On 25 Jan, 15:24, Tony Bryer wrote:
On Thu, 25 Jan 2007 13:52:16 +0000 Dave Fawthrop wrote :

Yes! Normal double glazed windows have the *facility* to be locked
totally closed or slightly open. IMO much better than trickle vents.I'm not so sure. ISTM that on ground floor windows locked slightly open
is akin to a notice saying "insert crowbar here".

I agree, not the best for security.
But the point is just to get the BCO satisified with the required area
of trickle ventilation per window without a huge air brick in the wall.
If I want ventilation in reality I am must more likely to open a single
high-up window that go round opening all the windows to the vent
position !
One of the advantages of double glazing (although not optimized for
this) is sound insulation. So the "hole in frame" types of vents are
not for me. Plus they make PVCu windows even more ugly.
Cheers all,
Simon.