Hi all,

I'm planning to install some plastic ducting to take the output from
our cooker hood to the outside. Unfortunately the cooker is mounted on
an internal wall - there's no other place it can sensibly be. It's
going to be about 3m to the outside.

I've been looking at the rectangular plastic ducting on Screwfix - I'm
pretty sure I could build a suitable system using this stuff, but I'm
worried that the plastic won't be up to the job. Has anyone tried it
for this kind of application? Also, what kind of external vent is
recommended - a simple airbrick, a downward pointing vent or one with
flaps?

Cheers

Charlie

"Charlie" wrote in message
...
Hi all,

I'm planning to install some plastic ducting to take the output from
our cooker hood to the outside. Unfortunately the cooker is mounted on
an internal wall - there's no other place it can sensibly be. It's
going to be about 3m to the outside.

I've been looking at the rectangular plastic ducting on Screwfix - I'm
pretty sure I could build a suitable system using this stuff, but I'm
worried that the plastic won't be up to the job. Has anyone tried it
for this kind of application? Also, what kind of external vent is
recommended - a simple airbrick, a downward pointing vent or one with
flaps?

Cheers

Charlie

Just done exactly the same thing, but haven't powered it up yet, so I hope
it works! However, I used 150mm rectangular ducting from TLC because a) the
hood instructions specified it and b) I would have anyway as you want to max
out the extraction in a kitchen. There was a matching airbrick which I
installed, although they do do the square vents and the one with the flaps.
No idea which is better. Maybe someone has an opinion. If you can get away
with one 90 degree turn at the top of the hood and then a straight run to
the outside, this gives the best possible airflow.

Alistair

One good idea someone suggested to me was to run the ducting between
the ceiling and the upstairs floor! Though it depends which way your
joists go whether that is practical or not!

If it was hidden it would really matter what ducting you used.

HJWD wrote:
One good idea someone suggested to me was to run the ducting between
the ceiling and the upstairs floor! Though it depends which way your
joists go whether that is practical or not!

If it was hidden it would really matter what ducting you used.

I ran mine in a lowered ceiling - built to also even out the ceiling
heights in a knocked-through dining-room/kitchen as well as to quickly
solve the problem of what to do with the existing artex, ceiling
downlights and fake beams!

This approach meant I could take full advantage of the 500m3/hr
(freeflow) fan output by using 6" ducting consisting of a 4m run with a
90deg bend. The end result, both aesthetically and performance-wise, is
superb.

A few photos if they're of any use/interest:

http://www.newtonnet.co.uk/house/20041213/
http://www.newtonnet.co.uk/house/20050305/

In order to ensure a sufficient angle drop (condensation run-out)
whilst minimising the ceiling drop for such large ducting I cut out a
section of the existing ceiling for it to at least start in. The
reasons I couldn't simply use the existing ceiling void for the whole
length were that a sufficient drop was difficult (although rectangluar
ducting would've helped) and joist ran perpendicular to the others at
the outside wall - I think the other joists sat in this, not to mention
a nearby upstairs chimney breast, so having to cut a whopping great
hole in it made me too nervous!

Mathew

Charlie wrote:
Hi all,

I'm planning to install some plastic ducting to take the output
from our cooker hood to the outside. Unfortunately the cooker is
mounted on an internal wall - there's no other place it can
sensibly be. It's going to be about 3m to the outside.

I've been looking at the rectangular plastic ducting on Screwfix

Yeah, we did this with the screwfix kit - it was fine. Circular adaptor for
the cooker hood, and then rect ducting on top of the wall units to the o/s
wall, terminated with a downward pointing vent. The shape is good to hide
away, and it goes through brickwork nicely (because you can rake/drill out
the mortar courses and work with whole bricks). Good airflow, worked for
2yrs now.

"Steve Walker" wrote:

Charlie wrote:
Hi all,

I'm planning to install some plastic ducting to take the output
from our cooker hood to the outside. Unfortunately the cooker is
mounted on an internal wall - there's no other place it can
sensibly be. It's going to be about 3m to the outside.

I've been looking at the rectangular plastic ducting on Screwfix

Yeah, we did this with the screwfix kit - it was fine. Circular adaptor for
the cooker hood, and then rect ducting on top of the wall units to the o/s
wall, terminated with a downward pointing vent. The shape is good to hide
away, and it goes through brickwork nicely (because you can rake/drill out
the mortar courses and work with whole bricks). Good airflow, worked for
2yrs now.

Always seemed like a bodge to me, significantly less flow than the
round stuff and almost guaranteed that the duct wouldn't line up with
a single brick.


--

On Tue, 25 Oct 2005 13:58:26 GMT, Charlie
wrote:

Hi all,

I'm planning to install some plastic ducting to take the output from
our cooker hood to the outside. Unfortunately the cooker is mounted on
an internal wall - there's no other place it can sensibly be. It's
going to be about 3m to the outside.

I've been looking at the rectangular plastic ducting on Screwfix - I'm
pretty sure I could build a suitable system using this stuff, but I'm
worried that the plastic won't be up to the job. Has anyone tried it
for this kind of application? Also, what kind of external vent is
recommended - a simple airbrick, a downward pointing vent or one with
flaps?

One slight problem I should have mentioned - I can't use the void
between the ceiling and floor above (don't ask, but it's something to
do with a really badly fitted bathroom floor)- which is why I like the
idea of the rectangular ducting as it should look ok mounted on the
ceiling.

Thanks for all the responses, I think I'll be ordering stuff from
Screwfix.

C

Cheers

Charlie

On Tue, 25 Oct 2005 22:57:18 +0100, Matt
wrote:

"Steve Walker" wrote:

Charlie wrote:
Hi all,

I'm planning to install some plastic ducting to take the output
from our cooker hood to the outside. Unfortunately the cooker is
mounted on an internal wall - there's no other place it can
sensibly be. It's going to be about 3m to the outside.

I've been looking at the rectangular plastic ducting on Screwfix

Yeah, we did this with the screwfix kit - it was fine. Circular adaptor for
the cooker hood, and then rect ducting on top of the wall units to the o/s
wall, terminated with a downward pointing vent. The shape is good to hide
away, and it goes through brickwork nicely (because you can rake/drill out
the mortar courses and work with whole bricks). Good airflow, worked for
2yrs now.

Always seemed like a bodge to me, significantly less flow than the
round stuff and almost guaranteed that the duct wouldn't line up with
a single brick.

Agreed. Always use round ducting if you can fit it in. Use as few
bends as possible (avoid 90 degree bends).

Mark.

Matt wrote:

Always seemed like a bodge to me, significantly less flow than the
round stuff and almost guaranteed that the duct wouldn't line up
with a single brick.

I'll admit we were lucky with position - the height was right, and the
lateral could be adjusted an inch or two because it was out of sight on top
of the cupboards. Can't really comment on peak airflow, but it amply
copes with a £50 Comet hood.

Steve Walker wrote:
Can't really comment on peak airflow, but it amply
copes with a £50 Comet hood.
^^^^^^^^^^^^^^

That'll be why it copes then...! ;-)

Mathew