Sealed unit build-ups explained
How double and triple glazed units are made up: glass, spacer, gas and coatings.
What is a sealed unit?
Two or more panes of glass separated by a spacer bar and sealed around the edge, with a gas-filled cavity between them. It is also called an insulating glass unit or IGU.
What do the numbers mean?
A 4-20-4 unit has two 4mm panes and a 20mm cavity, 28mm overall. A triple unit such as 4-14-4-14-4 is 40mm overall.
What improves performance?
A low-E coating on the inner pane, argon gas in the cavity and a warm-edge spacer all reduce heat loss.
What standard applies?
Sealed units are made to BS EN 1279.
This guide is general information for trade customers. The person carrying out the work remains responsible for meeting the building regulations and any planning requirements for the specific job.