Just a small point: how can you tell if they're the wwrong way round?
I've just had some windows installed in my loft conversion, and I can
tell the builders got the bathroom windows back to front (patterned and
textured bit on the outside), but how can I check that the clear-glass
windows are the right way around?

Regards
Paul

Hmmm!

It,s all getting a bit technical now.

Historically, textured glass sealed units were installed with the texture
on the inside pane. However - in order to conform to the FENSA standards
many companies are using "K" (low E) glass to improve the overall U-value
of the window. The low E coating is only fully effective on flat glass
and is applied to the inside of the inside pane. Therefore if your
bathroom window has a combination of Texture glass and "K" glass the
Texture will be placed on the outside, harder to clean but more thermally
efficient.

How can you tell whether the clear glass windows are the right way round?
There is a simple test that you could do by looking through the unit at a
flame held on the inside BUT my advice would be to trust the installers.
Some sceptics might be surprised to learn that they usually get it right.

(But then I am biased )