I am in the process of setting up a new kitchen and I am getting frustrated
about range hoods. I want a range hood that really works (ie extracts
smoke, smells and steam efficiently) but I cannot afford to pay the earth.

Appliance shops deluge you with sales bull and explain nothing. You can get
a hood from $200 to $2000. Some of the larger and fancier ones have more
stainless steel and bells and whistles but some look just the same and have
a price tag twice (or half) as much. When asked to explain the difference
you get "the more expensive one is better" if you ask better in what way
exactly you get told about features but not performance. I can make my own
jugements about ease of cleaning and if I need frisbees on the thingajig or
gold plated whatsernames.

I have looked at professional cooking gear web sites but so far it seems
that you have to have qualifications in air conditioning engineering to
follow their specs and most of the products assume a restaurant sized
operation.

One web site recommends that the hood be able to extract between 6 and 12
times the volume of the room per hour. That is you turn over the air every
5 to 10 minutes, this seems reasonable to me.

Does anybody have any views on that? Under what circumstances would the
upper or lower rate be appropriate?

How else might one assess the required rate?

David

>"David Hare-Scott"
>
>I am in the process of setting up a new kitchen and I am getting frustrated
>about range hoods. I want a range hood that really works (ie extracts
>smoke, smells and steam efficiently) but I cannot afford to pay the earth.

The only truly efficient range hoods vent to the outdoors. Essentially only
you can assess your budget... but efficient exhaust systems can cost as little
as US$200... and after that the sky's the limit. Without knowing the exact
configuration of your kitchen no one can offer more than wild speculation as to
which style to obtain and installation costs. Good luck.


