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Triple Glazing has been around for many years, but until very recently most triple glazed products have incorporated 28mm thick units. This thickness is more commonly found in double glazed windows.

The triple glazed units within The Definitive Collection are 40mm thick. This dramatically improves thermal efficiency by up to 40% – a real saving in both energy and cash.

As such, this range truly qualifies as being one of the best high performance windows available in the UK and all of our triple glazed windows are backed up by a British Fenestration Ratings Council (BFRC) energy label.

Although many double glazed windows achieve an ‘A’ rating, the next generation triple glazed windows can significantly improve the energy efficiency of your home even further.

The Allweather Windows triple glazing range can help you save even more on your heating bills. Energy costs will almost certainly continue to rise and according to the Energy Savings Trust, a staggering 26% of all domestic heat loss escapes through windows.

Should we switch to triple glazing?

Now, a U-value of 1.6 may look good when compared to what we have been fitting relatively recently, but compared to the U-value demanded for walls – currently less than 0.3 and due to fall even lower – you can see that windows remain weak spots in the overall thermal efficiency of a building envelope. Hence the tremendous pressure to improve their performance even further.

The key benefits are really to do with comfort. If you insulate the walls, roof and floor of a house, and you ignore the glazing, you end up with cold spots surrounding the windows at night, which cause draughts, draw heat away from you if you sit next to them, and result in streams of condensation running down the panes. So, in essence, the standard of glazing has to match the standard of the insulation elsewhere in the house, so that the warm wrapping around the house performs consistently.

Which is where triple glazing comes in. Because if double glazing makes a modern house more comfortable to live in, triple glazing makes it even more so.


The physics involved here have been worked out in Germany by the PassivHaus Institute. It has shown what happens to surface temperatures on various forms of glazing when it gets really cold outside, and the internal air temperature is designed to be at 21°C:

  • Next to a single-glazed window, the internal surface temperature is around 1°C.

  • Next to a double-glazed window (2000 vintage), the surface temperature is around 11°C.

  • Next to a modern, energy-efficient double-glazed window, the surface temperature is 16°C.

  • Next to a triple-glazed window, with a centre-pane U-value of just 0.65, the temperature is 18°C.

So you can see that whilst a double-glazed window is perfectly adequate, a triple-glazed one is just that much more comfortable, because it hangs onto heat just that little bit better. So whilst triple glazing may make little difference to your heating bills, you will notice the difference inside the house.

The PassivHaus standard promotes the use of triple glazing for precisely this reason – i.e. comfort – although it also states that the frames themselves have to be insulated, and the windows need to be mounted in the correct location within the wall assembly.

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