Double and triple glazing

Windows and doors are often the weakest point in a home’s thermal envelope. Upgrading your glazing can significantly reduce heat loss, eliminate draughts, and even reduce outside noise.

Types of energy-efficient glazing

1. Double Glazing

This is the standard for modern UK homes. It consists of two panes of glass with a gap (usually 16mm or 20mm) between them. The gap is filled with an insulating gas like Argon to reduce heat transfer.

2. Triple Glazing

Contains three panes of glass and two gas-filled gaps. It provides even better thermal performance and noise reduction than double glazing.

  • Best for: Very cold climates or homes where noise reduction is a high priority (e.g., near a busy road or airport).

3. Secondary Glazing

This involves adding a second, independent pane of glass or plastic to the inside of an existing window.

  • Best for: Listed buildings or homes in conservation areas where you aren’t allowed to replace the original windows. It is also a much cheaper alternative to full double glazing.

Technical features to look for

When buying new windows, look for these features:

  • Low-E Glass: Glass with a special “Low-Emissivity” coating that reflects heat back into the room.
  • Warm-Edge Spacer Bars: The material that separates the glass panes. Plastic spacers are much more efficient than traditional metal ones.
  • Energy Ratings: Windows are rated from A++ (most efficient) to E. In the UK, new windows must be at least B-rated.

Costs and Savings

Replacing all the windows in an average semi-detached house with A-rated double glazing typically costs between £4,000 and £6,000.

While the energy savings (around £140 per year) are lower than for wall or loft insulation, new windows provide major benefits in terms of comfort, security, and property value.

Low-cost tip: If your double glazing is still in good condition but you feel a draught, you may just need to replace the rubber seals or adjust the hinges. This is much cheaper than replacing the entire window.

Window Maintenance

To keep your energy-efficient windows working at their best:

  • Check seals: Inspect the rubber gaskets around the frame for cracks or gaps.
  • Clean frames: Keep uPVC or aluminium frames clean to prevent grit from damaging the moving parts.
  • Lubricate hinges: Use a light oil twice a year to ensure the windows close tightly.