Energy Efficiency and U-value


What is U-value?

U-value is also often referred to as «thermal transmittance», which refers to the rate at which a structure allows the transfer of heat energy, divided by the temperature difference on either side of the structure.

Therefore, U-values are essentially a measure of the effectiveness of a material’s insulation. When this value is lower, it means that the material is considered as performing more efficiently as an insulator against heat loss from an internal space, than when it is a higher value.

U-value is measured in W/m²K. The average cavity wall will have a U-value of around 1.6 W/m²K, whereas a wall built of solid brick will be lower at around 2.0 W/m²K. For a window, this can rise to around 2.8 W/m²K. This is typical for existing dwellings, but many countries now have guidelines regarding the maximum allowed U-value that a new build window may have.


What’s the difference between U-value and R-value?

These two things are essentially the same, but with different applications. When talking about insulation within walls or ceilings, the industry favours R-value. When we talk about windows, we talk about U-value. R-values that are high are considered better insulators, whereas for U-values, the insulation is better the close the number is to zero.

How does U-value rating affect your home?

As U-value refers to the rate at which heat is lost through your windows, it is essentially a measure of your home’s energy efficiency. If your windows have a poor (high) U-value, then you are wasting energy that could be saved through the installation of better quality windows.

By installing new-build windows such as those manufactured by Blue Sky Windows, you can improve your U-value and as a direct result, your home’s ability to retain heat, which means that it will cost you less to heat your home. This will in turn lead to a reduction in energy bills for heating.

How Can I Improve my U-Value?

Blue Sky Windows only use the highest quality components from German manufacturers in producing doors and windows to your specification. Windows in old-builds often have an average of 8 to 10 W/m²K, which means that you’ll be losing a great deal of heat through your windows. Due to industry requirements, it is not typical to have a U-value any higher than 1.6 W/m²K in newly-installed windows.

All windows built by Blue Sky Windows are optimised to have as low a U-value as possible, which means you’ll immediately be improving the energy efficiency within your home. As a bonus, you’ll also be better insulting yourself against disruption from noise outside the home, for example traffic, railways or noisy neighbours, and protection against extreme weather.