We're having our kitchen extended and the architect has noted (on our
building plans) that we need an air extraction rate of 60 l/min. Question:
Can this all be catered for just using a cooker hood (extraction to the
outside), or does it need a 'higher up' fan?

On Mon, 23 Jan 2006 16:57:24 -0000 someone who may be "Grumps"
wrote this:-

We're having our kitchen extended and the architect has noted (on our
building plans) that we need an air extraction rate of 60 l/min. Question:
Can this all be catered for just using a cooker hood (extraction to the
outside), or does it need a 'higher up' fan?

You may not think this a helpful reply, but that depends on the
cooker hood.


--
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

David Hansen wrote:
On Mon, 23 Jan 2006 16:57:24 -0000 someone who may be "Grumps"
wrote this:-

We're having our kitchen extended and the architect has noted (on our
building plans) that we need an air extraction rate of 60 l/min. Question:
Can this all be catered for just using a cooker hood (extraction to the
outside), or does it need a 'higher up' fan?

You may not think this a helpful reply, but that depends on the
cooker hood.

Agreed, although I think your average cooker hood is designed to provide
adequate ventilation to your average kitchen... it would be a bit of a
mess to have a cooker hood slurping up 90% of the steam and fumes from
the hob, only to have 10% sucked away across the room to the extractor
fan on the opposite wall!

David

Lobster wrote:
David Hansen wrote:
On Mon, 23 Jan 2006 16:57:24 -0000 someone who may be "Grumps"
wrote this:-

We're having our kitchen extended and the architect has noted (on
our building plans) that we need an air extraction rate of 60
l/min. Question: Can this all be catered for just using a cooker
hood (extraction to the outside), or does it need a 'higher up' fan?

You may not think this a helpful reply, but that depends on the
cooker hood.

Agreed, although I think your average cooker hood is designed to
provide adequate ventilation to your average kitchen... it would be a
bit of a mess to have a cooker hood slurping up 90% of the steam and
fumes from the hob, only to have 10% sucked away across the room to
the extractor fan on the opposite wall!

OK. Say the hood in question has an extraction rate 2 times what is
specified by my architect. Is that going to be adequate, or is one still
needed at ceiling height?

In message , Grumps
writes
Lobster wrote:
David Hansen wrote:
On Mon, 23 Jan 2006 16:57:24 -0000 someone who may be "Grumps"
wrote this:-

We're having our kitchen extended and the architect has noted (on
our building plans) that we need an air extraction rate of 60
l/min. Question: Can this all be catered for just using a cooker
hood (extraction to the outside), or does it need a 'higher up' fan?

You may not think this a helpful reply, but that depends on the
cooker hood.

Agreed, although I think your average cooker hood is designed to
provide adequate ventilation to your average kitchen... it would be a
bit of a mess to have a cooker hood slurping up 90% of the steam and
fumes from the hob, only to have 10% sucked away across the room to
the extractor fan on the opposite wall!

OK. Say the hood in question has an extraction rate 2 times what is
specified by my architect. Is that going to be adequate,

Yes.

or is one still
needed at ceiling height?


Why do you think you need one at ceiling height?

--
Chris French

chris French wrote:
or is one still
needed at ceiling height?


Why do you think you need one at ceiling height?

With an oven under a hob the one extractor ought to be fine.
But with an eye-level oven separate from the hob (IYSWIM) then any
vapours
or smoke coming out of the oven will not be so easily sucked out by the
cooker hood.

Whatever you choose, I'd recommend installing a "damper" as per the
BES web site www.bes.ltd.uk so that when a gale blows outside you don't
get
a draught down your neck.

HTH

Mungo

chris French wrote:
In message , Grumps
writes
Lobster wrote:
David Hansen wrote:
On Mon, 23 Jan 2006 16:57:24 -0000 someone who may be "Grumps"
wrote this:-

We're having our kitchen extended and the architect has noted (on
our building plans) that we need an air extraction rate of 60
l/min. Question: Can this all be catered for just using a cooker
hood (extraction to the outside), or does it need a 'higher up'
fan?

You may not think this a helpful reply, but that depends on the
cooker hood.

Agreed, although I think your average cooker hood is designed to
provide adequate ventilation to your average kitchen... it would be
a bit of a mess to have a cooker hood slurping up 90% of the steam
and fumes from the hob, only to have 10% sucked away across the
room to the extractor fan on the opposite wall!

