that has an aperture large enough to encompass the rising and expanding cooking plumes from the burners, and with enough air flow to ensure that what is captured is expelled outside.

Side draft ventilation will usually have limited ability to capture rising effluent from burners distant from the aperture without having a flow rate that is impractical and/or noisy. (The plume can have an upward velocity of 3 ft/s; the side draft is unlikely to "bend" that plume completely toward itself unless very tall and/or very strong.) A side draft can at least reduce the grease load on the house surfaces and cooking odors distributed beyond the cooktop.

Ceiling capture areas have to be large enough to not only encompass most of the expanding cooking plumes, but also the ever easier effects of cross drafts in deviating the plume direction. One would want a capture area of the cooktop size expanded by, say, 0.3 times the distance between the cooktop and the ceiling just for plume expansion without considering unknown to this writer cross draft conditions. So a 3 by 2 foot cooktop could at 5 feet above the cooktop require an added 1.5 feet of width and length. This now 4.5 by 3.5 ft aperture will need perhaps a bit lower velocity of blower air flow than the desirable 90 ft/min velocity at the normal hood height due to the plume cooling off some by the time it gets that high. Lets assume an average of 70 ft/min over the collection area is needed (this is a guess; I have no data for that distance above the cooking surface). This velocity times the area required computes to 1100 CFM. This will require at least a 1500 CFM zero-static-pressure rated blower in most circumstances, and a deliberate MUA system.

While roof hugging centrifugal blowers such as Abbaka, Broan, and Wolf sell can somehow operate in snow (I have a Wolf and it stays clear in southern NH), a more commercial style up-blast configuration blower would be better for deep snow conditions.

Some upblast blowers at Greenheck

kas

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Comments (8)

cpartist
8 years ago
Are you doing a reno on a kitchen or just replacing a cooktop? If it's a new kitchen you're doing I highly recommend posting your plans on the kitchen forum to see what the folks there could do to help you NOT have your cooktop in front of your window. It's probably one of the worst places to have a cooktop and in some jurisdictions in the US, it's not considered up to code.
rebecca3663 thanked cpartist
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I agree with rpg51. Down drafts can and do work when they are vented correctly. I worked for Jenn-Air (pre-Maytag / Whirlpool) and saw many in-home installations. Most done properly and some not so good. ie. back to back elbows, wrong size duct work and flexible duct work. Are they perfect? No. If you know what the limitations of a center down-draft are ahead of time you'll not be disappointed. Rear telescopic down-draft work very well too. Again, with all venting it needs to be done properly. Best Cattura 18" Down-Draft With regards to the Best Range Hood Cirrus built-in hood. Yes they do work. See the video link below. Here is my question to you. Who in your house is climbing-up the ladder to take down the filters and clean the stainless. Maybe not be bad at 9-ft leve but may be more of a PIA in at 12-ft. height. Best - Cirrus Range Hood Please note that the comments made by Futuro Futuro Kitchen Range Hoods is a company that does not offer a down-draft or true flush mount ceiling hood. If seems that if they can't complete in the category it is much easier for them to poo poo the options you are considering because they don't have anything to offer. To be fair to Futuro their hoods look like a direct hood import from Italy and seem to of reasonable quality. But, unless you're in Brooklyn, NY or Hallandale, FL it is difficult to truly judge the quality and the long term support for service. Ask those folks that who own a Elitair or TecnoWind hood and that are now orphaned. My recomendation is to look towards a nationally distributed brand and your local dealer for suggestions and long term support. Please let us know what you finally decide. Good luck.
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We have an old electric cooktop in our island (24 inch) that we are hoping to replace with an induction oven. We are looking into purchasing a telescopic downdraft versus a ceiling-mounted extractor hood from ikea (see below). Our limitation is that we do not want to install a new vent system. Would really appreciate any insight or advice in this regard. Thanks so much!
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Afarzin - when you are talking about a "24" cabinet", do you mean front-to-back or side-to-side? When you say "oven", do you mean "range"? (a range is a cooktop and oven combined in one appliance). Re the Oberoende hood you linked - I am not a fan of hoods with glass, because they show every splatter. Even though you think a glass hood will look "lighter", if you have to be cleaning it all the time, or looking at last night's splatter on it, the lighter look won't matter. I'll also link this one at Costco which can either exhaust to the outside, or recirculate - it does not have glass, and a pyramid shape is more effective than a flat shape: Island Hood at Costco Re the question of whether a downdraft exhaust that exhausts to the outside is better/worse than a ceiling hood that just recirculates: it kills me to say it, but I guess the downdraft is better of those 2 Evils. It's always better to have the smoke and grease exit to the outside. I just do not like downdraft exhausts compared to overhead exhausts, because as I said, they go against the laws of physics - smoke and grease travel upward, not sideways and down. Have you explored the idea of exhausting an overhead hood to the outside? Depending on your setup, it may not be that difficult or too expensive. It just depends on what your house is like. If you decide on a downdraft, look for the telescoping model that pops up the highest. Look for 12" to 14" telescoping height. Prices range from $1000-2000. I've seen Thermador downdrafts recommended on this forum. Thermador Downdraft
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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 ;)
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Melanie Rubery
6 years ago
kaseki, would you recommend a commercial exhaust like the Broan L700? I am wanting to put a 36 inch induction on our peninsula. Ceilings are 8 feet with no upstairs-one-level ranch home. Thank You!
Melanie Rubery
6 years ago
Also, what is the optimal CFM? Thank You!
kaseki
6 years ago
The L700 may be a commercial ventilator, but not a commercial kitchen hood. Its dimensions are completely in the wrong direction of size per my message above.

