A whole passel, which I'm sure others here will be happy to bring to light. I'll stick to venting about ventilation.

From a ventilation efficiency standpoint (acquisition cost and operational cost), cooking at a wall (preferably an exterior wall or where a duct stack can reach the roof) is best. Where these increased costs for a given ventilation performance are not deemed significant, island or peninsula cooking is feasible to ventilate.

However, adequate ventilation performance is not achieved by pop-up down-draft systems unless the hottest oil/grease laden cooking is simmering bacon. And even then the simmering has to be done proximate to the down-draft intake assembly. Due to the nature of flow into apertures the actual flow rate into a down-draft will be limited no matter what blower is used. Further, the transverse velocity of this airflow over the cooktop will rapidly decrease with distance and front burners/hobs will not see much plume collection beyond capture of nearly zero upward velocity steam.

Due to the potentially high velocity of cooking plumes resulting from such cooking as searing or stir frying, overhead capture and containment is needed. This means a hood above the cooktop that is ducted outside via whatever path is feasible. Size and flow rate of island hoods not only have to account for plume expansion with rise, but also cross drafts and turbulence from persons in the room.

I have a hood over a peninsula containing an induction cooktop and induction wok hob. The ceiling is at 8 ft, but without the chimney extension, a 7-foot ceiling could have been accommodated. My attic is above, so no chases through bedroom closets were needed.

If I were you, I would seriously evaluate the need for island cooking and/or the perceived necessity for a down-draft ventilation system.

Basics start with a review of the first dozen or so pages of this tract:

https://www.tagengineering.ca/wp-content/uploads/2015/02/KVSApplDesign_catalog.pdf

Can you post a drawing of your floorplan? Maybe people will be able to generate some alternate solutions.

Thanks, everyone. I've been reading about the inefficiences of downdraft for months. I get it and I believe it. This is a well researched and considered decision based on the specific needs of our open plan space, and the compromise in ventilations will be manageable per the kind of cooking we do, and worth the maximization of views (and limitations of the 7' ceiling). If anyone has an opinion specifically on the cooktop with stove next to it (under counter), that's where I'm hoping for some ideas. Again, I know that a wall stove and a cooktop on an island are common, and that what I am proposing is not common. But I'm wondering if there are concrete reasons not to do this side by side on island countertop and oven approach. Thanks again, all!

We did that bc we wanted a 36” induction cooktop and there were no 36”ranges on the market then. we love having pots under the cooktop and open counter over the oven to put trays on. We have a narrow drawer stack between them for utensils and such.

I’ve Installed a wall oven in an island. For my client it was an ‘extra’ oven since their renovation had a 48” gas range with oven but they had recently replaced their w/o prior to renovating so was a shame to waste it. No issues other than the usual making sure the cabinet box is the correct size etc.

"...I am looking at an induction cooktop with pop-up downdraft behind it. The question is: where does our oven go? We cannot install a wall oven..."

Depending on how the blower is installed and the hood vented, a cooktop with a wall oven below it can be installed with the Best Cattura D49M30SB downdraft hood. The "Bosch Cooktop/Built-in Oven Approved Combination Guide" (for example) shows which Bosch-brand cooktops and wall ovens can be installed together. GE Profile cooktops and wall ovens can also be installed this way.

Thanks for this, wdcruise! The GE Profile downdraft makes it very clear that it cannot be installed behind a cooktop/builtin combo. I will look into Best Cattura and Bosch!

No add on downdraft is compatible with an oven underneath the cooktop. The plenum still takes up vertical room, plus the ventilation needs for the cooktop itself normally force the oven into the toe kick area on a standard oven under a cooktop install, even without the added obstacle of the downdraft. If you want an oven, it has to go into an adjacent cabinet. Which, if the island is actually physically large enough to do a proper island cook zone, is not an issue. Other than needing more electrical run to the island. But, since downdrafts are so useless, this design idea should really be abandoned.

"GE Profile downdraft makes it very clear that it cannot be installed behind a cooktop/builtin combo."

I see that: because the blower box is at the front which increases the depth of the hood to 7-1/4". But that doesn't mean that you couldn't use a Profile or otherbrand cooktop and oven with a Cattura hood.

Here are a few of CR-recommended 36" induction cooktops and 30" wall ovens, respectively, from the same manufacturer that might be compatible:

• LG Studio CBIS3618B + LG WSEP4727F
• GE Profile PHP9030DJBB + Café CTS70DP2NS1
• Whirlpool WCI55US0JB* + KitchenAid KOSE500ESS

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*not a CR-recommended cooktop

Thank you everyoen for your input. I know opinions are strong about the "uselessness" of downdrafts, and I know that lots of people read these forums, and that reading that can be discouraging for people like myself who are caught between a rock and a hard place with options. So I want to add here that rather than abandon the topic it might be helpful for others to know that I recently visited a friend's house to see and hear about her personal experience with her cooktop and pop-up downdraft. She's had it a couple of years now and is very happy. She does not notice grease on the ceiling or the light fixture hanging from it, and she cooks a lot. She said if she fried greasy hamburgers often she might like it less but she does so infrequently and it isn't an issue. She also acknowledged that the back burners receive more benefit than the front. I don't think anyone would argue that downdraft is as efficient as other ventilation approaches. It is a compromise. But usually compromises have to be made somewhere, and those are individual decisions.

Thank you! I'll look into that option.

Put me in the same camp as your friend. I have had a wolf cooktop in an island with a downdraft since 2004, Only option I had, and stuff gets fried several times a week, especially bacon.

Is it as good as a hood...of course not. Does it smell like bacon for a few hours,,,yes. Is there a greasy residue on the two glass pendant lights hanging over the island...no, and never has been. Is the 8 foot ceiling greasy or stained...nope.

This is my experience, Sometimes you have to do what you have to do.

PS.. to answer your original question, the only downside I see is the storage space you will lose. I have storage under the cooktop, but it of course is limited