Double glazing wiki
Here is the double glazing definition:
Double glazing is also known as insulated glazing and was invented nearly two thousand years ago by the Romans to help prevent excessive heat loss from there bath houses which were situated in colder climates.
As the term “double glazing ” suggests, it consists of two panes of glass, separated by a gap. In modern double glazing the optimum gap is recommended to be around 16mm and is filled with an inert gas to further reduce heat loss.
Modern double glazing is available in a range of finishes with the most popular being white uPVC (Unplasticised Polyvinyl Chloride) which is a hard wearing, heavy duty building material popular for windows.
Over recent years the quality of the glass used for the panes has begun to change to offer higher level of heat retention efficiency. Some of the best quality windows have differing types of glass, one for internal and one for exterior to maximise the window’s energy efficiency. These energy saving sheets of glass work in partnership to encourage outside heat in and to keep inner heat inside.