If you were to have a quasi-commercial kitchen hood mounted with its aperture at 7 feet (to the floor) or 4 feet above the cooktop, I would recommend that it be at least 52 inches wide by 34 inches deep. With induction, the hot cooking plume velocity isn't augmented by hot gas combustion products, so you might get away with 60 ft/min air flow at the aperture, equivalent to 60 CFM per square foot of aperture.

For this particular size, then, the area of 12 square feet calls for a desirable actual maximum flow rate of 720 CFM. Rated blower flow rate should be in the 1000 - 1200 CFM range (assuming appropriate make-up air). Hood should be aligned so that its center is midway between the cooking zones, exclusive of the cooktop controls.

If there is an attic, you might consider angling your duct so that you can fit a silencer and use a roof mounted blower. You probably wouldn't have room for a blower in a hood that is only 1 ft. to the ceiling unless some serious joist work in the ceiling is performed.

There are many hood manufacturers who can do special designs, including CaptiveAire and ModernAire.

If you are willing to keep the hood at a more standard maximum height above the cooktop of 36 inches, then any of the larger Pro Island hoods made by Wolf (and by others having similar dimensions) will suffice.
Melanie Rubery
6 years ago
Thank You! I will pass this information on to my builder. Do you have any input on the ceiling systems such as Zephyr Lux? Width is around 43 inches and depth is 27 1/2 inches. In this houzz image, they put it in a soffit to get it closer to the range. Thoughts? [https://www.houzz.com/photos/family-kitchen-contemporary-kitchen-london-phvw-vp~12046585[(https://www.houzz.com/photos/family-kitchen-contemporary-kitchen-london-phvw-vp~12046585)

Thank You
kaseki
6 years ago
I don't keep track of the near infinity of various hood systems. I only do requirements.

The minimum overlap of the hood aperture relative to the burners for reasonable capture is the tangent of 10 degrees times the height above the cooktop -- on each of four sides. And this requirement doesn't account for cross drafts, if any. Besides being a posed kitchen (at least it actually has a "hood" unlike some), this image's "hood" seems to be too small.

The most efficient hoods for capture and containment are commercial hoods. They have to be because power is not free, and whatever air is expelled has to be replaced, and possibly air conditioned. Moving to the residential realm, the question is always where the compromise is between aesthetics and performance, along with cost. You can deviate wildly from commercial design, but the performance is likely to suffer. If you insist on ceiling apertures, be sure that the size and flow rate is appropriate for capture and containment, respectively.

(And keep in mind that the baffles have to be cleaned, and standing on the glass cooktop of an induction unit is ill advised. Standing on any stone counter is ill advised. So some access to the filters scheme using ladders and planking should be planned.)
Melanie Rubery
6 years ago
Thank you-great information. I really appreciate it!

Telescopic Downdraft versus Ceiling Mount Vents - BEST

kaseki

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