Replacement Windows

How a double glazed unit is built?

Components of double glazing

The double glazed unit (DGU), which fits within a window frame, is comprised of seven components:

  1. A Spacer Bar – a frame that separates the two panels of glass, creating a cavity. The spacer bar can be aluminium or warm-edge.
  2. Desiccant – a silicon material used in the spacer bar to dry up moisture trapped within the cavity
  3. A primary seal – the main barrier to air or moisture migration into the double glazed unit (DGU)
  4. The glass – clear, solar control, Low E, self-cleaning, acoustic, toughened, laminated or a combination
  5. The secondary seal – the main structural adhesive around the outside edge of the unit, holding all the elements together
  6. The cavity – the void formed between the component parts
  7. The gas filling the cavity – dehydrated air, argon, krypton or xenon.

Positioning of specialist glass within a double glazing window

A double glazing window has four faces.
Face 1 – the outer pane, atmosphere side
Face 2 – the outer pane, cavity side
Face 3 – the inner pane, cavity side
Face 4 – the inner pane, room side

It is important that specialist types of glass, such as Low E or self-cleaning, be positioned on specific faces within the double glazing window when a window replacement is made. For example:

  • Self cleaning glass must always be positioned on the outer pane, with the coating on phase 1.
  • Solar control glass should be positioned on face 2 of the double glazing window.
  • Low E glass can be used on either the inner or the outer pane - but the coating must always be on face 2 or 3 of the unit.





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