Double vs Triple Glazing

Double or triple glazing – what’s the difference and is it worth the extra cost? Learn more about both options and make the right choice for your home.

What Is Triple Glazing

A triple glazed unit consists of 3 panes of glass with 2 sealed air gaps. Double glazing consists of 2 panes of glass with 1 sealed air gap. Compared to single glazing, an additional pane or panes of glass can improve the thermal performance of a unit, provided that the quality of materials and specification are correct.

Thermal performance is measured in terms of heat loss and is expressed as a U-value. The lower the value, the better the insulator.

Some windows and doors are tested by the British Fenestration Rating Council who operate a system similar to that seen on fridges and freezers. ‘E-rated’ represents the least efficient product and the system continues D, C, B and so on with energy efficiency getting better with each letter change.

The ‘Best Option’

In places like Scandinavia where the climate is that much colder, triple glazing is pretty much the standard. But here in the UK, triple glazing has only recently begun to gain more traction and is increasingly marketed as the ‘best option’ for homeowners.

Whilst triple glazing offers a range of benefits, it may well not be the best option for your home. Triple glazing is ideal for newly constructed energy saving buildings where all parts, from the floor to roof, are chosen for their low u values and compliment each other.

When it comes to replacement windows for a standard built property, energy efficient A-rated double glazing is the perfect solution. The exception to this and where we may well recommend triple glazing is when a property is subject to noise pollution.

The Comparison To Watch Out For

You’ll have no doubt come across images in the style of the one below, where the heat loss of two houses is compared. The house with double glazing probably shows glowing red windows which indicates high heat loss. Whilst the house with triple glazing has glowing green windows indicating lower heat loss. Put like this, triple glazing looks amazing doesn’t it and who wouldn’t favour it?

Heat Loss

Is All As It Seems?

The truth behind a lot of those images is often in the specification small print which usually goes unread. In one popular example, the double glazing being used in the comparison is only ‘C-rated’ – this is the absolute minimum required by building regulations for new and replacement windows. So of course, triple glazing is going look amazing by comparison.

As you’ve probably discovered, a lot of companies offer ‘A-rated’ double glazing as standard. When this is compared to triple glazing it’s a different story and the improvement in thermal efficiency can be minimal.

In Conclusion (Triple Glazing)


  • Excellent sound insulation – ideal for noisy areas.
  • Extremely beneficial when installed as part of an energy saving build.
  • Improved security thanks to the third pane.
  • Improved thermal efficiency, but maybe not enough to justify the extra cost if being fitted into a standard building.


  • Generally more expensive than double glazing.
  • Higher initial costs can result in a longer term return on investment.
  • The third pane can reduce light entering a room.
  • Condensation can appear on the outer layer of glass.
The Ultimate Question – Double or Triple Glazing?

Of course, the choice is ultimately yours. Our advice would be that if you’re replacing windows in a standard built property, where noise isn’t an issue, A- rated double glazing is a perfectly acceptable solution.

If one of the key reasons you’re looking to replace your windows is because of noise pollution, then you should seriously consider triple glazing. Another reason to consider triple is if you are constructing an energy saving building.

Check out our How To Buy Double Glazing post to learn more about what to look for and what to avoid.

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