What is a U-Value?

Many people are confused about what a U-value is or why it is important.

In basic terms, a U-Value measures how good a material is at being an insulator. This means that it measures how effective they are from preventing heat from transmitting between the inside and outside of a building. The best insulating materials have U-Values close to zero – the lower, the better. A Low U-value also means there is low heat lose.

An example of some of the U-Values are:
• An uninsulated ceiling has a U-value of 2.3
• An insulated ceiling has a U-value of 0.16
• A single-glazed window has a U-value of 5.6
• A double-glazed window has a U-Value of 2.8

A U-value is measured in W/m2K. This translates to Watts/Meters Squared Kelvin. U-Values measures the rate of heat flow in Watts (W) through an area of 1sqm (m2) for a temperature difference across the structure of 1 degree centigrade or Kelvin (K).

Let’s look at an example of working out energy using U-values:
If you have a window that is 1m tall and 2m wide, it has an area of 2m2 and if your house has 10 windows that is an area of 20m2
The temperature inside the house is 20 Degrees and the temperature outside the house is 8 Degrees, meaning there is a temperature difference of 12 Degrees
The calculation would be:
2.8 x (20×12) = 2.8 x 240 = 672 W
Double-glazed windows produce 672 W of energy

U-Values are important so your property can be insulated with the most appropriate material. Performance measures have become more important as energy prices increase and by insulating your property with the most appropriate materials will help you in not paying large heating bills. When looking at how much energy is produced with U-values, you can decide whether or not insulating is a good idea.