On Sat, 18 Nov 2006 11:01:57 +0000 (GMT) Dave Plowman (News) wrote :
I'd hazard a strong guess that the DG units don't have trickle vents?

Aren't these required by 'law' these days?

They were but DCLG retracted the requirement last month. It now is

"3.4 Where the original windows were fitted with trickle ventilators the
replacement windows should include them and they should be sized as
set-out in paragraph 3.6.
It would be good practice to fit trickle ventilators (or equivalent),
with accessible controls, in all replacement windows to help with control
of condensation and improve indoor air quality."

http://www.communities.gov.uk/index.asp?id=1503738

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk