normal double glazing windows is made from two layers of glass with air trapped in between them.

Question

So How Can They Keep The House Warm ??

Answer 1

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. "