unconventional extractor fan ducting
 

so me and the missus were having a conversation last night about how we
want to do the kitchen when we can afford it. she talked, i listened.

anyway, we have a bit of a problem in this kitchen at the moment -
condensation. the building is about 250 years old, converted about 100
years ago from a hay barn into a house. so, one of our main priorities
will be keep it ventilated a bit better than it is at the moment.
we'll probably end up having a hood over the hob and a humidistat
controlled extractor fan.

the problem comes with getting this to the outside world. because of
an awesome arrangement of window/drains/boiler there is absolutely no
way to get through to the outside world above about 1m from the floor.
so, can we duct a combined extraction from the hood and the extractor
fan down the wall at some point so that we can get it through the wall
beneath the window somewhere?

is there any good reason not to do this other than it sounding like a
daft idea?

unconventional extractor fan ducting
 

Redeye wrote:

so me and the missus were having a conversation last night about how we
want to do the kitchen when we can afford it. she talked, i listened.

anyway, we have a bit of a problem in this kitchen at the moment -
condensation. the building is about 250 years old, converted about 100
years ago from a hay barn into a house. so, one of our main priorities
will be keep it ventilated a bit better than it is at the moment.
we'll probably end up having a hood over the hob and a humidistat
controlled extractor fan.

the problem comes with getting this to the outside world. because of
an awesome arrangement of window/drains/boiler there is absolutely no
way to get through to the outside world above about 1m from the floor.
so, can we duct a combined extraction from the hood and the extractor
fan down the wall at some point so that we can get it through the wall
beneath the window somewhere?

is there any good reason not to do this other than it sounding like a
daft idea?

nowt wrong with doing that but dont combine them, if you do your air
will go into the cooker hood and come outnthe ext fan or vice versa,
partially.

NT

unconventional extractor fan ducting
 

Redeye wrote:
so me and the missus were having a conversation last night about how we
want to do the kitchen when we can afford it. she talked, i listened.

anyway, we have a bit of a problem in this kitchen at the moment -
condensation. the building is about 250 years old, converted about 100
years ago from a hay barn into a house. so, one of our main priorities
will be keep it ventilated a bit better than it is at the moment.
we'll probably end up having a hood over the hob and a humidistat
controlled extractor fan.

the problem comes with getting this to the outside world. because of
an awesome arrangement of window/drains/boiler there is absolutely no
way to get through to the outside world above about 1m from the floor.
so, can we duct a combined extraction from the hood and the extractor
fan down the wall at some point so that we can get it through the wall
beneath the window somewhere?

is there any good reason not to do this other than it sounding like a
daft idea?


Its OK in theory, but in practice airflow goes down rapidly with pipe
length..you may need a fairly meaty fan and fairly large bore pipework.

unconventional extractor fan ducting
 

unconventional extractor fan ducting
 

Thanks folks.

The ducting would end up as an inverted U, although more like an
inverted J to be honest as the outlet would be a lot lower than either
inlet. With a bit of planning it sounds like I'd probably be able to
make this work.

Thanks again for your help.

unconventional extractor fan ducting
 

Redeye wrote:
so me and the missus were having a conversation last night about how we
want to do the kitchen when we can afford it. she talked, i listened.

anyway, we have a bit of a problem in this kitchen at the moment -
condensation. the building is about 250 years old, converted about 100
years ago from a hay barn into a house. so, one of our main priorities
will be keep it ventilated a bit better than it is at the moment.
we'll probably end up having a hood over the hob and a humidistat
controlled extractor fan.

the problem comes with getting this to the outside world. because of
an awesome arrangement of window/drains/boiler there is absolutely no
way to get through to the outside world above about 1m from the floor.
so, can we duct a combined extraction from the hood and the extractor
fan down the wall at some point so that we can get it through the wall
beneath the window somewhere?

is there any good reason not to do this other than it sounding like a
daft idea?

One issue might be condensation in the duct building up and unable to
get out, you might need some sort of clever drain.

