In article , Janet Tweedy
writes

One consideration that we never found much info about was whether to go
for double glazing, would this cut down the cost of heating?

Yes, it would, if you are heating it significantly in the winter.

Eden do a
cheap range with poly carbonate glazing that's twin walled but not sure
if that would be a good option to go for. If double glazing is so good
how come many of the manufacturers don't offer it?

Because most gardeners don't heat their greenhouses through the winter?
It's only cactus growers and similar who tend to heat their greenhouses
significantly (i.e. maintaining a temperature of 40 deg F or
thereabouts) as opposed to merely maintaining it frost-free.


--
Kay
"Do not insult the crocodile until you have crossed the river"