Double glazed uPVC windows and doors, are constructed by the addition of a uPVC (unplasticized Poly Vinyl Chloride) cover to a rigid frame, which is usually made of steel. Double glazed windows have two separate panes of glass instead of single panes with traditional windows. The two panes are bit spaced a from one another. The space between the panes is either a vacuum or is filled by a gas, such as argon, which enhances their insulating efficiency.