A U Value is known as thermal transmittance, which is the rate at which heat transfers through a structure, such as a windows, glazed doors and conservatories, divided by the temperature difference of that structure.
It can be complicated to understand fully what U values are but the most important thing is to know which thermal performance scores to look for. There is a full spectrum of numbers, but when looking at U Values, the rule of thumb is that the lower the U-value, the better.
With Bluemanor's double-glazed windows, you can achieve U Values as low as 1.3 as standard with our double glazing and values as low as 0.93 with our triple-glazed windows.