Cooker hoods: how to vent or not to vent?

[Amos]

Hi

After much conflicting advice from a number of people I thought I'd go after some more from you all :)

I need to install a cooker hood. The purpose of this is to:

1) Remove smoke/steam etc from the kitchen 2) Ventilate the kitchen: kitchen/diner gets too hot when/after cooking.

The hood will sit a fair distance (about 3m vert+horiz) from the outside wall, but directly on the (as yet unchecked) wall in front of the chimney flue.

The comments I have had are

1) There is no point in having 3m venting as it just doesn't work and is ugly. Should just do recirculating with carbon filter. 2) Recirculating no good at reducing heat. Should either vent or recirculate plus add a separate fan in the kitchen. 3) Separate fan doesn't work well as it doesn't extract from where the heat/smoke is produced. Should vent. Consider adding additional fan in vent to increase power. 4) Adding additional fan problematic as cannot control from hood. 5) Throughput with recirculation less than with venting due to filter obstruction.

In addition I was wondering if there is any point in venting to the chimney flue. Possible plus is the there may be a little draw from the chimney (even without a fire), and it would be a lot more attractive. Possible -ve is that smoke would just fall back down the chimney or vent would not cope, so it would be pointless.

I would really appreciate any helpful comments anyone has on these options, especially if any of the arguments are fallacious.

Thanks in advance.

Amos

[Grunff]

Recirculating will achieve neither. It will reduce smells to some degree, but that's all. All the heat, and more importantly the water vapour, stay in the kitchen.

This is not very far. Our vent has a total run of 2.5m and works great.

IMO recirculating hoods are only just very slightly better than nothing. Venting is far, far better.

The quality of the hood makes a huge difference to how well it extracts. We bought a twin fan hood from Elica, which works much, much better than our old Baumatic hood used to.

I'd recommend using a venting hood, and installing the biggest diameter duct you can. 5" is much better than 4".

I wouldn't consider that as an option - too many variables, and unlikely to work.

[Chip]

On Sun, 19 Jun 2005 17:14:33 +0100,it is alleged that Grunff spake thusly in uk.d-i-y:

Just to add to that, there is the fact that all hoods, even filtered ones will expel some grease and lots of moisture in the exhaust. Having that building up in a chimney over time is likely to be very bad odour wise and health wise, and may even cause condensation problems, so that's a definite no.

I would definitely go with vented. MUCH better than a recirc.:-)

[Rick]

Ugly is a matter of opinion, and how well you do the vent pipe

Recirculating will make the room wharmer, as you have the heat from the fan to add in

I think these fans look really ugly

Debatable

You could run the vent pipe right up the chinmey to the pot, but its hard work ...

[Andy Hall]

Agreed.

Take a look at a fairly powerful blower and 120mm or 150mm duct for this kind of length. Try to avoid sharp corners in the ducting by using the flexible type if possible.

Take a look at Elica, an Italian manufacturer. Elica make their own branded products plus virtually all for other vendors in Europe on a private label basis.

Their UK distributor is DR Cooker Hoods

site is useful for the catalogue.

DR don't supply directly but through resellers such as TLC Electrical and others. It's worth shopping around for best price.

I fitted one of their Built-in 80 Ultra models a couple of years ago and it's excellent.

It's well worth getting the kind with metal mesh grease filters because these can simply be taken out and washed.

[fred]

In article , Rick writes

That would be my choice, using a flexible stainless steel flue liner and a vent cap on top. 5" for a 2 storey or 6" for a town house, expect to pay

8-10quid a metre but worth it I think.

[Mary Fisher]

How do you know it doesn't work?

Mary

[Chip]

On Sun, 19 Jun 2005 20:02:01 +0100,it is alleged that "Mary Fisher" spake thusly in uk.d-i-y:

I read this as meaning this is an opinion from someone else, and we're being asked our opinion on this opinion :-)

[Mary Fisher]

Oh ... I THINK I know what you mean :-)

Mary

[Amos]

Good point. Mice are enough of a problem in Edinburgh flats already?

That was my feeling, so I was a little put out when I was told it wouldn't be effective. However I am glad to hear that everyone is pretty much consistent on this :)

Thanks

Amos

[Amos]

Thanks for all your comments. The twin fan hood - do you mean one with an additional external motor.

Elica seem to have quite a few 6" hoods. I'll probably go for that. It is a kitchen diner, so it really needs to be kept clear.

Thanks

Amos

[Grunff]

You're welcome. By twin fan, I mean one with two motors/fans within the housing, like the Concorde Twin

I'd be surprised if you don't get a good result with a decent hood.

[Christian McArdle]

Recirculating doesn't work. At all.

You can vent 3m no problem. However, you MUST use a centrifugal fan. An axial fan is not capable of doing it, as single stage axial fans can't produce sufficient compression. Use the largest ducting you can aesthetically fit.

Christian.

[Mathew J. Newton]

I recently fitted a Baumatic built-in extractor

which works

*extremely* well with a 4m ducting run (with a right-angle bend after the first metre) using 6" rigid ducting hidden in the ceiling void.

This particular extractor has a free-flow flowrate of 500m3/hr and, having gone through the back pressure figures and fan curves I calculate it now runs at ~400m3/hr.

Condensation in the kitchen and cooking smells in the rest of house are now a thing of the past, and for

[Mark]

Also use circular section ducting rather than "space-saving" rectangular section. BES stock a good selection.

Mark

[Christian McArdle]

And specifically avoid ribbed flexible ducting.

Christian.

[Chris Bacon]

You can also use grey soil pipe and fittings, which are cheaper.

[Amos]

Thanks. Actually, my mistake - it is actually 3m horiz + right angle + another metre and a half, so it is rather long.

Even so, in light of comments here, I will vent. thanks

Amos

Grunff wrote:

[Amos]

Call me stupid I could not find any at BES. I plan to use solid duct pipes rather than flexible. Although square makes a bit of a difference, given I cannot go invisible on that one, I might compomise for square.

Amos

[Amos]

Turns out Elica want to charge me 200 quid for the ducting. Ha ha.

However I don't really know what I should be paying. Any ideas for 1.5m

• 90 degrees + 3m + wall plate of 150mm diameter. I've got it down to

110, but that still seems stupidly high. What should I really be looking for and where. I am clearly missing something.

Thanks for any help.

Amos