I need to put in an extractor hood and would prefer an externally vented rather than recirculating system. However, the only route for the outlet duct is into the ceiling, horizontally for 2m, vertically for 3m through the first floor and into the loft and then horizontally another 2-3m exiting at the eaves. Most extractors seem to specify a max run of three metres. Do I have any options? Is it acceptable to add an in-line fan part way along the ducting to act as a booster? I should add i need an 'island' hood which seems to limit options somewhat.

Cheers,
Matt.

Hi Matt,

You have U2U

Bob

I wouldn't have thought a longer run would be much of a problem, I mean the air's not going to leak out. I suppose any grease would settle and cause problems down the line... and a fan halfway down (I can see) getting greased up.. Maybe one nearer the exit?

Perhaps a stupid question and something you've already ruled out, but can you run the duct horizontally through the ceiling then exit through the nearest exterior wall? Provided your kitchen has an external wall of course.

Rich

Unfortunately the joists run the wrong way to run to the external wall

U2U Jon Ison,

If I remeber correctly he has an ebay company selling cooker hoods . He is reansnobally helpfull - unless he is trying to kill himself arround cadwell with a screwdriver gearstick .

ATB agriv8

The long vertical run will have a flue effect ---- warm air rises

If worried stick a shower fan on the outside wall, use one that works on moisture content so it kicks off when required ?

Not that expensive from B&Q, as its not hazardous like a fire flue I do not suppose you need anything really apart from external flaps so it cannot be blown into.

Regards Mark

Could you make a feature of a surface mounted duct on the kitchen ceiling? Brushed stainless or painted in sympathy with the rest of the decor.

I'd be concerned about condensation and grease build up in a long run and with vertical sections it would pool in the first horizontal run.

That is a long run, but there are many things you can do to mitigate it. Use 6" solid pipe (ie smooth internal bore), proper corners etc. Grease build up isnt an issue, it will only minutely affect the bore size.

Only drawback with a long or restricted run is that the fan can be noisy on full speed, due to backpressure, and sometimes incorrect ducting can invalidate your warantee due to motor strain. However, extractors arent that complex and in my experience dont tend to break.

Another solution is to remove the motor from the extractor, and fit a remote, more powerful one, further away. Benefit here is also quieter running.

Have you considered a downdraft extractor, that rises out of your worktop and ducts below the floor?

PS i wouldnt just add a second fan myself without matching the extraction volumes. Most bathroom type fans would just restrict the flow, and a big powerful one could make the kitchen end run too fast.

[Edited on 4/4/12 by JoelP]

You can reduce standard ducting down to about 3inches of flat tubing screw fix sell it, you cold drop your ceiling if your really insistent on a duct, personally for all the hassle I'd recommend a GOOD filtered unit plus an extract fan on a kitchen wall...

Dave

http://www.screwfix.com/p/100mm-mixed-flow-fan/26867

Thanks for the suggestions everyone, some food for thought!