When you start to get into the technical specifications of replacement windows you will probably come across terminoligy you?ve not heard of before, or don?t understand.? U-Value may well be one such example.

Put simply, the U-Value is how the insulation properties of the window are measured.? We have added a new page explaining it fully to help you understand what it is and why it?s important.

View our double glazing u-value explained page.

We aim to give you the facts about double glazing so that you can make a more informed decision.? If you have any feedback we?d love to hear it.

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