In article ,
says...
I am about to but new upvc windows fitted with K glass double glazing.
I was amazed by the fact that 3 out of the 4 the vendors I contacted
asked me if I wanted to opt for K glass.
As far as I know K glass has to be the only option in view of the new
building regulations.
Apparently, there are still plenty of retailers trying to sell non K
glass units.
Does anyone know a foolproof way of identifying K-glass without
shelling 60 quids of so for some specialized equipment?

Thank,

Alex.

Do the "match test".
Look at a flame through the unit, you will see two images.
Both same colour = 'normal' glass
One darker than the other = Coated.
Rough and ready but accurate enough.

--
Ziggur

"S'ils te mordent, mords-les"