--
Chris Green

unconventional extractor fan ducting
 

On 5 Jul 2006 05:06:21 -0700 someone who may be "Redeye"
wrote this:-

one of our main priorities
will be keep it ventilated a bit better than it is at the moment.
we'll probably end up having a hood over the hob and a humidistat
controlled extractor fan.

Most of the water vapour in a kitchen comes from the hob. Extracting
from it should reduce condensation dramatically. You might not need
anything else, unless there are some particular circumstances.

If the hob is also near where you put down dishes from the oven then
the hood can also extract the steam when the lid is removed.

the problem comes with getting this to the outside world. because of
an awesome arrangement of window/drains/boiler there is absolutely no
way to get through to the outside world above about 1m from the floor.

To add to what others have said, where a duct exits a building
"horizontally" it should slope down gently. Not only does this allow
condensation to drain away, it also stops rain penetrating too far.

If the duct goes up from the hood only slightly and then downwards
there should be no great condensation problem at the motor and no
need for any more drainage.

so, can we duct a combined extraction from the hood and the extractor
fan down the wall at some point

Junctions are available, with an airflow operated damper that will
allow air to flow from either or both ducts into a common duct. They
are reasonably effective, but not perfect.

so that we can get it through the wall beneath the window somewhere?

Remember that you don't want the fumes coming back in through the
window when it is open. As a very minimum I would fit an outlet that
will divert the fumes away from the window, either downwards,
sideways or a combination of both as best suits the location.




--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

unconventional extractor fan ducting
 

David Hansen wrote:
On 5 Jul 2006 05:06:21 -0700 someone who may be "Redeye"
wrote this:-

one of our main priorities
will be keep it ventilated a bit better than it is at the moment.
we'll probably end up having a hood over the hob and a humidistat
controlled extractor fan.

Most of the water vapour in a kitchen comes from the hob. Extracting
from it should reduce condensation dramatically. You might not need
anything else, unless there are some particular circumstances.

If the hob is also near where you put down dishes from the oven then
the hood can also extract the steam when the lid is removed.

the problem comes with getting this to the outside world. because of
an awesome arrangement of window/drains/boiler there is absolutely no
way to get through to the outside world above about 1m from the floor.

To add to what others have said, where a duct exits a building
"horizontally" it should slope down gently. Not only does this allow
condensation to drain away, it also stops rain penetrating too far.

If the duct goes up from the hood only slightly and then downwards
there should be no great condensation problem at the motor and no
need for any more drainage.

so, can we duct a combined extraction from the hood and the extractor
fan down the wall at some point

Junctions are available, with an airflow operated damper that will
allow air to flow from either or both ducts into a common duct. They
are reasonably effective, but not perfect.

so that we can get it through the wall beneath the window somewhere?

Remember that you don't want the fumes coming back in through the
window when it is open. As a very minimum I would fit an outlet that
will divert the fumes away from the window, either downwards,
sideways or a combination of both as best suits the location.



Random points

DO understand how long runs of pipework reduce flow rates DRAMATICALLY
and use MUCH larger diameter than you might think necessary.

DO consider that if the weather is suitable for open windows you
probably won't use the fan..

DO consider that gas cookers are the primary source of steam in a
kitchen. WE have oil Aga and electric hobs, and never get steamed up.

DO consider that steam is not the only thing you want to get out of a
kitchen. Fried mackerel is another :-) Humidistats are NOT recommended.

unconventional extractor fan ducting
 

The message
from The Natural Philosopher contains these words:

DO understand how long runs of pipework reduce flow rates DRAMATICALLY
and use MUCH larger diameter than you might think necessary.

And smoother. Crinkly flexiduct is very draggy.

--
Skipweasel
Pay no attention to that man behind the curtain.

unconventional extractor fan ducting
 

On Thu, 6 Jul 2006 12:17:40 +0100, Guy King
wrote:

The message
from The Natural Philosopher contains these words:

DO understand how long runs of pipework reduce flow rates DRAMATICALLY
and use MUCH larger diameter than you might think necessary.

And smoother. Crinkly flexiduct is very draggy.

Avoid 90degree bends too.

Mark