Glazing Options

Secondary-glazing creates an air-gap by inserting a second pane of glass or other clear sheet behind an existing windowpane.

Double-glazing has 2 panes of glass (or a pane of glass and another clear sheet) spaced apart by a gap containing air or argon gas, (which is a better insulator than air).

This is then sealed to form an insulated glazing unit (IGU).

IGUs can have different insulation ratings. These depend on:

whether standard or low-emissivity (low-e) glass is used
the distance between the 2 panes
the type of gas (air or argon) in the gap.

The edge-seal of an IGU must not be allowed to remain wet. That means these units must be installed in a frame that allows free drainage of water.

The unit can be fitted either directly into new window frames or retro-fitted into an existing window frame once the original glass is removed.

“Triple” glazing
This is used mostly in Northern-Europe and North America, where winter temperatures get much colder than here. “Triple” glazing uses 3 sheets of glass to create 2 air-gaps. This gives even greater thermal performance – but it needs an extra-wide frame and creates a heavy window.