Double glazing is nothing but insulating glass that has a minimum of two or more glass panes. The glass panes are either separated by a vacuum or space filled with gas so that there is not much heat transfer from the building's envelope part around. These glasses are also helpful https://allen62.webs.com/apps/blog/show/47393813-perks-of-having-double-glazing-windows-installed-at-your-home-or-work-places