Lots of manufacturers make them. Some pop up higher than others (good or bad depending on your priorities). I would not recommend a pop up if you will be using gas or if you do a lot of frying or grilling.

One thing to look carefully at is the amount of space different models take up under the cooktop. Some can vent down (or out the back) and have remote blowers and will therefore take up little space. Others have the fan mounted in the cabinet and will leave you with very little usable cabinet space there.

I considered this option for my island cooktop but decided to go for an island hood because I didn't like the look of the popups when they are in use.

If you plan to have seating at the island, a popup can serve as a barrier to protect guests from splatters.

Had one by Dacor. I found it ineffective, especially with gas burners as it tended to tug at the flame and cause the burner to start 'ticking.'

Actually, I'm not talking about a pop up fan. What I'd like to know about is a regular above the stove vent hood that can be pulled down closer to the cook top when needed and pushed up higher when not in use so it doesn't impede the view. The only one we can find is the expensive Miele but it seems like it shouldn't be too hard to do.

The Zephyr island hood telescopes for installation, but not dynamically during use. It can be installed from 28" above the cooktop to 36" (8' to 10' ceilings with an extension for higher ceilings), but is fixed once the installation is complete. For the Zephyr it appears that ceiling height has some impact on the actual final height of hood -- we are working with the regional distributor to understand if this is true. Our 8'2" ceiling limits the hood to the 28" level, but presumably with the way the telescoping works you would have more options for final height with a 9"+ ceiling.

I did not look at the Miele hood, but am interested that the pipeing is capable of being flexible enough to dynamically telescope & remain sealed. There are accordian type vent pipes, but holes broke in those when "opened" & "closed" too often.

Actually having seen many island hoods (some with wonderful decorative boxes built around them) my husband & I were concerned that the Zephyr would bother us in the middle of the room. Since I do cook with gas & had struggled with a "downdraft" for years, the island hood was important. It is 6" wider than the cooktop (3" on each side) & we are so pleased with how it feels, not too heavy or obstructing our view. We have the Zephyr Europa Series -- Napoli.

Of course, if being able to raise the hood dynamically is important to you it might be worth the expense of the Miele.

From a safety point of view, I would think a pair of concentric tubes of sufficient length would be safe for residential use. (The bottom tube has to be the inside tube, and the flow has to include the leakage. However, island hoods of sufficient size are very heavy, so the mechanism for pulling the hood up would be more of an eyesore than the hood itself.

One of my contractors and I installed my Wolf island hood. However, we had the help of a hydraulic sheet rock lift to hold it up while we aligned and attached the hood. A large enough hood that was light enough to easily lift would seem to either lack required volume and filter mechanisms, or be an oxymoron.

If the hood in question is the DA424V, my impression from an on-line image is that the shape is not conducive to effective capture and containment, the two functions of a hood. The flat base allows rising effluent to "bounce off" before the filters can capture the effluent. The thin volume above the filters would be expected to cause unequal flow across the screens, making the periphery less effective.

In evaluating hoods, one approach that may help is to look at commercial designs to see how they perform their functions, and then consider how far one can depart from this genre for aesthetics sake and still have an effective hood, rather than a multi-thousand dollar ceiling ornament.

kas

Thanks everyone. It gives us lots to think about. We certainly don't want to spend $ on something that will be ineffective. Maybe will just have to consider the fan as part of our view.

I am also looking at the Miele DA424V - My question to the rep was whether having a 625 CFM (Miele 48" DA424V) hood at 28" above the range is better than a Zephyr Trapeze 48" 1000 CFM hood at 36" above the range. I am trying to maximize my view when in the kitchen when I am not cooking a very smoky dinner. I plan on putting the hood over a 36" Bluestar range with griddle. I don't imagine using all 4 burners at the same time (which would require a minimum of 680 CFM). The rep said that it is a wash since you need to add 200-300 CFM for every 3" you move above 30" - so better to not waste money on the higher CFM hood. He also said the Miele would trap better because it is 27 1/2" versus 26 5/8". So I am thinking I will get the Miele and keep it at 28" when using the wok or pan frying anything and keep it at 40" when I am doing something less smoky. I figured that flanking a 36" range by 6" each side will also help with the low CFM. The only unknown is the noise level when I am maximizing the Miele at 625 CFM - he said he was checking on the sone levels and will get back to me. Any other thoughts for or against going with the Miele would be greatly appreciated.

jlong9
"The only unknown is the noise level when I am maximizing the Miele at 625 CFM".

