What Are Double Glazed Windows

Double glazed windows comprise two panes of glass which are separated by a gap. This gap in older style double glazed windows will usually be between 12mm and 16mm. In modern energy efficient new or replacement double glazing the gap will typically be 20mm.

The two panes of glass will typically be 4mm each giving an overall sealed unit size of 28mm. The sealed unit in modern double glazed windows systems will be filled with Argon gas. Because Argon gas is denser than air, adding it between the panes of glass improved the thermal efficiency of the window.

The sealed unit is then housed into a frame or a sash, these frames and sashes will be made from Timber, Aluminium or uPVC. The efficiency of the complete window system is assessed and to help chose the best window system for you BFRC (British Fenestration Rating Council) have created an energy rating scheme.

Double Glazed Windows are rated from A+ to G with G being at the bottom of the scale. The rating is calculated on the whole of the window which means that is it very important to ensure the quality of all components, not just the sealed unit.