Glass
Double-glazed units
A double-glazed unit is two panes of glass held apart by a spacer bar and sealed at the edges, with dry air or argon in the cavity. Made to BS EN 1279, it cuts heat loss and noise compared with single glazing, and fits into a frame as one component.
Where does it work well?
Heated shops, cafes, restaurants and offices where comfort, condensation and energy bills matter, particularly frontages with thermally broken frames that can take the full unit thickness.
Pros
- Lower heat loss than single glass
- Reduces condensation
- Each pane can be a different glass type
- Can reduce outside noise
Cons
- Thicker and heavier than single glass
- Edge seals eventually fail
- Frames need a deep enough glazing pocket
How long does it last?
Typically many years, with the edge seal usually the first thing to fail, particularly where water sits in the frame.
What should you check when buying?
Specify each pane separately, because door and low-level units need safety glass on the right faces. Ask for the overall thickness, spacer type and cavity gas, and check the frame has working drainage so that water does not sit against the seal.
Common questions
Do shop windows need double glazing?
Not always. Many shops still use single safety glass, and whether double glazing is needed depends on the work and the building. Ask building control what applies, especially for new buildings or a change of use.
Can a double-glazed unit go in a single-glazed frame?
Only if the rebate is deep enough and the frame can carry the extra weight. Many single-glazed shopfront frames have a narrow pocket, so you may need new beads or a new frame section.