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To put it simply – triple glazing is three panes of glass instead of one or two. We all know that adding a vacuum between two panes of glass produces a large improvement in thermal efficiency. By having an extra pane, you will increase efficiency and reduce noise. It’s already known that double glazed windows make a significant improvement compared to single glazing, so would making the jump to triple glazing make much of a difference?



While it might not be the perfect way of measuring insulation, the energy efficiency of a window can be roughly described using a ‘U-value’.   This value is calculated by dividing the transfer of heat per square meter (in watts) by the difference in temperature across the entire building. The lower this value is, the better.

Single glazing has a ‘U-value’ of 5, older double glazing about 3 and new modern double glazing a U-value of 1.6, which is mainly due to improved methods of double glazing compared to older models. These improvements include:

  • The cavity is filled with an inert gas – Argon is selected most often.  In situations where space is limited, the even more effective Krypton or Xenon may be used.
  • The use of low-emissivity (low-E) glass, which comes with a coating of metal oxide on the internal panes. This helps to limit the amount of heat that can flow in a given direction, allowing heat to enter your home, without escaping it.

All this has brought down the U-value of modern double glazed windows considerably, but triple glazed windows can offer us a U-value of 1 and even lower.  So, what are some things that may stop us from adopting it?

                    1. Cost

One of the clearest reasons is that triple glazing costs more than double glazing. Not only does it require more materials, but also more precise manufacturing conditions, and generates more errors.  Since triple glazing is heavier, the cost of shipping is also higher.

For example, a double glazed window that costs around £350 will set you back approximately £485 for exactly the same window with triple glazing. Of course, prices will vary depending on the style, size and frame material of the window.

                    2. Light penetration

 Adding an extra pane of glass will reduce the ability of light to break through the window.  With another pane added, the interior of the window will be dimmer.

                    3. Heat penetration

Walls and doors have higher U-ratings which makes windows the weak points in a building – and we should ensure they’re as efficient as possible.  But that’s not all – when the sun is shining, windows are able to allow heat to enter a house.  Modern double glazing actually allows windows to become net contributors to a building’s heating during the summer.

When we add more panes to a window, this advantage becomes dispensed, and we’re going back a step.

                    4. Noise penetration

A benefit of double glazed windows is its ability to exclude background noises such as distant traffic, which is great for a peaceful life indoors. Since double glazing can keep noise out, it may be assumed that triple glazed windows can do an even better job, but when compared to rival technologies like secondary double glazing, the noise-reducing power is not that much more impressive. Sound travels more easily through a solid than air, which takes away from the performance of triple glazing, since the extra pane adds more solid space.

                    5. Condensation

Many new owners of triple glazed windows are surprised to see condensation form on the outside pane of their windows.  This occurs as a consequence of low heat-transference; with less heat from the inside there to keep airborne moisture airborne, it will settle onto cold surfaces and condense.


If you already have new energy efficient double glazed windows, it is not worth switching to triple glazing. You will only experience minimal improvements to the energy efficiency of your home. In this circumstance, installing triple glazing is a poor decision and you will not see a return on your investment.


  • L. P. says:

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