---= BOYCOTT FRANCE (belgium) GERMANY--SPAIN =---
---= Move UNITED NATIONS To Paris =---
*********
"Life would be devoid of all meaning were it without tribulation."
Sheldon
````````````

"David Hare-Scott" > wrote in message
...
> I am in the process of setting up a new kitchen and I am getting
frustrated
> about range hoods. I want a range hood that really works (ie extracts
> smoke, smells and steam efficiently) but I cannot afford to pay the earth.
>
> Appliance shops deluge you with sales bull and explain nothing. You can
get
> a hood from $200 to $2000. Some of the larger and fancier ones have more
> stainless steel and bells and whistles but some look just the same and
have
> a price tag twice (or half) as much. When asked to explain the difference
> you get "the more expensive one is better" if you ask better in what way
> exactly you get told about features but not performance. I can make my
own
> jugements about ease of cleaning and if I need frisbees on the thingajig
or
> gold plated whatsernames.
>
> I have looked at professional cooking gear web sites but so far it seems
> that you have to have qualifications in air conditioning engineering to
> follow their specs and most of the products assume a restaurant sized
> operation.
>
> One web site recommends that the hood be able to extract between 6 and 12
> times the volume of the room per hour. That is you turn over the air
every
> 5 to 10 minutes, this seems reasonable to me.
>
> Does anybody have any views on that? Under what circumstances would the
> upper or lower rate be appropriate?
>
> How else might one assess the required rate?
>

You might ask over at rec.food.equipment. This is a much discussed topic.
Most people agree that the hood should be larger than the cooking surface.
The capacity in CFMs is dependant on the BTUs and the type of cooking. If
you are going to grill, then you should error on the larger end. For
typical cooking on a typical residential range you probably need between 600
and 1200 CFM. If your house is new and very tight, you can create dangerous
downdrafts in chimneys (fireplace, water heater, furnace,) if the hood is
too large and you don't have a source of make-up air. One rule of thumb
that I have seen is that you need 10 CFM per 1000 BTU of output from the
stove. On thing to keep in mind is that the ratings for hood drop as you
increase the length of duct and for each change of direction. There is also
a drop associated with the resistance of the damper that terminates the
duct.

"Vox Humana" > wrote in message
...
>
> You might ask over at rec.food.equipment. This is a much discussed topic.

Thanks I will try their archives first.

> Most people agree that the hood should be larger than the cooking surface.

This is hard to arrange since hoods come in the same sort of size as
cooktops, I suppose if I had a 60cm cooktop I could use a 90cm hood but I
have a 90cm cooktop.

> The capacity in CFMs is dependant on the BTUs and the type of cooking. If
> you are going to grill, then you should error on the larger end.

Agreed

For
> typical cooking on a typical residential range you probably need between
600
> and 1200 CFM.

Using the 12 times room volume per hour rule of thumb I get 230 CFM, hmmmm

If your house is new and very tight, you can create dangerous
> downdrafts in chimneys (fireplace, water heater, furnace,) if the hood is
> too large and you don't have a source of make-up air.

My house will be very tight so I will keep this in mind.

One rule of thumb
> that I have seen is that you need 10 CFM per 1000 BTU of output from the
> stove.

I will have to work on this one.


On thing to keep in mind is that the ratings for hood drop as you
> increase the length of duct and for each change of direction. There is
also
> a drop associated with the resistance of the damper that terminates the
> duct.
>
The tube will go straight out the wall behind the stove, a total length of
about 60cm (2ft) so these effects will be minor

David

"David Hare-Scott" > wrote in message
...
>
> "Vox Humana" > wrote in message
> ...
> >
> > You might ask over at rec.food.equipment. This is a much discussed
topic.
>
> Thanks I will try their archives first.
>
> > Most people agree that the hood should be larger than the cooking
surface.
>
> This is hard to arrange since hoods come in the same sort of size as
> cooktops, I suppose if I had a 60cm cooktop I could use a 90cm hood but I
> have a 90cm cooktop.

In the US, cooktops and ranges generally come in widths from 24 to 60 inches
in 6 inch increments as do hoods. For a 36 inch range, you would order a 42
inch hood.

"Vox Humana" offers:
>
>In the US, cooktops and ranges generally come in widths from 24 to 60 inches
>in 6 inch increments as do hoods. For a 36 inch range, you would order a 42
>inch hood.

That's pretty stupid (and will look stupid too)... an exhaust hood should be
[approximately] the same size as the cooking area... it's far more advantageous
to over-engineer the air volume movement than the hood size.


---= BOYCOTT FRANCE (belgium) GERMANY--SPAIN =---
---= Move UNITED NATIONS To Paris =---
*********
"Life would be devoid of all meaning were it without tribulation."
Sheldon
````````````

On Sat, 26 Jun 2004 07:57:54 GMT, "David Hare-Scott"
> wrote:

> if you ask better in what way
> exactly you get told about features but not performance.


Ask them how many CFM (cubic feet per minute) of air the
hood moves. Calculate the cubic feet in the area you're
venting and take it from there.

To further confuse you, have you considered an "exterior"
mounted fan?

More food for thought
http://www.fantech.net/rhl.htm


Practice safe eating - always use condiments

"sf" > wrote in message
...
> On Sat, 26 Jun 2004 07:57:54 GMT, "David Hare-Scott"
> > wrote:
>
> > if you ask better in what way
> > exactly you get told about features but not performance.
>
>
> Ask them how many CFM (cubic feet per minute) of air the
> hood moves. Calculate the cubic feet in the area you're
> venting and take it from there.
>

I can do all the required sums and most manufacturers specify the volume
extracted, the thing that I am having trouble with is the basis for
calculation of the desired rate of extraction.

> To further confuse you, have you considered an "exterior"
> mounted fan?
>

Since my duct will be very short, about 60cm (2ft) I cannot see that the
position of the fan will make much difference but please enlighten me if I
am wrong.


> More food for thought
> http://www.fantech.net/rhl.htm
>
This site is interesting, they give a rule of thumb for bathrooms of 8 air
changes per hour but I cannot find anything on kitchens.

David

On Sun, 27 Jun 2004 07:53:36 GMT, "David Hare-Scott"
> wrote:

>
> "sf" > wrote in message
> ...
> > On Sat, 26 Jun 2004 07:57:54 GMT, "David Hare-Scott"
> > > wrote:
> >
> > > if you ask better in what way
> > > exactly you get told about features but not performance.
> >
> >
> > Ask them how many CFM (cubic feet per minute) of air the
> > hood moves. Calculate the cubic feet in the area you're
> > venting and take it from there.
> >
>
> I can do all the required sums and most manufacturers specify the volume
> extracted, the thing that I am having trouble with is the basis for
> calculation of the desired rate of extraction.
>

Basis? Is this one big room? If so, calculate that.

> > To further confuse you, have you considered an "exterior"
> > mounted fan?
> >
>
> Since my duct will be very short, about 60cm (2ft) I cannot see that the
> position of the fan will make much difference but please enlighten me if I
> am wrong.
>
Noise.
>
> > More food for thought
> > http://www.fantech.net/rhl.htm
> >
> This site is interesting, they give a rule of thumb for bathrooms of 8 air
> changes per hour but I cannot find anything on kitchens.
>
You can't extrapolate?


Practice safe eating - always use condiments

"sf" > wrote in message
...

> >
> > I can do all the required sums and most manufacturers specify the
volume
> > extracted, the thing that I am having trouble with is the basis for
> > calculation of the desired rate of extraction.
> >
>
> Basis? Is this one big room? If so, calculate that.

We don't seem to be on the same wavelength here. I can calculate the volume
of the the room, I know what the heating capacity of my cooktop and oven
are. The question is what is the basis of computation of the required
extraction rate to service that room?


> > >
> > This site is interesting, they give a rule of thumb for bathrooms of 8
air
> > changes per hour but I cannot find anything on kitchens.
> >
> You can't extrapolate?

No I cannot. I don't have a 50 Mj gas stove in the bathroom. I don't fry
and produces any smoke in the bathroom. Please explain how to extrapolate
from bathrooms to kitchens.

David

On Mon, 28 Jun 2004 09:07:17 GMT, "David Hare-Scott"
> wrote:

>
> "sf" > wrote in message
> ...
>
> > >
> > > I can do all the required sums and most manufacturers specify the
> volume
> > > extracted, the thing that I am having trouble with is the basis for
> > > calculation of the desired rate of extraction.
> > >
> >
> > Basis? Is this one big room? If so, calculate that.
>
> We don't seem to be on the same wavelength here. I can calculate the volume
> of the the room, I know what the heating capacity of my cooktop and oven
> are. The question is what is the basis of computation of the required
> extraction rate to service that room?
>
You're making it harder than it is. How many cubic feet of
air do you want moved per minute? Take it from there.
>
> > > >
> > > This site is interesting, they give a rule of thumb for bathrooms of 8
> air
> > > changes per hour but I cannot find anything on kitchens.
> > >
> > You can't extrapolate?
>
> No I cannot. I don't have a 50 Mj gas stove in the bathroom. I don't fry
> and produces any smoke in the bathroom. Please explain how to extrapolate
> from bathrooms to kitchens.
>
cfm is your friend. If that's too hard for you, go to a
restaurant and find out what they use. I'm sure it will
meet your requirements.


Practice safe eating - always use condiments

On Sat, 26 Jun 2004 07:57:54 GMT, "David Hare-Scott"
> wrote:

>I am in the process of setting up a new kitchen and I am getting frustrated
>about range hoods. I want a range hood that really works (ie extracts
>smoke, smells and steam efficiently) but I cannot afford to pay the earth.

Another thing to think about is noise. The hoods are rated in "sones"
according to how quiet they are. That's also important to me in my
tiny house.

Good luck. I have one picked out but getting someone to install it is
a problem.

http://www.broan.com/product-detail.asp?ProductID=1124

Sue(tm)
Lead me not into temptation... I can find it myself!