wrote in message
ups.com...
We've just had a gas fire fitted in the living room and understand
there is a requirement for a vent. it's a victorian house which is far
from sealed and I intend to get a carbon monoxide alarm. We're most of
the way through fitting a secondary wood floor and the plan was to put
a vent into it to the underfloor cavity (we've recently made sure all
the air bricks to the cavity are clear).

So two questions:

1) Given the general draughtiness of the house do we really need the
air vent?

You need to allow for someone "draught proofing" it later.

2) if yes, how big. The figure of 100cm3 was mentioned but our local
hardware stores don't carry stock and the minimum order requriements
mean I'd look online.

Last time I checked (about 7 years) it was 16 sq in, which is about 100cm^2.

However the vents i've found (on
andyplumb.co.uk) are measured, strangely, in inches. I'm presuming
that 100cm3 does not equal a vent meauring 10cmx10cm but relates to the
size of the holes.

The area is the "free flow area" (ie area of holes) not the overall vent
dimension.

Don't muck around with this, do it right.

--
73
Brian, G8OSN
www.g8osn.org.uk