Hi

I Am just starting to refit our kitchen, there is a 9"x9" hole in the wall
(ducted straight to outside) where the previous owners removed the bricks
and didn't bother to put on a grill on the inside. As the first part of the
refit the old boiler has been ripped out, this had a conventional flue which
went straight up the chimney, the new boiler will be room sealed. I would
like to block up the hole in the wall as the wind howls through this and
keeps the kitchen cold (there is no rad), and it is probably too close to
where the new flue will have to exit the wall - could anyone clarify the
minimum distance for me? However I am aware that there are some
ventilation requirements for kitchens, so do I have to make another vent
somewhere else (presumably cavity sealed, ie ducted to outside) if I block
it and what size does it have to be? In addition there is no cooker
extractor at present, do I have to put one in or can I leave it without - as
it is now?

As an aside, what should I do about blocking the disused chimney, I would
rather seal this up, as I don't want a gaping hole above the new boiler, I
was just going to plasterboard across the entrance and make it part of the
existing alcove ceiling that the boiler sits in. If I do this do I need a
vent into the chimney stack to keep it dry, there is an existing hatch on
the outside, which I presume was for sweeping, I could easily put a grill on
this.

Cheers

Martin

On Fri, 10 Oct 2003 12:51:04 +0100, a particular chimpanzee named
"Martin Crook" randomly hit the
keyboard and produced:

...the new boiler will be room sealed... and it is probably too close to
where the new flue will have to exit the wall - could anyone clarify the
minimum distance for me?

A boiler flue should be at least 300mm between an opening for a
fanned-flue, or between 300mm-600mm to the side or above an opening
for a natural draught flue depending on the output (see diagram 3.4 of
AD 'J' [http://tinyurl.com/qjn7])

However I am aware that there are some
ventilation requirements for kitchens, so do I have to make another vent
somewhere else (presumably cavity sealed, ie ducted to outside) if I block
it and what size does it have to be? In addition there is no cooker
extractor at present, do I have to put one in or can I leave it without - as
it is now?

The ventilation opening would have been sized for the boiler rather
than for background ventilation, so it would be acceptable to reduce
the size of the vent opening to 4000mm² (IIRC, a 225mm x 75mm air
brick with a closeable grille, or trickle vents in a window)

You're not required to provide an extract fan if there isn't one
already, but as one who's lived in houses with and without them, I
would recommend that you do. The existing open-flued boiler acted as
an extract fan, and you may find that the condensation level will rise
once it's removed.

As an aside, what should I do about blocking the disused chimney, I would
rather seal this up, as I don't want a gaping hole above the new boiler, I
was just going to plasterboard across the entrance and make it part of the
existing alcove ceiling that the boiler sits in. If I do this do I need a
vent into the chimney stack to keep it dry, there is an existing hatch on
the outside, which I presume was for sweeping, I could easily put a grill on
this.

You definitely need to ventilate the chimney (usually by a small
grille internally); not sure if that should be by a grille in the
outside. I would have thought that might lead to problems by
introducing cold air into the flue causing (rather than removing)
condensation, and negating any stack effect.
--
Hugo Nebula
"You know, I'd rather see this on TV,
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