Outside ducting for kitchen island downdraft extractor

3 years ago

I am hoping to have a downdraft extractor or venting hob in my kitchen island, but I can’t figure out how they can be ducted outside.

A kitchen island is obviously in the middle of the room which means ducting must run under the floor to get to an external wall. If it runs under the floor then it can only exit the wall at ground level which leaves it susceptible to rain water and other blockages or even attack by animals.

Any rise in the ducting would result in condensation and grease problems as that will collect at the bottom of the rise so I’m stuck on how this is supposed to work.

I’m sure lots of people have solved this problem and I’m probably missing something simple so if anyone has an externally ducted island extractor and can describe their setup that would be great.

Featured Answer

Phil Scott
Original Author

3 years ago

Hi Kay,

The hob will sit underneath a beam in the ceiling so I couldn’t put a ceiling extractor directly above it. I could move the hob from under the beam, but then it wouldn’t be centred so I’m trying to avoid that if at all possible.

I know it must be possible as venting hobs/downdraft extractors are very popular so I’m just trying to understand how the ducting works as I’m sure not everyone runs them in recirculating mode.

Phil

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Comments (23)

PRO
Kay Moden
3 years ago
Hi Phil,

Is there a reason why you can't use a ceiling mounted one? They are significantly more efficient and it will solve your duct problem if site conditions allow.
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PRO
Kay Moden
3 years ago
Right, on the point of rising this to a higher level, we would normally call the manufacturer and ask them on the specification and if its ok to take the ducting in a certain way or another, maybe you can try this too.
A good extractor doesnt let grease out or create condensation. Everything would remain in the machine's filters. Im not sure if this applies to downdrafts thought. Hope this helps.
PRO
Luke BORA ASM London
3 years ago
Hi Phil, with Bora.com cooktop extractors it’s not a problem to ‘swanneck’ up and out of the wall above the DPC just as long as your ducting route isn’t to long and doesn’t already have to many turns in it. Kay is correct that grease and condensation are no issue.... however I would disagree with them/her about the efficiency. With a Bora the cooking vapours/grease are dragged down at the point they are made and I would say that is more efficient!! If you have anymore questions please drop me an email. L.salter@bora.com
Simon Tsang
2 years ago
Hi Luke. what is the maximum length can the ducting be. Looking at a BOra and the job would be nearly 3m away from the outside wall.
PRO
Luke BORA ASM London
2 years ago
Hi Simon, 3m is fine. Our rule of thumb is up to 6m with up to 6 bends.
Simon Tsang
2 years ago
Sorry to hijack the thread. Which Bora model is equivalent to the Siemens IQ700?

https://www.siemens-home.bsh-group.com/uk/productlist/cooking-and-baking/hobs/venting-hobs/EX807LX67E
PRO
Luke BORA ASM London
2 years ago
either the "BORA Pure" or its big brother the BORA "X Pure" .
Oliver Little
2 years ago
Hi Luke, sorry again to hijack the convo - does fewer bends mean a longer distance? I am running a straight line from my island under the floor (i.e. straight down from the hob, wuth a single right angle to run under the floor)? Thanks
PRO
Luke BORA ASM London
2 years ago
Hi Oliver, yes possibly but i would check with a bora dealer or send me your kitchen plan & i can advise.
Fadeke Grace Afolabi
2 years ago
Sorry to barge in on the thread. @Oliver Little, I have the Siemens iQ500 Induction hob with integrated ventilation system 80 cm ED851FQ15E. Its on the island and the problems are 2 fold:

1. We can't get the connecting ducts adapter required. Does anyone know where we can find this?

2. Can we run the duct under the island down then across the kitchen floor for 3m to the wall?

Thanks
jolang1
2 years ago
Hi Phil

Did you ever get to the bottom of this as we are just about to embark on our build and want the same as you did? My husband doesn't get how the moisture gets fully extracted with the downward draft models. He thinks it will condense and not be able to get back up to ground level to be extracted put.

Many thanks

Jo
richard collins
last year
Hi there, I was reading this post 2 years ago when I was faced with the same question... what to do about a ground level extract for a venting hob. Our original kitchen had an overhead extractor. It has taken this long to get everything back on track post covid etc. Anyway, I got the builder to channel out a recess in the kitchen floor, then I installed 220 x 90 rectangular ducting. The builder made a 150mm circular hole using a core bit, drilled from the outside, right at the ground level, and at a slight upwards angle. Then I installed 150mm circular ducting into the hole and inserted a 150mm Naber Thermobox which has 3 flaps to contain the airflow, and it also means that any surface water, insects etc cannot get into the pipe. Inside the kitchen the ducting was covered with an 8mm steel plate so that it would be completely solid when walking on it, followed by a screed over the top and vinyl tiles. I've attached some images for you, I hope this helps anyone else who is considering a ground level extract for a venting hob. Try to ensure you have a good backflap mechanism and that the hole is drilled at a slight upward angle.
Oliver Little
last year
We ended up with the Bora (and non-bora branded ducting, which has been fine, despite the warnings from the Bora team to not go off brand…). ducting goes straight down from the island and then runs under the kicthen floor and patio to an airbrick built into the patio step. Distance from island to airbrick is c.5.5m. No issues (after 12 months) with condensation or anything similar. its the dream.
Simon Tsang
last year
following on from my post further up. we have now had our Bora with Bora ducting installed for nearly a year now all working perfectly well fantastic kit and no issues Touch wood
richard collins
last year
One other thing I would mention is to ensure you have adequate ventilation coming into the room when ducting out. Bora have a good article on this, with pros and cons of recirc vs ducting out. Keep an eye on this especially if you are using fireplaces, stoves, boilers etc at the same time as cooking. FWIW I'm glad I went with ducting out, but it does cost a lot more upfront.
Simon Tsang
last year
I agree if you are able to, go the ducting route. Not that re-circulating doesnt work. Friends of ours have re-circulating exteactor hood over an island, from a different manufacturer, they overlky happy with the performance compared to a ducted extractor
PRO
Earl & Calam Design and Build Ltd
last year
Hi, I cant find the photos, but the last one we did we used a ridged rectangular duct at below floor lever and came out in the render skirt just above ground level. Put a rectangular vent cover and works brilliantly.
HU-911773240
8 months ago
Hi @Oliver Little what brand ducting did you use? Many thanks
Oliver Little
8 months ago
Im afraid I dont know - builder’s choice (so i assume from one of the standard building supply providers)
J M
last month
Hello, can I run ducting under the units and through the wall instead of under the floor?
J M
last month
Hello, can I run ducting under the units instead of under the floor?
HU-694900881
last month
Do you have to have hob on the island?. We building extension with 2m Long Island in an L shaped kitchen, but I putting sink and hob against wall. Keeping island clear to work on and sit/ socialise at. Extractor can vent out through outside wall then.

Outside ducting for kitchen island downdraft extractor

Phil Scott
Original Author

Comments (23)

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Outside ducting for kitchen island downdraft extractor

Phil ScottOriginal Author

Comments (23)

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Phil Scott
Original Author