"YAPH" wrote in message
...
On Thu, 26 Feb 2009 08:58:58 +0000, Arfa Daily wrote:

So what has changed ?

The industry assessment of undersized ventilation. Until about the middle
of last year anything over about half the correct ventilation was OK
(technically "Not to Current Standards") provided the appliance seemed to
be working OK. Now it's got to be spot on (less a few percent allowance
for margin of error). It's not Brutish Gas' decree but the industry
generally, in response (apparently) to an increase in Carbon Monoxide
incidents due to undersized ventilation. (I would guess this may be
connected with more people putting in uPVC windows and laminate flooring
which cut out much of the 'adventitious' ventilation one got from draughty
wooden windows and floors.)

Is the problem that the rules are evolving to assume the house is sealed and
only explicit ventilation is relevant? Is there no correction for eg a
draughty house, where the ventilation could well be more than adequate? Can
the rules be based on measurements of air flow rather than just sizes of
holes?