Externally vented downdraft - any good?

[Flymeaway4]

We’re planning a kitchen extension and will have an induction hob in the island. Ceiling mounted extractor isn’t an option as ceiling is pretty low already. We’re taking up the floor anyway, so can vent it outside, as opposed to recirculating.

Can anyone share their real life experience of a downdraft? Is it as good as a conventional extractor, or should we redesign in order to fit a conventional one? Is it better to get an integrated hob and extractor, or separate? Any brands to go for or avoid? Thanks

In terms of specifics of the duct itself and fitting it, we used a regular plastic rectangular duct (kind you can get from screwfix etc) of 90x220mm. This was fitted into the insulation later of the subfloor (we just cut an hole in it) and below the screed layer.

We've now finalised the kitchen layout and picked the hob and the floor duct doesn’t exactly line up with the duct on the hob. However you can get flexi-ducting to connect the 2. In case the hob you pick has a round duct, you can also get round to rectangle connectors to link the 2 shapes. Hope that makes sense!

A consideration for when you do the kitchen design; you want as few turns in the duct as possible and as short a duct as possible, as increased length and turns reduced the strength of the extractor.

Any questions just let me know.

Sorry, forgot to say, we cut the channel in the insulation to house the rectangular duct, then fitted a polythene type membrane over the top to act as a barrier between the insulation and the screed. Then fitted UFH pipes, fixing them to the insulation layer, through the membrane. Then poured liquid screed on top. So it is compatible with UFH too and the pipes can go over the top of it.

Hello, all very useful info. I wonder if you can tell me how you arranged the cabinet unit below the hob. Did you manage to keeps any drawers or do you have a ‘empty’ unit, as is usually the case under a sink? Thanks in advance.

There’s an empty unit below the hob, so the top unit is a dummy drawer and then there are 2 real drawers below

Thank you both. How does the venting pipe route vertically towards the ground? Does it fit behind the lower pan drawers? (when they are closed they do not reach it?).

We got our kitchen from handmade kitchens of Christchurch and so ours was a bit more bespoke. I think it is designed to do that though. We got an Elica hob and they have some good diagrams online with dimensions etc, if that helps? They may be specific to that brand though

Thanks for the advice 👍