OK. Say the hood in question has an extraction rate 2 times what is
specified by my architect. Is that going to be adequate,

Yes.

or is one still
needed at ceiling height?


Why do you think you need one at ceiling height?

Because my Draft 2006 copy of the building regs (section F1) says that
mechanical extractors and fans should be preferably less than 400mm from
ceiling height. Of course, the use of the word preferable must leave it open
to interpretation. And there is also the question as to whether additional
ventilation is required in the first place.

Mungo wrote:
Whatever you choose, I'd recommend installing a "damper" as per the
BES web site www.bes.ltd.uk so that when a gale blows outside you
don't get a draught down your neck.

The cheap-as-chips bottom of the range hood I fitted a few weeks ago had
one included within it, actually.

Dvaid

We're having our kitchen extended and the architect has noted (on our
building plans) that we need an air extraction rate of 60 l/min. Question:
Can this all be catered for just using a cooker hood (extraction to the
outside), or does it need a 'higher up' fan?

Be careful if you are using any length of ducting. Any significant length
will annihilate the extraction rate, especially if it is an axial fan,
rather than centrifugal. If it is straight through an external wall, then
there is no problem.

Christian.

Christian McArdle wrote:
We're having our kitchen extended and the architect has noted (on our
building plans) that we need an air extraction rate of 60 l/min.
Question: Can this all be catered for just using a cooker hood
(extraction to the outside), or does it need a 'higher up' fan?

Be careful if you are using any length of ducting. Any significant
length will annihilate the extraction rate, especially if it is an
axial fan, rather than centrifugal. If it is straight through an
external wall, then there is no problem.

Thanks.
It'll be a twin centrifugal fan unit, and straight through to the outside.

It'll be a twin centrifugal fan unit, and straight through to the outside.

I hope you can turn it down!

Did you buy the optional wind tunnel attachment?

Christian.

Christian McArdle wrote:
It'll be a twin centrifugal fan unit, and straight through to the
outside.

I hope you can turn it down!

Did you buy the optional wind tunnel attachment?



I thought the general consensus in this group was that two is better than
one! Or am I talking drivel?

On Mon, 23 Jan 2006 16:57:24 -0000, a particular chimpanzee named
"Grumps" randomly hit the keyboard and
produced:

We're having our kitchen extended and the architect has noted (on our
building plans) that we need an air extraction rate of 60 l/min. Question:
Can this all be catered for just using a cooker hood (extraction to the
outside), or does it need a 'higher up' fan?

First, your plans should say, "60 l/second", not 60 l/min.

Second, a cooker hood capable of extracting at least 30 litres/sec
will comply.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

"Hugo Nebula" abuse@localhost wrote in message
...
On Mon, 23 Jan 2006 16:57:24 -0000, a particular chimpanzee named
"Grumps" randomly hit the keyboard and
produced:

We're having our kitchen extended and the architect has noted (on our
building plans) that we need an air extraction rate of 60 l/min. Question:
Can this all be catered for just using a cooker hood (extraction to the
outside), or does it need a 'higher up' fan?

First, your plans should say, "60 l/second", not 60 l/min.

Yes, of course. They do! My typo.

Second, a cooker hood capable of extracting at least 30 litres/sec
will comply.

Why is this?

Second, a cooker hood capable of extracting at least 30 litres/sec
will comply.

Why is this?

It's in the regs. I believe it is because a cooker hood extracts from where
the steam and fumes are generated, so is considered to have the same
effectiveness as an extractor twice the size that might situated away from
the cooker.

Christian.

Christian McArdle wrote:
Second, a cooker hood capable of extracting at least 30 litres/sec
will comply.

Why is this?

It's in the regs. I believe it is because a cooker hood extracts from
where the steam and fumes are generated, so is considered to have the
same effectiveness as an extractor twice the size that might situated
away from the cooker.

Thanks.
Sounds logical. I wonder why my architect didn't mention this.
I don't suppose you know where abouts in the regs?

Sounds logical. I wonder why my architect didn't mention this.
I don't suppose you know where abouts in the regs?

Part F.

Table 1.1a Extract ventilation rates

Kitchen 30 l/s (adjacent to hob); or 60 l/s (elsewhere)
Utility room 30 l/s
Bathroom 15 l/s
Sanitary accommodation 6 l/s

Christian.