U-Values Explained – Why Are They important?


U-values measure how effective a material is as an insulator. The lower the U-value, the less heat is lost and the more insulation the material provides.

Old window glass is a very poor insulator and can leave your home feeling cold as well as costing you money.

At Energlaze we specialise in providing glazing solutions to increase the comfort of your home and lower your heating bills. Our new Low-E-Plus2™ heat-retaining glass has two invisible coatings (just like triple-glazing) and reduces U-values by as much as 80%. It is retrofitted into existing window frames so you save up to 50% on installation.

Woman saving on bills

Comparison Chart

The table shows the U-values of the various materials used in a building. Of all these materials, glass is the poorest insulator. You can see that more heat is lost through windows than the same area of wall.

Material TypeU- Value
RoofNo Insulation2.3
With Insulation0.4
Cavity WallNo Insulation1.6
With Insulation0.6
FloorNo Insulation0.9
With Insulation0.6
Solid Wall (block & plaster)2.3
Cavity Wall (block/polys/block)0.58
Cavity Wall (timber frame with above)0.46
Windows Single-Glazed5.8
Windows Old Double-Glazed (24mm)2.8
Windows Triple-Glazed (24mm)1.3
New Low-E-Plus2 (24mm)0.9