DOUBLE GLAZED UNIT

A double glazed unit (also called a DGU or IGU) is two panes of glass sealed around a spacer bar with a sealed cavity between them. That cavity does the work: it slows heat transfer in both directions, so rooms stay warmer in winter and cooler in summer, and it cuts noise from outside.

We supply 20mm and 24mm units made to your measurements. The number refers to the total thickness of the unit, glass plus cavity plus glass. A 20mm unit is typically 4mm glass, a 12mm cavity and 4mm glass. A 24mm unit gives you a wider cavity or thicker panes, and better thermal and acoustic performance.

Double glazed units are sealed at manufacture and cannot be cut, drilled or modified afterwards, so the measurements need to be right the first time. The unit has to fit the rebate of your frame with the correct clearance. If you are unsure, your window supplier or glazier can confirm the sight size and rebate depth you need.

Replacing a failed unit? If you can see fogging or moisture between the panes, the perimeter seal has failed and the unit needs replacing rather than repairing.