normal double glazing windows is made from two layers of glass with air trapped in between them.
So How Can They Keep The House Warm ??
According to builders..."Double glazing works by trapping air between two panes of glass. This creates an insulating barrier that will stop heat being lost, "
"Double glazing keeps your house the at a constant temperature because there is a vacuum in between two layers of glass. There is no air or particles of any kind in a vacuum, so heat cannot be conducted through it. Therefore the heat inside the building cannot be lost to outside, and vice versa. "