If triple glazing is so good why aren’t the triple glazed units fitted to every window?

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Normally it’s a sales person or manufacturer that is telling you that the triple glazing is so much better because they can charge you more for it!

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The reality is that poor quality triple glazing can be worse than a double glazed unit. This means that the true answer to “which is better, double or triple glazing?” is very complicated.

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Generally people are considering the thermal and noise benefits of the glazing when they are asking about triple glazed units. It may seem a little strange, but it is the argon filled gap that provides the main benefit not the glass.

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Double glazed units started at 20mm with 4mm glass 12mm gap and 4mm glass. This was changed to 24mm which had a 4 + 16 + 4 combination. Modern DGU (double glazed units) are 28 mm. (4 + 20 + 4).

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If you are looking at triple glazing that is 28mm wide you end up with 4 + 8 + 4 + 8 + 4 – this is going to be less efficient that the double glazed unit.

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To get the full benefit of triple glazing you should be looking at 44mm units. This is 4 + 16 + 4 + 16 + 4.

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Full, quality triple glazed units can improve the thermal efficiency by 20 – 30%. This shifts an A+ double glazed unit to A++ triple glazed unit. The U value of a double glazed unit is around 1.3 this is lowered to 1 with triple glazing. Another benefit of triple glazing is that triple glazing can reduce the amount of condensation.

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Why should you consider triple glazing?

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Triple glazing is a lot more expensive than double glazing. It is a sensible choice if it reduces your bills by more than the difference between the double glazed units. Calculations should by done over a twenty year period.

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It should also be considered if it offers you environmental benefits – such as reduced noise levels.

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If you are next to a school and want to reduce the noise then you may want to consider triple glazing. Exposed properties with north facing windows would also benefit from triple glazing.

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Please note that if you have a property with 20mm double glazing you will really notice a difference with 28mm units. However, this would mean replacing the frames in most cases.

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