On 9 Jan 2006 06:45:17 -0800, a particular chimpanzee named
randomly hit the keyboard and produced:

I may have the opportunity to purchase some good condition used
double-glazed PCVu french doors. They are 5 years old. Will I have
problems with the building regs if I use them in a new extension ? What
if I can't prove what they are filled with etc.?

If you assume they're air-filled with no coating and you can establish
the gap between the panes, you can work out their U-value (from
Approved Document L1). The requirement is for an _average_ U-value of
2.0W/m²K where the area of opening is no more than 25% of the floor
area. There are trade-offs if the area of glazing is less than the
permitted or the other elements have a U-value less than the maximum.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"