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