what type of ducting for kitchen extract

[Ouch77]

Got a cooker extractor hood on an internal wall which I'm trying to vent via the ceiling/floor void to an outside wall approx 3m away. The extractor hood arrived yesterday with about 1.5m of 125mm semi-rigid aluminium ducting. This obviously ain't goin to be long enough, so I'm looking to get a longer length.

Can I? nope.

Everyone wants to sell me short lengths of the corrugated aluminium stuff, I don't really want to make a joint as it'll be a pain if it leaks. There's other, more flexible stuff (looks like what you get with your tumble drier), but I'm unsure of it's suitability for a longish run, given it's higher resistance to the airflow.

Can someone recommend the right type of ducting suitable for a 3+m run with a single 90degree bend? There's a bit of cable and a CH pipe support noggin to avoid, so rigid duct would be tricky to install, but if it's definitely the right thing, then I'll do it.

 

[holmslaw]

How about this - http://www.fastlec.co.uk/aluminium-...-p-1761.html?zenid=77muv18ckgvolj6mg4n35fmgj1

 

[Ouch77]

How about this - http://www.fastlec.co.uk/aluminium-...html?zenid=77muv18ckgvolj6mg4n35fmgj1[/QUOTE]

Nice try, but unfortunately I need more than 3m to allow for the bend down to the extactor hood itself.

 

[Deluks]

Use an adaptor and convert to flat channel?
Joining flexi is easier with a short length of rigid pipe between the two. Use aluminium tape to seal, and go over the top with pvc 'builders tape' as the ali stuff can come unstuck.

Don't forget to insulate around the pipe if it passes through a cold area.

 

[Ouch77]

Use an adaptor and convert to flat channel?
Joining flexi is easier with a short length of rigid pipe between the two. Use aluminium tape to seal, and go over the top with pvc 'builders tape' as the ali stuff can come unstuck.

Don't forget to insulate around the pipe if it passes through a cold area.

I did consider changing to flat channel however I figured for the hassle of getting 2 types of duct, adaptors and different fixings it wasn't worth it. I also suspect that rectangular section won't flow as well, and as it's rigid I'd still have issues with obstacles.

Nice idea with the joints, I might do just that.

No need to insulate as the route is simply across the kitchen.

 

[mointainwalker]

If it fits, rigid PVC piping would be the best.

1) Reaonably cheap and available everywhere
2) Joints can be glued if you feel it is necessary but won't leak air anyway.
3) Minimal resistance to air-flow, therefore quiet
4) Very tough so you won't damage them when fitting
5) Lots of different bends available to negotiate noggins