Disregard the sone levels on these two hoods and compare apples to apples.

A larger blower produces less noise than a smaller blower when generating equal CFM's. The duct size will also be a major factor in the noise. The Miele requires a 6 inch diameter duct and 625 CFM's through this will be noisy. The Zephyr requires a larger duct and uses a 1000 CFM motor. Although this is possibly quite loud at full bore, at 625 CFM's or less, the noise is greatly reduced. IMHO regarding hoods, bigger is better. Hoods don't make noise, bad installations, bad designing, bad budgets, and bad recommendations do.

I think that there is a mistaken view expressed earlier in this thread. That is, that more cfm makes up for a higher hood. This is true only if the hood grows in aperture, as it should, to accommodate the expanding effluent. Hoods do not suck up air from the cooking surface. They collect air that rises up to meet them. The air velocity measured at the hood aperture rapidly falls with distance below the hood and to the sides. (See the 2003 ASHRAE Handbook "HVAC Applications," Section 30 for flow contours.)

Make the hood wide and deep enough to capture the rising effluent, then make the flow large enough that the velocity of the air at the intake (or at the baffles if the hood directs the collected effluent toward a reduced area) is at least equal to the velocity of the uprising cooking plume (about a meter per second).

kas

If money is no object there is a commercial technique I've seen pictured that would get the hood out of the way; I don't recall which site. It has the advantage of being totally inconspicuous.

The entire ceiling is perforated and the area above the ceiling acts as a plenum that captures the effluent and directs it to the exit ducting and roof fan. What a greasy nightmare, one might imagine. The missing detail is that a considerable amount of ultraviolet light is used to destroy the grease in the plenum and ducting.

Make-up air has to be introduced somewhere else in this case, such as along the base of a wall.

An intermediate solution to visual intrusion would be to embed a commercial sized hood into the ceiling area so that the portion that intruded was modest. The area of the hood would have to be large enough to capture the expanding effluent, as usual, plus some additional to compensate for the now more likely cross-draft turbulence disturbances.

kas

I have been following this thread with interest. A telescoping island hood would work really well for us; we are trying to not obscure the view from a nearby window. Thank you for all your comments.

Kaseki: Thank you so much for your easy to understand explanations. I am intrigued by your last solution of embedding a commercial hood in the ceiling. How big/powerful would such a hood have to be if one were using say about 45K btu and had a ceiling that was 9 ft high?

"ultraviolet light is used to destroy the grease in the plenum and ducting"

This would be great if possible. But there is no ultraviolet light in this universe that will destroy grease, or really do much at all to the grease. I believe that must have been added as a marketing inducement. The most you could hope for is that a UV/ionizer/filter combination could charge greasy particles in an exhaust mist and trap much of them. They'd still have to be removed from the system.

As I understood it at the time, the problem wasn't the mist, as that is generally expelled outdoors in most commercial as well as residential systems. The UV (which may have ionized the air, or may have generated ozone which would certainly react with grease) was intended for removing grease condensed in the plenum. I'll try to find time to dig up an example from somewhere, possibly Heydal.

First, for a contrarian view, I found a brief CaptiveAire tract attacking UV use for kitchen ventilation.
https://www.captiveaire.com/Sitedocs/CaptiveAire/Articles/IneffectiveTech.asp

But for claims of method of operation, see
http://www.foodequipmentnews.com/2009/02/how-does-uv-light-technology-in-an-exhaust-hood-system-work.html

And here is an interesting adobe document from a "UV" hood manufacturer.
https://www.halton.com/dh/CACgmFfqqGWrDQSKf0w8zBHUX2-dwdZ4lAr9zTfvOSjtWRR8n9nxkjjNufjM8LPS_Cc6Wjn8QrSvlp2iuJymiOJDPIU0vltdToAh/Halton_KVE-UV.pdf

Notice from this example how much better characterized commercial hoods are than residential hoods. Also, in this case the UV was used for the effluent rather than cleaning an air plenum.

Bottom line, the claim is that intense UVC photolyzes the grease.