Richard Savage wrote on Tuesday (20/01/2004) :
Would like to hear your views/experiences concerning kitchen extractor
hoods. I'm planning my replacement kitchen and am debating the pros
and cons of extractor hoods that vent through an outside wall compared
with those that, by virtue of location on an internal wall must clean
and then recirculate the air.

Very definitely extract to the outside. The filter in a recirculating
type may take out some of the grease, but none of the moisture. I ran a
rigid plastic pipe up into the ceiling, then used flexible from there
about 5 feet along under the floor. I might have been lucky in that the
joists ran in the right direction to enable me to do this (check before
you decide). Some, perhaps all cooker hoods can be set to recirculate
or be ducted out.

I don't think the wasted heat should be considered, it is after all
foul moisture laden air which will do your home and its decorations no
good at all.

Make sure you get a wall outlet with a flap valve, to prevent air
blowing back in. I don't think there would be much likelihood of the
pipework ever needing cleaning out, during the working life of cooker
hood. The downside is that it is a lot more work putting the pipework
in.

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Regards,
Harry (M1BYT) (Lap)
http://www.ukradioamateur.org