"Jonathan Tong" wrote in message
...

Hmmm, I hope not... I understood that current building regs requires
windows with U values of less than 2.0 to be installed.

I can confirm that. We are putting in some metal framed windows that only
take 4-6-4mm panes (eg 6mm spacer). To meet 2.0 we had to use coated glass.

Our DG is
apparently approx U=1.2 using Pilkington Optitherm (soft-coated glass),
argon filled and a super-spacer-bar-thingy. The units are called
Pilkington Insulights.

I believe Krypton is slightly better than Argon. Not too much more expensive
(if you can find someone who already has a cylinder of the stuff).